MAN-3A display

[Charles via cctalk]

Looking for a couple of MAN-3A (single character, seven-segment red LED 
display) to restore a '70's pocket calculator.


One digit is missing a segment. I had another 3A in my LED drawer - and 
IT has a different bad segment... aargh.


No luck searching the usual places online.

Can anyone help?

thanks.

[cctalk] Searching for a few good TI Silent 700 parts

[Charles via cctalk]

I have a Silent 700 terminal that only needs a printhead (several 
missing pixels on mine) and three keyswitches (I have the keytops so it 
doesn't matter which ones).


My other 700 is fully functional and it'd be nice to finish fixing the 
other one too! Can anyone help?


thanks

Charles

[cctalk] Re: Searching for a few good TI Silent 700 parts

[Charles via cctalk]

In fact it is a 745 :) If the printhead has all its pixels working, I'd 
like to buy it.


No keyboard at all, or just nonfunctional? Those particular keyswitches 
seem to be unobtainium nowadays...


thanks

Charles

On 12/24/22 12:00, cctalk-requ...@classiccmp.org wrote:

Message: 2
Date: Fri, 23 Dec 2022 10:56:19 -0800
From: Sellam Abraham
Subject: [cctalk] Re: Searching for a few good TI Silent 700 parts
To: "General Discussion: On-Topic and Off-Topic Posts"

Message-ID:

Content-Type: text/plain; charset="UTF-8"

Hi Charles.

Which specific model?

I have a 745 sans keyboard that can be parted out further.

Sellam

On Fri, Dec 23, 2022, 10:54 AM Charles via cctalk
wrote:


I have a Silent 700 terminal that only needs a printhead (several
missing pixels on mine) and three keyswitches (I have the keytops so it
doesn't matter which ones).

My other 700 is fully functional and it'd be nice to finish fixing the
other one too! Can anyone help?

thanks

Charles

[cctalk] Thinking of selling my 11/23+

[Charles via cctalk]

Is there any interest in my working 11/23+ system? I rarely run it any 
more, but don't know what it's worth.


Corporate cabinet, VT220 console, 4 MB RAM, two RL02 drives (RT-11XM, 
TSX-Plus 6.50), interface for 3.5" floppy drive, 16 serial ports.


Located in south central Missouri so pickup would be greatly preferred :)

thanks

Charles

RE: 400 Hz

[Charles via cctalk]

On 5/8/21 12:00 PM, cctalk-requ...@classiccmp.org wrote:
Message: 8 Date: Fri, 7 May 2021 21:59:08 + From: W2HX 
 To: Andrew Back , "General 
Discussion: On-Topic and Off-Topic Posts"  
Subject: RE: 400 Hz Message-ID: 
 
Content-Type: text/plain; charset="utf-8" I will add that aircraft are 
one of the main users of 400 Hz. This is because weight is always an 
critical design consideration. So with smaller transformers, smaller 
capacitors, etc, you can save a LOT of weight on electronic devices in 
an aircraft. 73 Eugene W2HX -Original Message- From: cctalk 
 On Behalf Of Andrew Back via cctalk 
Sent: Wednesday, May 5, 2021 11:26 AM To: cctalk@classiccmp.org 
Subject: Re: 400 Hz On 05/05/2021 16:07, Grant Taylor via cctalk wrote:

Were the higher frequencies used because it directly effected the
amount of time / duration in (fractions of) seconds between peaks of
rectified (but not yet smoothed) power?

Haven't read the rest of the thread and so at the risk of being profoundly 
wrong... Benefit of 400Hz mains is that transformers can be much smaller. Think 
of switching power supplies that rectify to DC and then switch up into kHz, 
which are then able to use far smaller transformer cores than an old linear 
PSU. At least this is a key motivation with 115V/400Hz 3-phase aviation power 
AFAIK.

By coincidence we've just built a big 28VDC power supply, so that we can run a 
vintage 400Hz aircraft rotary inverter, which will then be used to power up old 
mil surplus kit that wants this. A classic adventure in yak shaving. Anyway, 
here's the 28VDC bit.

https://www.rs-online.com/designspark/constructing-a-high-current-28v-dc-power-supply



That's a very neat repackaging of the Lambda power supplies! Do they 
have the surge capability to start that rotary inverter (which may 
require a LOT more than 44 amps until the armature gets moving)... I 
hope you tested them first ;)


I bought a 1 KVA 115V 400 Hz supply, a PP-7482/G from Fair Radio back 
when they still had them ("Reparable") a few years ago. The H-bridge 
TO-3 transistors were all blown, some with holes melted through their 
lids. I replaced them with BUX48A parts and it works again. It really 
sings that A-flat though ;)


But I don't have anything to run with it! When I was young, 400 Hz 
surplus gear was a dime a dozen because no one had 400 Hz power. Now I 
do and all that gear has disappeared...


-Charles

WB3JOK/0 since '76 :)

Re: ISO Laserjet I/II/III firmware

[Charles via cctalk]

On 8/13/21 7:00 PM, cctalk-requ...@classiccmp.org wrote:

Message: 1
Date: Thu, 12 Aug 2021 13:10:43 -0400
From: Ethan Dicks
To: Al Kossow,  "General Discussion: On-Topic and
Off-Topic Posts"
Subject: Re: ISO Laserjet I/II/III firmware
Message-ID:

Content-Type: text/plain; charset="UTF-8"

On Thu, Aug 12, 2021 at 10:48 AM Al Kossow via cctalk
  wrote:

I suspect interest in emulating them will die out once they get past the 68000 
models.

I may still have a II, and I definitely still have at least one
(functional) III and a 4Si

I still use my 4M/L all the time - Postscript + LocalTalk + IEEE1284.
It's a great little printer.

-ethan


I have a IIp+ that I got for $2 at a hamfest around 15 years ago... I 
have repaired it several times (most recently, visibly bad electrolytics 
in the switching PS startup circuit). In fact that's the second time the 
power supply has failed - the first time was years ago and I just 
replaced the board. Now it's crinkling the bottom of pages... there used 
to be a kit to fix that.


I love those old "bricks". Although mine is like my grandfather's axe 
(new head and new handle but it's still my grandpa's axe) :)


The trick nowadays is finding toner cartridges that weren't just 
refilled, but actually rebuilt (with a new wiper blade).


-Charles

Looking for Delphi software "Diag Tool"

[Charles via cctalk]

I have a 150cc scooter with a LiteOn MC21 fuel injection ECU that is 
malfunctioning. My search for a replacement brain has been unsuccessful. 
LiteOn became Delphi which is now part of Borg Warner and I don't see 
anything for download (or even purchase).


All I've been able to find online is the "Delphi Small Engine Management 
System Service Manual" from 2008, which refers to an apparently 
Windows-based program referred to only as "DIAG TOOL". It can display 
running engine parameters and malfunction codes, although it does not 
appear to be capable of reflashing the ECU.


I'm waiting for a connector kit to come from Amazon (probably via China) 
so I can rig it up on the bench with simulated inputs. The unit is 
potted in silicone rubber which will be a PITA to remove. I found this 
Ukranian site where a member had the fuel injector driver transistor 
fail (in his case, shorted) - 
http://geon-club.com.ua/forum/viewtopic.php?f=35&t=5735



If that's my problem it's failed open, but I'm not going to mutilate the 
box until I get it powered up on the bench...


Any help with anything relating to the MC21 EFI would be greatly 
appreciated. Thanks!

Re: Overclocked TI Silent 703 at 1200 bauds?

[Charles via cctalk]

Please excuse the hijack:

I have two Silent 700's, I think the 745 models with acoustic coupler 
and 110/300 baud rocker switch. One I have fixed and it works great 
(well, at least as far as that silvery thermal printout goes).


Unfortunately one has three bad keys and at least one missing column on 
the printhead (yes, the head itself is bad). Does anyone have a junker 
from which I can buy three keyswitches and a printhead? :)


thanks

Charles

Looking for HP Laserjet IIp+ power supply

[Charles via cctalk]

The main power supply for my ancient Laserjet IIp+ printer has given up. 
Fuse is not blown. Power switch has continuity... don't feel like trying to 
debug and repair the "brick".


There are two Sony labels: One says Model RG1-1782 (I think that's the HP 
part number) and the other Model CD-91A, 100-115V.

Does anyone have a working one in their junkbox?

This is the LAST time I repair it before it goes to the recycler! I think 
I've changed every module except this one.
It has become my grandfather's axe: new head and new handle, but it's still 
my grandfather's axe :)


thanks
Charles 

Re: Looking for HP Laserjet IIp+ power supply

[Charles via cctalk]

Actually I just fixed it ;)  Never Mind.

I took the supply all the way apart and found one secondary filter cap that
had leaked electrolyte. Cleaned and fixed that, but still no luck. 155 volts
on the main filter cap. Then I noticed that occasionally it would try to
start for a blink but then the voltages would just drop to zero. So I
started looking around the section that had to be for bootstrap power to the
switching regulator, a common TL494 chip with datasheets online. Sure
enough, a small electrolytic on the primary side had blown its bottom out.
The diodes around it were still good. Changed that cap and a couple more
suspicious looking small ones and the voltages came right up (including the
24V once I pushed the cover-open microswitch).
Put it back in the printer, screwed it all together (a very modular design
for easier field servicing) and fired it up. Test page printed perfectly.
Saved some $ on a new laser printer. For now :)

I like these old cinder-block-sized (and weight) printers too. They last
ALMOST forever...

Charles 

H786 power supply help wanted

[Charles via cctalk]

I have a PDP-11/23+ and the power supply (H786) "last ran when parked" a 
year or so ago. But there's no DC output at all today, and the fans are 
running so there is AC power...
I also have the original H7861 that came with it, which had a blown chopper 
transistor. I couldn't find anything else bad, so I replaced the transistor 
and within a few seconds of running, it blew again. :(


So I need some help - I've never been good at fixing switching supplies, not 
to mention the high-side hazards.
The simplest solution would be just to replace it with a working unit. 
Anyone got one to sell, hopefully cheap? :)

If not, can anyone fix one or both of mine?

thanks!
Charles

Using PC power supply in BA-11S

[Charles via cctalk]

Regarding my earlier request for help repairing an H786 and H7861, it 
occurred to me that I could instead use a desktop PC power supply, having 
several in the junkbox.

It's even small enough to fit in there once the H786 is removed.

So I patched the wiring harness from the PC supply to the screw terminals on 
the backplane... 5 and 12 volts at the terminals, Fault lights on the RL's 
went out, but no green light on the KDF-11B.
After a look at the schematics, the simple solution was just to pull the 
power monitor daughter-card from the H786, so the power OK lines (8640 
buffer inputs, DC OK and Power OK) are not being pulled down. Green light 
on, memory test ran, and boots RT-11 from RL02 :) A better fix will be to 
drive the DCOK and POK lines from the PC supply, which appears to have a 
"P.G." orange wire (I'm betting "Power Good" but will check it out first).


TSX-Plus won't run though, because there's no real-time clock. Looks like a 
small transformer and a bit of buffer circuitry is needed to generate a 60 
Hz TTL pulse. Or a dongle with a 555 or crystal oscillator. I may have a try 
at fixing the original supply before going to the trouble (including 
mounting the PC supply in the chassis and jumpering the two ribbon cables 
together).


Speaking of trouble, today I learned that the "Restraining Cable Stud" 
mentioned in the 11/23 user manual is not just there for decoration. For the 
first time (ever), the BA-11S chassis overbalanced and fell out of the front 
of the cabinet. It hit the floor with a crash while yanking all the ribbon 
cables off (without breaking anything, incredibly, including a near miss to 
my feet in socks!)

Perhaps installing that cable is a good idea ;)

-Charles

Re: H786 power supply help wanted

[Charles via cctalk]

Update: I removed the H786 from the chassis, and set it up on the workbench 
with loads on the +5 and +12.
No output. 320V across the half-bridge, but no +12 Startup. Found I had 
forgotten to put a cliplead to the primary of the startup transformer.
Turned it on and it works... 5 and 12 volts into 1 ohm and 4.7 ohm 
respectively. WTF.

So I disconnected the PC supply, put the H786 back in, and it fired right up 
(including the real-time clock) and I ran it for half an hour.
Go figure. Ain’t classic computers fun sometimes...


From: Paul Anderson 
Sent: Saturday, March 30, 2019 3:26 PM
To: Charles ; General Discussion: On-Topic and Off-Topic Posts 
Subject: Re: H786 power supply help wanted


Hi Charles,

The H786 was standard for the 11/23, BA11-N. The H7861 was for the 11/23+, 
BA11-S and had afrw more amps of +5 volts.

I would start by looking at the electronic caps.

I have a few extras here but am pretty busy for the next week or so.

Paul

On Sat, Mar 30, 2019 at 2:25 PM Charles via cctalk  
wrote:

  I have a PDP-11/23+ and the power supply (H786) "last ran when parked" a 
  year or so ago. But there's no DC output at all today, and the fans are 
  running so there is AC power...
  I also have the original H7861 that came with it, which had a blown chopper 
  transistor. I couldn't find anything else bad, so I replaced the transistor 
  and within a few seconds of running, it blew again. :(

  So I need some help - I've never been good at fixing switching supplies, not 
  to mention the high-side hazards.
  The simplest solution would be just to replace it with a working unit. 
  Anyone got one to sell, hopefully cheap? :)
  If not, can anyone fix one or both of mine?

  thanks!
  Charles

Sticking RL02 positioner

[Charles via cctalk]

One of my RL02 drives (that sat for a long time) has developed what appears 
to be a sticky head positioner.
But it's only a problem going from the full-retracted position to loading 
track 0.

Once it's loaded, the drive will pass all seek and read/write tests.

It takes a surprising (to me) amount of force to pull the heads out into the 
disk area (power off, no pack). When they're out there, the arm slides back 
and forth easily.
Sometimes it won't load at all - push the load button, light goes out, disk 
spins up to what sounds like normal speed, but the heads never move and the 
Ready light doesn't come on.
There's supposed to be a Fault after 40 secs but that doesn't happen - it'll 
sit there forever spinning but not ready.
If I turn off the power and remove the pack, and pull the positioner out 
just enough to avoid opening the Heads Home microswitch (which causes a 
Fault light), then it'll spin up, load track 0, and work fine the rest of 
the day.


The manual (as usual) only recommends replacing the bad assembly for ease in 
field servicing, which is deliberate.
But I don't have a DEC repairman and a warehouse full of parts handy... Is 
there some kind of adjustment or lubrication I can do?
If I replace the positioner then I have to realign the heads (not too bad a 
job on this drive, though).

Any ideas?
thanks
Charles

Re: Sticking RL02 positioner

[Charles via cctalk]

-Original Message- 
From: Paul Koning

Sent: Monday, April 08, 2019 6:26 PM
To: Charles ; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Sticking RL02 positioner



On Apr 8, 2019, at 6:11 PM, Charles via cctalk  
wrote:


One of my RL02 drives (that sat for a long time) has developed what 
appears to be a sticky head positioner.
But it's only a problem going from the full-retracted position to loading 
track 0.

Once it's loaded, the drive will pass all seek and read/write tests.

It takes a surprising (to me) amount of force to pull the heads out into 
the disk area (power off, no pack). When they're out there, the arm slides 
back and forth easily.
Sometimes it won't load at all - push the load button, light goes out, 
disk spins up to what sounds like normal speed, but the heads never move 
and the Ready light doesn't come on.
There's supposed to be a Fault after 40 secs but that doesn't happen - 
it'll sit there forever spinning but not ready.
If I turn off the power and remove the pack, and pull the positioner out 
just enough to avoid opening the Heads Home microswitch (which causes a 
Fault light), then it'll spin up, load track 0, and work fine the rest of 
the day.


The manual (as usual) only recommends replacing the bad assembly for ease 
in field servicing, which is deliberate.
But I don't have a DEC repairman and a warehouse full of parts handy... Is 
there some kind of adjustment or lubrication I can do?


Lubrication in a disk assembly sounds like a thing to avoid because of 
contamination.


I don't know the RL02 specifically, but some pack type disk drives have a 
"head unload ramp", a wedge shaped device that lifts the heads away from the 
platters when the positioner retracts to the unload position.  I wonder if 
there might be dirt on those that could be cleaned with a suitable cleaner 
(kimwipes or similar lint free cleaner) and solvent (96% isopropanol comes 
to mind).  Does the book give any guidance about this sort of thing?


paul
===
Yes, I am sure there is such a ramp, since the heads do move close together 
when the positioner extends. I can feel it "wedging".
I'll take another look at it, when I have obtained some lint-free wipes or 
swabs :) 

Adding floppy drives to my PDP-11?

[Charles via cctalk]

I have a PDP-11/23+ with two RL02's in a corporate cabinet but no floppy 
drives. Also an RXV21 (M8029) card.


My PDP-8/A has RX01 drives, and I was hoping just to run the cable over to 
the -11 when I wanted to use floppies on it.
But after some searching, it appears that the RXV21 will only work with an 
RX02 drive...


Just wondering what my options are for hooking up any kind of floppy drives.
I could sell the RXV21 and buy/trade for an RXV11 (M7946) instead, to use 
with the RX01 in the other rack.
Or look for an RX02 that won't break the bank - but that won't fit in the 
corporate cabinet. I do have another cabinet but it's got other rack-mount 
gear in it at the moment.
What about smaller drives (RX50? RX33?)... can those be interfaced to the 
11/23+ Qbus?

Other thoughts?
thanks
Charles

FS: Qbus serial line cards

[Charles via cctalk]

I ran this ad back in 2015, will try again :)

I was going through my board collection and found three PDP-11 boards I've 
never used in years and don't see a foreseeable need.
No idea of condition, but they're visually clean and neat, stored in 
antistatic bags.


The serial cards came out of my working 11/23+ but I've not tested them 
(since I already have a 16-line card and only 2 terminals).


I have (one each):

M7957DZV11   Quad height 4-line serial card

M8053DMV11 "Microprogram Control" synchronous controller card (looks 
like it was intended for networking with 56k modems)


Dilog CQ1610 16-line serial card.

Make any reasonable offers. + shipping from US zip 65775.

thanks
Charles 

Dilog CQ1610 switch settings?

[Charles via cctalk]

I have a Dilog CQ-1610 serial line card (16 ports!) that I'd either like to 
sell, or at least put it in my backplane and play with it since I have a 
copy of TSX+

:)

But I can't find any info, especially the DIP switch settings. All I see is 
"emulates a Unibus DH-11" but that is not even close for hardware/layout.

Any thoughts?

thanks
Charles 

SIMH question

[Charles via cctalk]

This may be a silly question... but how can I transfer a text file from my 
PC into SIMH for PDP-11?
Is it even possible to create a disk or tape image from source code? 
Attaching files requires them to be images...


I have significant changes to make to TSGEN.MAC (TSX-Plus definitions file) 
and it will be MUCH easier to edit it on my laptop with a screen editor, 
than in SIMH (or on the real hardware) using the line editors!


The only method that comes to mind is to start the actual 11/23+, open the 
text editor for input, then use a terminal program like Teraterm to "play" 
the file as though I were typing it in.
But I don't have the rest of the TSX-Plus source files, linker, etc. so I 
would have to transfer them using VTserver anyway...

thoughts?

thanks
Charles

Re: SIMH question

[Charles via cctalk]

On 4/23/19 8:57 PM, Fritz Mueller via cctalk wrote:


On Apr 23, 2019, at 5:34 PM, Charles via cctalk classiccmp.org> wrote:


This may be a silly question... but how can I transfer a text file from 
my PC into SIMH for PDP-11?


I've found the most convenient way to do this, for a file or two at a 
time, is to use the paper tape reader/punch devices.  These can be 
attached directly to single files on the SIMH host, then the contents can 
be copied into or out of a simulated OS with PIP, cp, etc.




Two more options.

Get PUTR from dbit.com and use it to move the files onto an image
you can then mount  under SIMH.

Or, KERMIT.

bill
=
Thanks... unfortunately I'm running 64-bit Windows and just discovered PUTR 
will only run on a 32-bit (or even older) machine.
There was some interest in 2016 about an updated version but I can't find 
one.
I've got an ancient XP box upstairs that I use as a smart terminal for the 
PDP-8 (and PDP-11).

So now I get to have fun getting an XP machine to network with a Win7. Sigh.

VTserver problem (bug?)

[Charles via cctalk]

I sometimes use vtserver to download disk images to the RL02's on my 
PDP-11/23+.  Takes quite a while at 9600 baud, too :)


But there is some kind of bug that always appears at the same point, in the 
middle of the next 100K block after "6600K written".
The data transfer stops (no more head motion/ready light flicker on the 
RL02), and the character that vtserver uses to indicate a write operation 
just repeats endlessly and rapidly until I kill it.


Does anyone else encounter this limitation, and if so, how did you fix it? 
Fortunately I haven't wanted to image a disk that's more than 2/3 full so 
far... I make sure to squeeze the disk in SIMH before transferring the 
image. But it'd be nice to be able to image a full (10 MB) RL02 and not have 
to worry about it failing.


Any ideas?
thanks
Charles

Re:

[Charles via cctalk]

But there is some kind of bug that always appears at the same point, in the
middle of the next 100K block after "6600K written".
The data transfer stops (no more head motion/ready light flicker on the
RL02), and the character that vtserver uses to indicate a write operation
just repeats endlessly and rapidly until I kill it.


More information and a correction: I let it run on, and it is still reading 
and writing, but at a much slower and intermittent rate than the first 6.6 
MB.
The filler character is just a time marker of some kind, since I can still 
see the "r" indicating a read from the .dsk image, and the light on the RL02 
flickers after a few of those.

So it's slowed way down, but not stopped! Even more mysterious.

Anyway, this disk has 13800 blocks out of 20800 used. If RT-11 stores data 
(including the directory structure) starting from block 0, I may be able to 
kill the writes after 7 MB.
(Unfortunately I think I neglected to squeeze the image before sending it to 
the RL - and naturally the important TSX files are near the end - which 
means I have to wait for most of it).
If I have to do it again, I'll squeeze and then kill it after 7 MB and see 
what I got!

Re: VTserver problem (bug?)

[Charles via cctalk]

-Original Message- 

But there is some kind of bug that always appears at the same point, in the
middle of the next 100K block after "6600K written".
The data transfer stops (no more head motion/ready light flicker on the
RL02), and the character that vtserver uses to indicate a write operation
just repeats endlessly and rapidly until I kill it.


More information and a correction: I let it run on, and it is still reading
and writing, but at a much slower and intermittent rate than the first 6.6
MB.
The filler character is just a time marker of some kind, since I can still
see the "r" indicating a read from the .dsk image, and the light on the RL02
flickers after a few of those.
So it's slowed way down, but not stopped! Even more mysterious.

Anyway, this disk has 13800 blocks out of 20800 used. If RT-11 stores data
(including the directory structure) starting from block 0, I may be able to
kill the writes after 7 MB.
(Unfortunately I think I neglected to squeeze the image before sending it to
the RL - and naturally the important TSX files are near the end - which
means I have to wait for most of it).
If I have to do it again, I'll squeeze and then kill it after 7 MB and see
what I got! 

Re: VTserver problem (bug?)

[Charles via cctalk]

And even more bizarrely... it crawled its way up to the 7400K block, and now 
it's going at normal speed again! 10MB should be done soon.
I have no idea what could be causing this major slowdown from 6.6-7.4 MB. 
It's not the drive because two different ones do the same thing (and they 
work perfectly otherwise)...


Hopefully I won't have to go through the (edit, reassemble, relink, PUTR 
transfer to an image, vtserver to the disk) loop too many times, attempting 
to get my DHV11/16D to function with TSX+ 6.50... I had somehow inserted a 
couple of characters that didn't belong there while editing (bumped the 
keyboard maybe?) so I'm on the second pass.
Also I found what looks like a typo in the TSGEN.MAC file if anyone's 
interested.

TSX-Plus help needed!

[Charles via cctalk]

OK, I have figured out how to modify TSGEN.MAC, use PUTR to make a disk 
image, load it in SIMH, reassemble, relink, and *finally* send it to an RL02 
pack via vtserver!

TIme-consuming but doable. I've been wrestling with this all day.

BUT - TSX+ 6.50 just will not run. At all.
Using RT-11SJ (5.01), after typing "R TSX" I can hear the disc access for a 
few seconds, a pause, a few more accesses... then nothing. It just hangs. 
Nothing on the console either., no response to .


When starting it in SIMH (the same disk image), I get the error message 
?TSX-F-Computer line clock is not working. Figured that was just a SIMH 
thing.
But the address/vector is correct in TSGEN.MAC... and when checking TIME in 
RT-11, the seconds advance in real-time like it should.


On the real hardware, the error message doesn't display, and the clock is 
running...


My old version of TSX+ is 6.16 and it runs fine on console and SLU 2, just 
needs rebuilt to use different serial cards than the original system.

So where should I start looking first? RT-11 version incompatibility?
Any TSX+ experts online? Thanks for any help. This is driving me nuts!

Looking for Silent 700 printhead

[Charles via cctalk]

I have two Silent 700 terminals (model 745) that I bought quite a few years 
ago (nonworking). Couldn't find a schematic. Last week I just happened to 
search for one - and found a complete service manual with theory of 
operation and full schematics! So I got them on the workbench.


The more worn one wouldn't print anything on the paper but was otherwise 
working. I found that the nylon printhead pressure adjustment wheel had 
split and fallen off the solenoid shaft into the case, along with the 
pressure spring. Then it would print, but I promptly discovered that the 
printhead has several "dots" missing in a pattern that could not be 
accounted for by the driver circuitry. I confirmed it by swapping the 
printhead from the other one, and now it prints perfectly. So at least I 
have one working now :)


The second one in half-duplex mode will only beep (Ctrl-G), CR and LF in 
half-duplex mode, so I know the keyboard is alive and there is power.
But it otherwise won't move the carriage forwards (including space), or 
print any characters at all.


Before I go to the trouble of diagnosis and repair, does anyone have a good 
printhead, or know where I can find one?
No point in fixing it if the characters won't be printing properly when I'm 
done...


thanks
Charles

RT-11 doesn't recognize my 3.5" floppy

[Charles via cctalk]

I have installed an RQDX3 and the M9058 distribution board in my 11/23+. 
Since I don't have a 5.25" drive yet, I hooked up a 3.5" HD (1.44 MB) drive 
from an old PC.
After a struggle (which I documented on VCFED's DEC forum), I managed to get 
all the jumpers and cables set correctly, and now my XXDP diagnostics 
(ZRQA?? ... ZRQF??) recognize the drive as an RX33 (DU0:, logical drive 0 
since no hard disks are attached). It passes all the tests, and I can INIT, 
DIR, and copy files to it using the limited OS with the XXDP suite. The LED 
on the RQDX3 blinks once when the drive is accessed. So far so good.


But, when I boot the system (with RT-11SJ V5.01), it can't see the drive at 
all. Attempts to access it result in the command hanging indefinitely, the 
drive does not select, and the RQDX3 lamp flashes rapidly. SHOW DEV:DU does 
say that the handler is installed for the correct 172150, 154 location. 
However, SHOW DEV:DUn where n=[0..3] displays two blank lines then back to 
the dot prompt.


Is my version of RT-11 just too old to recognize an RX-33? If so, what do I 
need to fix this? Presumably a later DU.SYS?
Thanks for any help. Most of my experience is with PDP-8's so this is slow 
going...

-Charles

Re: RT-11 doesn't recognize my 3.5" floppy

[Charles via cctalk]

Thanks... I have an RT-11XM pack with version 5.04, booted the system from 
that - and it does recognize the floppy!
Except that whoever built it didn't bother to include DU.SYS, just DUX.SYS. 
Grrr.


Now I just have to figure out how to update the old RT11SJ 5.01 that my TSX+ 
runs on top of, to a later version, without clobbering all my work building 
it :)

Guess I get to learn how to make an RT-11 bootable disk!



-Original Message- 
From: John Forecast

Sent: Monday, May 06, 2019 5:38 PM
To: Charles ; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: RT-11 doesn't recognize my 3.5" floppy

The release notes on bitsavers indicate that the RX33 was not supported 
until RT-11 V5.04.


 John.

On May 6, 2019, at 6:20 PM, Charles via cctalk  
wrote:


I have installed an RQDX3 and the M9058 distribution board in my 11/23+. 
Since I don't have a 5.25" drive yet, I hooked up a 3.5" HD (1.44 MB) 
drive from an old PC.
After a struggle (which I documented on VCFED's DEC forum), I managed to 
get all the jumpers and cables set correctly, and now my XXDP diagnostics 
(ZRQA?? ... ZRQF??) recognize the drive as an RX33 (DU0:, logical drive 0 
since no hard disks are attached). It passes all the tests, and I can 
INIT, DIR, and copy files to it using the limited OS with the XXDP suite. 
The LED on the RQDX3 blinks once when the drive is accessed. So far so 
good.


But, when I boot the system (with RT-11SJ V5.01), it can't see the drive 
at all. Attempts to access it result in the command hanging indefinitely, 
the drive does not select, and the RQDX3 lamp flashes rapidly. SHOW DEV:DU 
does say that the handler is installed for the correct 172150, 154 
location. However, SHOW DEV:DUn where n=[0..3] displays two blank lines 
then back to the dot prompt.


Is my version of RT-11 just too old to recognize an RX-33? If so, what do 
I need to fix this? Presumably a later DU.SYS?
Thanks for any help. Most of my experience is with PDP-8's so this is slow 
going...

-Charles

Re: RT-11 doesn't recognize my 3.5" floppy

[Charles via cctalk]

On 05/07/2019 11:15 AM, Douglas Taylor via cctalk wrote:

Very interesting , now that you got it to work, what can you use it for?
Will it be an exchange media with PUTR?

Doug

On 5/6/2019 6:20 PM, Charles via cctalk wrote:

I have installed an RQDX3 and the M9058 distribution board in my
11/23+. Since I don't have a 5.25" drive yet, I hooked up a 3.5" HD
(1.44 MB) drive from an old PC.
After a struggle (which I documented on VCFED's DEC forum), I managed
to get all the jumpers and cables set correctly, and now my XXDP
diagnostics (ZRQA?? ... ZRQF??) recognize the drive as an RX33 (DU0:,
logical drive 0 since no hard disks are attached). It passes all the
tests, and I can INIT, DIR, and copy files to it using the limited OS
with the XXDP suite. The LED on the RQDX3 blinks once when the drive
is accessed. So far so good.


Did you actually test the drive by formatting, reading and writing?


But, when I boot the system (with RT-11SJ V5.01), it can't see the
drive at all. Attempts to access it result in the command hanging
indefinitely, the drive does not select, and the RQDX3 lamp flashes
rapidly. SHOW DEV:DU does say that the handler is installed for the
correct 172150, 154 location. However, SHOW DEV:DUn where n=[0..3]
displays two blank lines then back to the dot prompt.

Is my version of RT-11 just too old to recognize an RX-33? If so,
what do I need to fix this? Presumably a later DU.SYS?
Thanks for any help. Most of my experience is with PDP-8's so this is
slow going...
-Charles





RT11V5 works for me using RQDX3 and the distribution board in the BA23
box assembled as a MicroPDP-11 with RX33
and RD52 (Quantum 31mb).  Never thought much about it other than to make
sure the RX33 was jumpers were correct
and making a dummy panel for the smaller than RX50 drive.

The 11/73 system has the RQDX3 and the signal distribution board (m8058)
out of BA123 to hook up
RD52, RX33, RX23 and never had issues due to addressing devices under RT11.

Is it possible you have a interrupt grant gap between the various boards
and the RQDX?  That would cause a hang.

If you successful it makes using PUTR easier though RX50 works for that
too just smaller.
===
Not a hardware or installation problem (once I got everything hooked up 
right, that is)...


As another member helpfully pointed out, 5.04 is the first version of RT11 
that supports RX33. I have 5.01 on my TSX+ RL02 pack.
Once I booted with an RT11XM 5.04 disk, I can format, read and write the 
floppy :)


Now I have to figure out how to upgrade to RT11SJ 5.04 or later without 
bombing the contents of the RL02. Remaking a pack with VTserver is a pain.


Yes, the plan is to use PUTR on an old Windows box that I use with my PDP's.

I'll probably use Front Panel Express to make a nice rack panel for a 3.5" 
and a 5.25" drive, instead of having the bare drive sit on top of the RL02 
in the corporate cabinet ;)

Re: RT-11 doesn't recognize my 3.5" floppy

[Charles via cctalk]

On 06/05/2019 23:38, John Forecast via cctalk wrote:
The release notes on bitsavers indicate that the RX33 was not supported 
until RT-11 V5.04.


On May 6, 2019, at 6:20 PM, Charles via cctalk  
wrote:


I have installed an RQDX3


But, when I boot the system (with RT-11SJ V5.01), it can't see the drive 
at all.


Not only was the RX33 not supported until 5.04, there's a bug in the
MSCP DU driver that wasn't fixed until 5.03 (IIRC) or maybe 5.04, which
means nothing on an RQDX3 can be guaranteed to work properly before
that.  It caused me a lot of grief, way back in 1994.

See the files at http://www.dunnington.info/public/RQDX/ and
particularly http://www.dunnington.info/public/RQDX/DUX.TXT if you're
interested.

--
Pete
Pete Turnbull
=
thanks for the additional info. Will check out the links.

Meanwhile, I found an RK05 image of RT-11 "5.4" on bitsavers, made an RL02 
bootable -SJ image on SIMH, then copied it over to the hardware with 
VTserver.
(I didn't have to wait for the entire 10 MB since the contents were all on 
the first 3 MB anyway and no bad blocks).
The system booted up to a 5.04 prompt and DU0: is fully usable with 2382 
blocks on a 3.5" diskette :)


My TSX+ 6.50 copy also didn't have DU enabled in TSGEN.MAC so I had to 
uncomment that DEVDEF line and reassemble/relink. It's SLOW on my 11/23+... 
we're spoiled with GHz PC's and GB of RAM.

Now I can use the floppy under TSX+ too.

But the generic 3.5" drive in my WinXP box can't successfully emulate an 
3.5" RX33 with PUTR, apparently. (Nor an RX23).
I only get read/write/directory errors after several seconds of head 
activity even with /RX33 and /RT11 switches set.

Time for more reading and maybe drive swapping/tweaking...

Bug in PUTR?

[Charles via cctalk]

I'm having trouble copying files from my PDP-11 (RT-11 format) into an old 
Windows box using the last version of PUTR.
It appears that WinXP does strange things with the hardware (3.5" 1.44 MB 
drives aren't actually RX33's although my RQDX3 controller believes they 
are).
So I made an MS-DOS boot disk and run PUTR directly on MS-DOS (instead of 
the WinXP DOS window). Unfortunately MS-DOS 6.22 can't recognize my hard 
drive since it's NTFS-formatted, so it all has to be done in floppies.


Both WinXP and MS-DOS know that A: and B: are two separate drives. Likewise 
the BIOS settings. I can copy files in DOS and Windows back and forth 
between the two drives.
And I can MOUNT B: as a logical device DU0: (or without a logical device 
name, as B: /RX33 /RT11), and read its directory.
But when I try to copy a file from A: to DU0:, the B: drive light flashes 
briefly, and then PUTR tries to write over the A: drive (blocked by the 
write- protect tab once I wised up)!


So how on earth can the BIOS, MS-DOS and WinXP all know that A: and B: are 
two separate drives, but PUTR tries to write to A: even though the command 
is to write B: ??


I also tried switching the PUTR disk into B: and the RT-11 formatted disk to 
drive A:. Same problem (tries to write over the source disk which is now B: 
even though the output filespec is clearly A). I had a look at the code but 
nothing's leaping out at me. Although it's been many years since I wrote any 
8086 code...

Re: Possible PUTR bug?

[Charles via cctalk]

John Wilson confirmed that his program was designed to work with one floppy 
and an HDD. He says strange things happen if one tries to use two floppy 
drives instead... just as I found ;)
I removed the second floppy drive, dug out an old 540 MB hard drive (with 
Win 95 on it) and hooked it up to the PC. Started Win95, then "Restart the

computer in MS-DOS mode", copied PUTR to the C: drive and started it.

PUTR now works perfectly, transferring files in both directions to an the 
emulated RX33 (3.5" floppy). The PDP-11 can read and write those disks on

its generic 3.5" floppy "RX33", too. :)

Now I just have to figure out the PC partitions/hard drives to make using 
PUTR as simple as possible.

Re: Possible PUTR bug?

[Charles via cctalk]

Just an update... I spent an entire long afternoon wrestling with that old 
PC, trying to find some combination of HDD jumpers and BIOS settings that 
would allow the XP hard drive to boot with another drive attached (either on 
the slave connector or the secondary channel with the CD-ROM removed). No 
dice.


So I had the bright idea to use Minitool's Partition Wizard, and shrink my 
Windows partition so there'd be room for a  newDOS partition.
But it won't even run (probably because I have only 64 MB RAM on that box). 
Grrr. It's unbelievably slow anyhow, so more SDRAM on order, which is really 
cheap these days.
I'd get a newer PC for the workbench, but need to keep the old motherboard 
because there are a couple of devices (including a PB-10 PROM programmer) 
which are ISA slots.


So, this has become a Windows/PC (ugh) project instead of just being able to 
play with my PDP-11...

Network cards and Win98SE

[Charles via cctalk]

I have tried for two days to get wireless networking running on my old PC 
under Win 98SE, so I can use PUTR without a separate partition or boot. XP 
is on an 8.4 GB drive. 98SE is on an older 540 MB drive.


There are two network cards (a Netgear WPN311 with Atheros chipset, and an 
Encore ENWLI-G2 with Realtek 8185 chip) and neither will work with Win98SE.
I have tried the manufacturer's drivers, Atheros drivers, Realtek drivers... 
none of it works. The Realtek driver installs but gives a fault in RUNDLL32.


Netgear's website claims that the WPN311 can run under 98SE and later.  Some 
sources for that driver package say it starts with XP. Although I would tend 
to believe the manufacturer...
The same Netgear card in the same motherboard was working correctly with the 
XP drive.


I even did a fresh install of 98SE. Then installed the WPN311 software, then 
the card. Windows says the card is installed and working properly.
But the Netgear utility won't run (hangs, Task Manager showing wlancfg5 not 
responding). That's usually because it can't see the card.


Searching the net including various forums from years ago hasn't helped.
So I'm about to give up. Wasted enough hours on this. Back to XP with a DOS 
partition for running PUTR.

Unless someone has a better idea :)

thanks
Charles

Re: Network cards and Win98SE

[Charles via cctalk]

Thanks for the tips. The reason I’m not using Ethernet cable is because the 
Vintage Computer Room (where this PC resides) is on the 2nd floor around a 
couple of corners, and my DSL modem/router and unfiltered phone line are in 
the 1st floor study. Would take a long run and some drilling, or duct taping 
it to the banister and hoping the dog and cats don’t eat it ;)


However, after finally giving up on the wireless cards... I realized that I 
had a simple Linksys LNE100TX Ethernet card in the PC junk pile. I installed 
that (it was recognized by 98SE and the drivers worked first time too), then 
brought my laptop upstairs and set it up as a bridge. That works, but is 
clumsy and requires another computer.


My next idea was to find a wireless device to connect to the Ethernet card. 
I found out about WLAN, bridging, and most importantly, that many models of 
router can be reflashed with dd-wrt software, and act as the bridge I 
needed! Also in the closet was a Linksys E1200 router, which is one of the 
models supported by dd-wrt. So I flashed it and hooked it up.


After a bit of struggle (incomplete directions but I managed to fill in the 
missing pieces) I now have wireless network and Internet access on the old 
machine :)
Incidentally, PUTR now works perfectly since I’m running 98SE/DOS. 

Re: Network cards and Win98SE

[Charles via cctalk]

You could have installed a gaming adapter, opened the web page,
connected it to the wireless and been done.


Sure, but you assume I know anything about online gaming (I don't); it would 
require purchasing one, *and* I already had the Linksys router and card, 
just gathering dust for years!
I like to improvise with what's on hand rather than spending money on a 
really ancient PC :) 

Looking for my old ADM-3A

[Charles via cctalk]

I used to have an ADM-3A Dumb Terminal... fixed it up, and made my own 
lower-case ROM from a 2716 EPROM and a lot of small wires.

Sold it around 2005 or so, but can't remember who bought it.

Anyway I'd like to buy it back if the current owner is out there and isn't 
using it :)

Thanks
Charles 



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ADM-3A question

[Charles via cctalk]

I bought an ADM-3A on ebay. The monitor and the circuit board/keyboard are 
from two different terminals - confirmed by hand-engraved serial numbers on 
the halves that don't match.

Not to mention the two different case colors (pale blue top, blue bottom)!
But it does have the lower-case option already installed :)

Anyhow, there appears to be some breakdown of the CRT implosion plate 
silicone (screen rot). I've read about this problem before, so no real 
surprise
It seems to be turning into brown "goop" which has run down onto the circuit 
board.
Do I need to remove the goop before powering it up? Or is it nonconductive 
and hopefully noncorrosive, so it can wait until I remove the implosion 
plate and fix it?


thanks
Charles


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Re: ADM-3A question

[Charles via cctalk]

I decided just to fire it up and see if anything blew... it issued the 
expected beep as it came up.
Set the switch to half-duplex and it does actually echo bell (Ctrl-G) and I 
can see the screen moving as I type!
But there  is some kind of garbage every other row, although the cursor 
moves and the screen will "clear" (except for the 12 rows of garbage).

Power supply is 5.11 volts. So far so good.

Unfortunately the screen rot is even worse than I thought - the PVA layer is 
so opaque and bubbled it looked like cottage cheese once removed, and I 
can't make out what characters are on the CRT... I took the monitor out 
(very easy disassembly). I didn't even have to use a heat gun or a hot wire, 
just started at one corner, applied a steady and gentle pull, and it came 
off in one sheet with a giant sucking sound.


That oily mess took a while to clean up. I also scrubbed off the black 
anti-reflective coating since it was significantly scratched and peeled 
anyway.
Now waiting for the bead of clear silicone (around the outside of the plate 
only) to cure. I'll make sure it's air tight so no black dust will get in 
there by electrostatic attraction.


I can fix the RAM problem once I can see what is actually on the screen! ;)
Also the wire bracket with threaded ends that holds the flyback to the 
monitor chassis is missing one end entirely, so I need to fix that (keep the 
core halves firmly together).
Looks like I didn't get TOO bad a deal for $200 shipped, especially with 
upper-case installed. 



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Re: ADM-3A question

[Charles via cctalk]

On 8/10/19 8:33 AM, Charles via cctalk wrote:

I also scrubbed off the black anti-reflective coating since it was
significantly scratched and peeled anyway.


um.. you didn't remove the aquadag from the outside of the crt, did you?


No worries Al, I got my EE in '81 back when CRTs were still in use and I 
know how they work ;)


I was referring to the translucent stuff on the (removable) glass implosion 
plate itself, designed to reduce light reflection, not the 'dag.
Some say that black sheer pantyhose can be used to recreate the same effect, 
or a 3M Privacy Screen. 



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Test

[Charles via cctalk]

Testing 1,2,3... my last couple of posts don't seem to be showing up?
-Charles


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Re: ADM-3A question

[Charles via cctalk]

Thanks Bill, I hadn’t seen that particular page. As I mentioned already, the 
formerly clear “stuff” was so deteriorated I could just pull the glass plate 
off with gentle fingertip pressure.
I ran a bead of clear silicone around the outside of the clean plate and CRT 
face and bonded them back together.

Display looks great!

However, I can now see that every other line, starting with line 2, is 
showing a full line of double quotes (0x22) instead of spaces (0x20). I read 
the circuit description and schematic, and it appears that bit “2” is stuck 
high on the even-line RAM – for some reason the designer decided to call the 
LSB bit 1 instead of bit 0.


Typing (for example) “abcdef123” shows the correct text on the blank odd 
lines, but on the even lines it echoes as “cbcfef323”. Confirming that stuck 
bit.
Looks like the RAM at location H15 should be the bad one... we’re having a 
heat wave and it’s too hot upstairs to work on it until tomorrow morning at 
the earliest.


ETA: Now it's tomorrow morning and just cool enough (although 100% humidity, 
at least outside) but my replies aren't showing up in the archive - filtered 
somehow.


Anyway. I did a bit more Googling and discovered that plain water dissolves 
the PVA goop just fine. No need to use a lot of expensive alcohol which 
seems to be a less effective solvent anyway!
So I took the board out and scrubbed it in the kitchen sink with running 
warm water and an old toothbrush. Rinse with distilled water, now gently 
baking in the oven at around 140F to get the water out of the keyboard. Then 
onto the RAM replacement.



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Re: ADM-3A question

[Charles via cctalk]

After replacing the RAM, the display is now back to normal (there's also a 
test switch on the motherboard (S6) that switches the display from blank 
spaces to all zeroes.
The one that failed was a National Semi 2102, whereas the others are all 
from another manufacturer. No sign of previous replacement. Interesting.
(I once fixed up a PDP-8/L, chased down several bad chips. Nearly all were 
Signetics 7440's).


I may have made a tactical error though - turns out that wet/damp PVA is 
electrically conductive! Enough to overcome the 5k pullup resistors. An 
unpleasant surprise. So now the keyboard thinks multiple keys are being 
pressed and won't work at all. Removing the keyboard to clean underneath it 
would be very tedious since every key has two soldered pins...


There was a significant buildup of goop underneath the key scan mux and 
demux chips where the pins are close together (0.1"). I gave the bottom half 
of the board another good
rinse and will let it dry overnight, maybe a hair dryer too. Or get some 
more 91% alcohol to it and a longer low-temp bake. It all worked before my 
"cleanup" so I expect it will resume normal operation once the moisture is 
out of any remaining goop. I hope ;)




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Re: ADM-3A question

[Charles via cctalk]

After hanging vertically for 36 hrs in a hot upstairs room, more goop seeped 
out from under the keyboard. It now works again. Whew.


While running on the bench for burn-in testing, a cursor problem suddenly 
appeared... it would only move every other keystroke. With the technical 
description and schematic at hand, it wasn't hard to track down a 74LS193 
up/down counter with a blown (floating) LSB output. Confirmed by manually 
toggling that bit and the cursor would move back and forth one position. 
Meanwhile I removed the bad chip and put in a DIP socket. Naturally my TTL 
collection didn't have an 'LS193 so I'm waiting on that. So I have a 24 
line, 1 column terminal :)


The monitor was occasionally intermittent (no display at all, no HV, +15 and 
drive signals OK). It seemed to change with movement of the wiring harness 
from the main board to the monitor, too. I reseated the edge connector on 
its PCB and it seemed to be fixed - but then the VERTICAL deflection 
collapsed and tweaking the height adjustment caused increasing loss. The 100 
ohm pot to the base of the vertical output transistor had picked that moment 
to go open. Changed that out and readjusted everything - so far so good 
after another hour of run time.


This ADM-3A could have been unpowered (and in a storage area without climate 
control) for a very long time. I wonder if that contributed to the failures 
I'm seeing... hope there aren't any more until I get to use it for a while 
on my PDP-8/A (or 11/23+). 



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Re: ADM-3A question

[Charles via cctalk]

Thanks. I believe you are right also :)
The expensive ceramic packages have hermetic seals, not so the plastic
(epoxy) packages used in commercial grade parts.

There are some kind of failures that can be fixed by baking - but I don't
know if this is one of them (if the bond wire is soldered to the die it
might work). If it detached from the weld at the lead frame, no go. Anyway
there are over 100 chips on the ADM-3A board and I would be more worried
about damaging the others with heat.
I just paid 71 cents for another LS193 ;)

Charles
WB3JOK/0

-Original Message- 
From: Dave Wade

Sent: Wednesday, August 14, 2019 5:02 AM
To: 'Charles' ; 'General Discussion: On-Topic and Off-Topic Posts'
Subject: RE: ADM-3A question

Charles,

I believe that TTL chips suffer from failure or detachment of the bonding
wire that runs from the die to the interconnect pin, which would result in a
floating pin as described.]
Not sure if environmental storage affects this as chips should be sealed...

I have also recently seen it suggested that heating the chip up in an oven
could affect a temporary repair (sorry I can't find the reference now).

Dave
G4UGM


-Original Message-----
From: cctalk  On Behalf Of Charles via

cctalk

Sent: 14 August 2019 00:20
To: cctalk digest 
Subject: Re: ADM-3A question

After hanging vertically for 36 hrs in a hot upstairs room, more goop

seeped

out from under the keyboard. It now works again. Whew.

While running on the bench for burn-in testing, a cursor problem suddenly
appeared... it would only move every other keystroke. With the technical
description and schematic at hand, it wasn't hard to track down a 74LS193
up/down counter with a blown (floating) LSB output. Confirmed by manually
toggling that bit and the cursor would move back and forth one position.
Meanwhile I removed the bad chip and put in a DIP socket. Naturally my TTL
collection didn't have an 'LS193 so I'm waiting on that. So I have a 24

line, 1

column terminal :)

The monitor was occasionally intermittent (no display at all, no HV, +15

and

drive signals OK). It seemed to change with movement of the wiring harness
from the main board to the monitor, too. I reseated the edge connector on

its

PCB and it seemed to be fixed - but then the VERTICAL deflection collapsed

and

tweaking the height adjustment caused increasing loss. The 100 ohm pot to

the

base of the vertical output transistor had picked that moment to go open.
Changed that out and readjusted everything - so far so good after another

hour

of run time.

This ADM-3A could have been unpowered (and in a storage area without
climate
control) for a very long time. I wonder if that contributed to the

failures I'm

seeing... hope there aren't any more until I get to use it for a while on

my PDP-

8/A (or 11/23+).


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Re: ADM-3A question

[Charles via cctalk]

Today the replacement 'LS193 arrived, so I put it in the 
previously-installed socket and the screen is now 24x80 again :)
I'd been testing with the dip switch in half-duplex mode... For final test, 
I put it in FDX, connected to my HP protocol analyzer, and what do you know, 
no serial data out.
The 1488 RS-232 driver was blown (TTL-level data going to it, but the RS-232 
line was stuck in spacing). Not an uncommon failure with static discharge 
and incorrect cable hookups...
I destructively removed it, again installed a good dip socket, now waiting 
for THAT chip (a variety of other line drivers in my drawer, but not 
1488/1489).


Meanwhile I noted another slide switch S8 ("GT/LK") near the DB-25 
connectors. It is not referenced anywhere in the documentation, nor in the 
schematics!
The wiper of the switch also goes through a hex inverter to a 74LS32 chip, 
ALSO not in the schematic or circuit description. This signal originates at 
the flip-flop that generates KBLOCK\.
Finally, input pin 10 of the removed 1488 is supposed to be tied to pin 9, 
with the RTS output on pin 8. But pin 10 goes In fact, the PCB artwork at 
the end of the tech manual shows no connections except +5 and ground to that 
chip (position C2 I think), and it doesn't show the slide switch either.


This is likely something for the auto-tester that LSI used to check these 
boards on the production line, although I don't know if the extra circuitry 
was added or removed during production.
Anyone have internal documents on this? I'm just curious since it only 
appears to affect the keyboard lock functions which I'm not using anyway.



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Re: ADM-3A question

[Charles via cctalk]

I found a newer version of the tech manual on bitsavers, which does mention 
the mysterious S8 switch (as well as the S6 switch that fills the screen 
with 0's upon clearing).


"The gated EXTENSION port mode, when selected
by switch S8, allows selective transmission of
data from the keyboard, in Half-Duplex mode, or
the communication line through the
EXTENSION port.

GT: Enables gated EXTENSION port
mode which allows ON/OFF control of
the EXTENSION port.

LK: Disables gated EXTENSION port mode
which allows locking and unlocking off [sic]
keyboard."

The wiring is on the newer schematic, too. Another of life's little 
mysteries, solved :)



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Re: ADM-3A question

[Charles via cctalk]

I am still struggling with my ADM-5.  The smoke I mentioned last time came

from a tantalum capacitor decoupling a -20V supply.  After removing it, I
got back to the monitor showing a cursor.

Interesting you should mention that... early in the debugging process 
(always start with the power supplies!),
I had discovered the +12/-12 power supplies weren't right. (+12 was very 
low). The problem was a fractured solder joint on the PCB's male Molex 
connector

J3. Specifically, pin 4 (red/white) - the center tap of the transformer.

This is the worst pin to be open since the load on the +12 is much greater 
than the -12, so the voltage across the unregulated supply soared on the
minus side to over 35 volts (should be + and - 20v, as you mentioned). The 
electrolytic is rated at 35 volts, and of even more concern, so is the 2.2 
uf tantalum bypass. Those match-head tantalum caps are known for 
short-circuiting even when operated below their maximum rated voltage (as 
any Tek owner can attest).
Fortunately I found the problem before the tantalum exploded and took out 
the bridge rectifier with it. 



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Pinout for current loop interface

[Charles via cctalk]

Is there any standard pinout for 20 ma current loop using a DB-25 connector, 
analogous to the well-documents RS-232 serial interface?


My PDP-8/A drives an ASR-33, and having just restored an ADM-3A I want to be 
able to unplug the TTY and plug in the ADM.
I somewhat arbitrarily put the transmit data + on pin 2 and receive + on pin 
3, and picked two uncommitted RS-232 pins for the - legs of both loops.


The ADM-3A receives on pins 23 & 25, and transmits on pins 24 & 17. Polarity 
doesn't matter since both pairs use bridge rectifiers.
If this is some kind of de facto standard, I'll change the bulkhead 
connector on the PDP-8 and the TTY to match.
Otherwise I'll just make yet another unique cable to hook up the ADM-3A to 
the PDP-8 as it's wired.


Or would you recommend I use a different connector entirely? The reason I 
used the DB-25 to begin with is that I had a DEC rack-mount plate that 
already takes one.

Maybe a Jones 4-pin would make more sense.

thanks for any tips.
-Charles


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Re: Pinout for current loop interface

[Charles via cctalk]

I've never heard of people using DB25 for 20mA, at least historically,

contemporaneous with its widespread actual use. E.g. DEC universally used
'flat' 8-pin Mate-n-Lok connectors for 20mA serial connections.

Thanks for the comments... I asked mostly because the ADM-3A has both RS-232
and current loop interfaces built-in (on the same female DB-25), selected by 
one of the

DIP switches.

I just hate having to make a custom cable for every terminal and computer I
own or work with ;)

-Charles


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Re: Pinout for current loop interface

[Charles via cctalk]

In my prior life as an EE, I had to do it many times (early 80's)... I may 
be nostalgic, but not THAT nostalgic :)



-Original Message- 
From: Chris Hanson

Sent: Saturday, August 17, 2019 1:37 PM
To: Charles ; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Pinout for current loop interface

On Aug 17, 2019, at 9:14 AM, Charles via cctalk  
wrote:


I just hate having to make a custom cable for every terminal and computer 
I

own or work with ;)


Ah, but isn’t doing what so many before you have had to part of the charm? 
:)


 -- Chris 



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Re: ADM-3A question

[Charles via cctalk]

Tried the ADM-3A out today on my PDP-8/A via the 20 ma current loop 
interface - just unplugged the ASR-33 and plugged in the glass TTY :)
Worked great (the current loop probably had never been used, so no one had a 
chance to blow it up), but I got tired of holding down the Shift key since 
OS/8 doesn't understand lower case letters.
So I decided to set its switch to upper case only... terminal kept putting 
out lower case.


Sure enough, that switch contact was stuck closed. It'd probably never been 
moved since the terminal was new!
Now waiting on a 6-position dip switch from Mouser. And some 8-position 
Mate-n-Lok connectors.



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Re: ADM-3A question

[Charles via cctalk]

Today I got home and my Mouser order had arrived. I soldered in the new 
6-position DIP switch and popped a new 1488 in the socket. Nice RS232 data 
coming out... for about 10 seconds, then the transmit data line went to 
around +2 volts and stayed there. WTF. Tried another one, same thing. Went 
back to the first new chip, same thing - so it's not blown (and maybe the 
old one wasn't either).


OK, it has to be the power supplies. Again.
Sure enough, +12 was sinking slowly until it was near zero at which point 
the RS232 output basically went floating...


This looked familiar and it didn't take long to discover that the CT on the 
transformer for the + and - 12 volt supplies was open again!! This time it 
was the wire from the transformer broken as it entered the Molex connector. 
Fixed that, back in business. I am amazed that none of the epoxy drop 
tantalums on the high leg with the open neutral have blown. Maybe they're 
open circuit :)


Also I don't know what gorilla at the salvage place was 
connecting/disconnecting until he found a combo of base, board and monitor 
that worked. 



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Re: Test message

[Charles via cctalk]

Sorry, we did not receive your message. Have you tried turning it off and 
back on again?
:) 



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Connecting SIMH to teletype via USB

[Charles via cctalk]

I could use a hint... I have a USB to current-loop (Volpe) interface board, 
and Windows 7 on my laptop does recognize it as COM4 at 110 baud.

So far so good. No problem hooking it up to my ASR-33 Teletype.

Now I'd really like to figure out how to set SIMH to use the 33 as the 
console, so the TTY will be attached to the virtual PDP-8.
I do have OS/8 and TSS/8 running on SIMH with the laptop as console. Just 
don't know how to make it "talk" to the USB serial port instead.
Anything that starts with "set console..." gives a "no settable parameters" 
error.


Thanks for any hints.
-Charles


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Re: Connecting SIMH to teletype via USB

[Charles via cctalk]

I'm using a slightly older SIMH and user's guide (3.8 something). This SIMH 
will not allow Set Console Serial, apparently (No settable parameter
I only found the suggestion for Telnet in my user guide, so I did Set 
Console Telnet:23. It does accept that.


So now I was just trying to use Tera Term which defaults to port 23... Is it 
even possible to run Tera Term in one window and SIMH in another, and have 
them connect via Telnet if on the same laptop?

Before I start messing with the actual hardware (USB converter and TTY)?
thanks
Charles


-Original Message- 
From: J. David Bryan

Sent: Friday, September 13, 2019 6:23 PM
To: General Discussion: On-Topic and Off-Topic Posts
Cc: Charles
Subject: Re: Connecting SIMH to teletype via USB

On Friday, September 13, 2019 at 15:42, Charles via cctalk wrote:


I could use a hint... I have a USB to current-loop (Volpe) interface
board, and Windows 7 on my laptop does recognize it as COM4 at 110
baud. So far so good. No problem hooking it up to my ASR-33 Teletype.

Now I'd really like to figure out how to set SIMH to use the 33 as the
console, so the TTY will be attached to the virtual PDP-8.


Section 3.14, "Console Options" of the "SIMH Users' Guide V4.0" suggests
that:

 set console serial=com4;110-8n2

...should work (though you might need "7e2" or "7o2" instead, depending on
how your Teletype is set up).



Anything that starts with "set console..." gives a "no settable
parameters" error.


Does the above also give this error?

 -- Dave 



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Re: Connecting SIMH to teletype via USB

[Charles via cctalk]

Update: got my SIMH (set console telnet:23) talking to PuTTY in another 
window, via Telnet 127.0.0.1:23.

So it is possible ;)
Now it's time to hook up the actual TTY to the USB-current loop card and see 
what's what!



-Original Message- 
From: J. David Bryan

Sent: Friday, September 13, 2019 6:23 PM
To: General Discussion: On-Topic and Off-Topic Posts
Cc: Charles
Subject: Re: Connecting SIMH to teletype via USB

On Friday, September 13, 2019 at 15:42, Charles via cctalk wrote:


I could use a hint... I have a USB to current-loop (Volpe) interface
board, and Windows 7 on my laptop does recognize it as COM4 at 110
baud. So far so good. No problem hooking it up to my ASR-33 Teletype.

Now I'd really like to figure out how to set SIMH to use the 33 as the
console, so the TTY will be attached to the virtual PDP-8.


Section 3.14, "Console Options" of the "SIMH Users' Guide V4.0" suggests
that:

 set console serial=com4;110-8n2

...should work (though you might need "7e2" or "7o2" instead, depending on
how your Teletype is set up).



Anything that starts with "set console..." gives a "no settable
parameters" error.


Does the above also give this error?

 -- Dave 



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Re: Connecting SIMH to teletype via USB

[Charles via cctalk]

I got ahead of myself a little bit... forgot I still couldn't connect a 
serial port to SIMH.


Turns out my version of SIMH 3.08 was from 2008 or so... I just downloaded 
the latest version 4 from GitHub and sure enough it does accept SET CONSOLE 
SERIAL.

Now I just have to figure out the port name since it doesn't like COM4:
But I'm almost there :)


-Original Message- 
From: Charles

Sent: Friday, September 13, 2019 6:46 PM
To: J. David Bryan ; cctalk digest
Subject: Re: Connecting SIMH to teletype via USB

Update: got my SIMH (set console telnet:23) talking to PuTTY in another
window, via Telnet 127.0.0.1:23.
So it is possible ;)
Now it's time to hook up the actual TTY to the USB-current loop card and see
what's what!


-Original Message- 
From: J. David Bryan

Sent: Friday, September 13, 2019 6:23 PM
To: General Discussion: On-Topic and Off-Topic Posts
Cc: Charles
Subject: Re: Connecting SIMH to teletype via USB

On Friday, September 13, 2019 at 15:42, Charles via cctalk wrote:


I could use a hint... I have a USB to current-loop (Volpe) interface
board, and Windows 7 on my laptop does recognize it as COM4 at 110
baud. So far so good. No problem hooking it up to my ASR-33 Teletype.

Now I'd really like to figure out how to set SIMH to use the 33 as the
console, so the TTY will be attached to the virtual PDP-8.


Section 3.14, "Console Options" of the "SIMH Users' Guide V4.0" suggests
that:

 set console serial=com4;110-8n2

...should work (though you might need "7e2" or "7o2" instead, depending on
how your Teletype is set up).



Anything that starts with "set console..." gives a "no settable
parameters" error.


Does the above also give this error?

 -- Dave 



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Partial success (SIMH TSS/8), new problem has me stumped

[Charles via cctalk]

I finally managed to get TSS/8 running under SIMH V4... console on the 
laptop, a time-sharing line (TTIX port 23) on an ADM-3A (much quieter while 
debugging) :)
The interface is the Volpe current-loop to USB board, a small freeware 
program "COM By TCP" to allow a TCP port (USB is COM4, TCP is 127.0.0.1 port 
23).


So far so good. But I am having connection problems with the data coming 
from SIMH to the terminal.
At 110 baud I only get a few characters before the serial-TCP program hangs 
with this write-timeout message:


22:24:11:   Socket connected to 127.0.0.1:23
22:24:11:   SOCK: Unable to write on COM. The port is CLOSED.. <-- this is 
because I didn't "Get COM" first.

22:24:13:   COM4 correctly opened!
22:24:24:   System.TimeoutException: The write timed out.
  at System.IO.Ports.SerialStream.Write(Byte[] array, Int32 offset, Int32 
count, Int32 timeout)
  at System.IO.Ports.SerialPort.Write(Byte[] buffer, Int32 offset, Int32 
count)
  at COMbyTCP.Form.sockClient_dataRecived(Byte[] buffer, Int32 
bytesRecived)


I tried at 1200 baud and the same problem occurs, I can just get more 
characters before the terminal screen freezes.
Nothing's locked up except the downstream SIMH data (i.e. I can hit Return 
on the terminal and the TSS/8 dot prompt reappears).
It is repeatable regardless of what I am trying to do on the terminal. Only 
very small outputs come through in their entirety without this error 
message.
I don't think it's the current-loop board, which has an onboard micro fast 
enough to translate Baudot on the fly. And the receive light stops 
flickering at the same time the write timeout message pops up.


Does anyone know how I can extend the timeout parameter... is this a Windows 
networking problem, or something flaky in the freeware serial-TCP program?

thanks
Charles


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Looking for front panel switch

[Charles via cctalk]

This fall I decided to restore my first homebrewed computer that I made 
40(!) years ago and still have... a 2 MHz 8080A, 1K of static RAM, a 1702A 
(256 byte) EPROM, cobbled up an S-100 connector for a VB-1B video card, an 
8-bit I/O port that used an EBCDIC keyboard (ASCII translation table in the 
EPROM), and of course a hand-made front panel PC board with blinkenlights & 
switches. I had a good time learning assembly language (and 
hand-assembling)... I also toggled in WADUZITDO once or twice. That's a 
functional interpreted language in 256 bytes plus char in/out routine, for 
the youngsters ;)


I sold the VB-1B years ago, and can't find the keyboard which got lost in a 
move years ago. So if I want to play with small 8080 programs, I'll need to 
add a UART (and redo the primitive monitor program for serial I/O instead of 
memory-mapped display). Recently I bought one of Martin Eberhard's ME-1702A 
boards with pre-programmed PIC, acquired all the parts from junkbox and 
Mouser, and just got THAT working. Surprisingly enough, the monitor seems to 
still have all the right bits after 40 years.


Anyway. At some earlier time, I'd either lost (or cannibalized for a PDP-8) 
one of the switches. Subminiature SPDT toggle switches are readily available 
from C&K and Mountain, but I cannot find one with the four-pin mounting 
bracket and the "ears" to hold the paddle lever pivots. Attached is a 
picture showing part of the front panel.


https://imgur.com/bIrmZt7

Does anyone have a matching switch they're not using? I have a spare black 
lever, but it's supposed to be blue for that nibble which would be even 
better ;)

Thanks for any help.


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Re: Looking for front panel switch

[Charles via cctalk]

https://www.tedss.com/MT-SPDT-7101


Thanks :) It's only slightly different (the mounting pins look to be a bit 
closer together than my switches dated 1975, but I can drill a couple holes 
in the PC board, and swap my matching lever onto it.)
Certainly a lot closer than the totally non-matching chrome bat handle unit 
I stuck in there for now!

-Charles


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Cybernetics Data Products scrolling LED sign

[Charles via cctalk]

I'm trying to repair a partially functioning Cybernetics Data Products 
ADT-2002 scrolling LED sign from the early 80's. Previous owner said 
there was a power failure or lightning strike, don't remember which, and 
gave it to me. The brief version of the instructions are taped to the 
keyboard, and that is the only manual I can find.


Power supply is functional and delivering 5 volts where it should.

On boot it's supposed to say "UNIT OPERATIONAL" on the display before 
plugging in the keyboard ribbon cable. There is garbage displayed instead.


When the keyboard is plugged in, the display responds to start/stop 
scroll (green and red keys), and messages can be input. The memory 
(yellow key) and control (blue key) functions don't seem to work.


There actually is a microprocessor (8048 or 8051), but inside the 
keyboard only.


Another observation: The display only scrolls a couple of characters, 
jumps back to the beginning and repeats forever.


But the actual display board has a 24-pin Harris PROM (fuse link), seven 
2102's 1K memory for the 7 rows of LEDs and many 7400 TTL including  
4-bit counters, comparators and adders. No CPU at all, so it must be a 
state machine, and a fairly complex one at that unless some of the 
"smarts" are actually in the keyboard microprocessor. The cable from the 
keyboard connects directly to the PROM without any buffering.


I have found that only the lowest 4 bits of the memory address lines 
have activity on them, which explains why two characters scroll before 
it repeats (16 columns). I can't find anything strange looking (e.g. 
non-TTL levels) on the middle and upper nibbles except that they don't move.


There does not seem to be any information on this unit online. I'd like 
to find a repair manual (probably too long a long shot), but even a 
schematic would save a lot of hair pulling!


Thanks for any help.

Thinking of selling my PDP's

[Charles via cctalk]

I am getting closer to retirement (although not close enough) and I'm 
considering selling off my PDP stuff, especially if I downsize and move.


Everything's working, but I just no longer DO anything with either 
system... the adventure was acquiring all the pieces, fixing them and 
learning the software :)


Anyhow I have an 8/A with cloned Programmer's Panel (Vince Slyngstad and 
I made it around 2006) and limited function panel, 32K RAM board (also 
have core), Philipp Hachtmann's USB interface board, RX01 floppy, two 
RL02's, and a high-speed (optical) reel-to-reel paper tape reader. OS/8 
is up and running. Several spare RL02 packs. It's all in a tall DEC rack 
with an H-(something) power control box. The ASR-33 is not included, I'm 
keeping that.


Also an 11/23+ (11/03 chassis) in a corporate cabinet with two RL02's, a 
16-line serial interface, VT-220 terminal. Also an RQDX3 which is 
connected to a loose 3.5" TEAC floppy drive. Have RT-11XM, RT-11SJ and 
TSX-Plus 6.50 (all 16 timesharing ports are working too).


So, I am wondering if there's any market for them (preferably as 
complete systems). Shipping would be difficult due to the size/weight 
(I'm in rural south central Missouri). I'm not looking to give them 
away, or to part out, but would entertain reasonable package deals 
rather than deal with the "LQQK! RARE!!" bull on ebay.


I can send pics to interested parties. Let me know,

thanks!

Charles

The X-Cap-Files

[Charles via cctalk]

Today I was working on a new-to-me VT240 which hadn't been powered up in 
a long time (possibly 10 years). Hooked it up to an old 9" B&W CCTV 
monitor and everything was running fine for 20 minutes or so - when 
suddenly an astonishing amount of acrid whitish-gray smoke started 
pouring from the vents =8^ O


So I yanked the power cord out and took the case off. Sure enough, one 
if not both of the 0.1 uF X-caps on the line filter had cracked open and 
my nose confirmed that was the source of the stench.


Fortunately there is no damage to the PC board or surrounding components 
- even the caps don't look toasted, just split. Good thing I was sitting 
right there when they failed and could turn the power off immediately. 
I've read here and elsewhere about the spectacular failure modes of 
these caps, sometimes flames, but this is the first time I ever 
experienced it first hand. Maybe it's time for a look inside my VT220? ;)


-Charles

Malfunctioning VT240 - help please

[Charles via cctalk]

Until a few minutes ago, my VT240 was operating normally, but now it's 
unresponsive (fails during power-on self test).


Normal behavior was: display a checkerboard, then two different 
intensity all-white bands growing slowly up from the bottom of the 
screen, then a beep and the expected "VT240 Monitor Error 9" (because 
I'm using an old B&W composite monitor instead of the DEC VR201 with 
special cable). Thereafter, normal operation.


Now, it briefly displays the checkerboard (and all four keyboard lights 
turn on, then off); then the Lock and Wait lights come on and nothing 
else happens. Blank screen.


Power-OK light on the back is illuminated and 5.19 volts measured on the 
board. Haven't checked +12 (or the internally derived keyboard +5) yet.


Another possibly useful observation: I can press the Setup (or any 
other) key about four times and hear a keyclick sound each time. But 
then it stops playing the click sound if I keep pressing keys. This 
suggests that the interrupt on the CPU (a T11) is not being responded to.


The technical manual is very detailed but does not describe the 
specifics of the POST, which could be useful in locating the failed 
circuit (or firmware).


Can anyone with experience in debugging these terminals lend a hand? 
Should I even be looking at the main board, or the keyboard which also 
has an 8051 CPU??


thanks.

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

OK. the keyboard is working properly as far as I can tell, data is going 
in and out, and I even swapped it for the keyboard on my VT220 and the 
same symptoms persisted.


I just verified all four ROMs on the T11, and the ROM for the 8085, 
against the images I found on the MAME site. So far so good.


One interesting finding - two of the lines (DAL3 and DAL1) on the T11 do 
change states several times, but once the self-test has crashed, they 
stay high with almost one volt of "wiggle". All the other data/address 
lines are either high, low or switching between a good 1 and 0.


There are several places that the bus connects, including the ROMs, 
1-bit dynamic RAMs and various octal latches & bidirectional buffers. I 
connected a 10 ma VOM between each line and ground (to make sure a 
low-resistance path (such as in the 'LS245 at E55) wasn't forcing it 
high somehow.


All of the DAL15-0 lines requires more than 1.9 ma to bring it to ground 
(well, 50 mv burden at 250 mv full scale, anyway).


That leaves the unlikely possibility that one of the octal TTL devices, 
or ROMs. has developed a weird internal pathway that only interferes 
with DAL3 & 1 on some bit patterns, but not all the time. Seems like a 
zebra rather than a horse. The only part that drives multiple low-order 
DAL lines at once besides the E19-22 ROMs is the E55 LS245.


The T11 spec sheet says that a good logic 0 (<0.4 volt) should be 
possible with up to 3.2 ma sink... So I suspect the T11 has a couple of 
bad output pull-down transistors on those lines. Anyone got a spare T11 
chip I can buy or borrow? Or send you mine to plug into your board and 
see if it fails the same way? :)

thanks.

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

On 6/10/20 4:31 PM, Jon Elson wrote:

On 06/10/2020 12:48 PM, Charles via cctalk wrote:


That leaves the unlikely possibility that one of the octal TTL 
devices, or ROMs. has developed a weird internal pathway that only 
interferes with DAL3 & 1 on some bit patterns, but not all the time. 
Seems like a zebra rather than a horse. The only part that drives 
multiple low-order DAL lines at once besides the E19-22 ROMs is the 
E55 LS245.


Quite possible that this could happen when a specific device is 
driving the bus -- or that NOBODY is driving the bus in that state. 
When it is stuck at the ~1V level, try a resistor of about 1 K to 
ground on one of those lines.  If it moves several hundred mV lower, 
it is a TTL open circuit.  If it doesn't change at all, it is a bus 
contention (TWO drivers driving at once).


Jon


Yes, I've been experimenting with this. It's not 1 volt, it's 4 to 3 
volts and back again at the rate the lines should be switching :)


If it were contention caused by the LS245, the short circuit current 
would be far higher. I've also tried strapping the OE\ on the '245 high 
with no change. I removed all four ROMs and if there's bus contention it 
is not coming from them. Unfortunately the USART and UART are not in 
sockets, but no change when their chip selects are forced invalid.


Even more interestingly, I have discovered that when the T11 is crashed 
completely (e.g. after I slip with a scope probe on the DAL or other 
lines), if I connect DAL3 when at a steady high, through a 1K to ground, 
results in a 0-3 volt output switching at the instruction cycle rate 
with a slow risetime and a rapid fall! That is not possible if the bus 
were tristated or in contention...


There has to be something in the T11 internal drivers that is latching 
up somehow. It would really help to have another T11 aka 310 aka 
21-17311 ALSO aka KR1807VM1 (Russian clone) to try - but apparently the 
Atari enthusiasts have snapped them all up and I refuse to pay over $100 
for a tested working one on Ebay!

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

On 6/10/20 4:31 PM, Jon Elson wrote:

On 06/10/2020 12:48 PM, Charles via cctalk wrote:


That leaves the unlikely possibility that one of the octal TTL 
devices, or ROMs. has developed a weird internal pathway that only 
interferes with DAL3 & 1 on some bit patterns, but not all the time. 
Seems like a zebra rather than a horse. The only part that drives 
multiple low-order DAL lines at once besides the E19-22 ROMs is the 
E55 LS245.


Quite possible that this could happen when a specific device is 
driving the bus -- or that NOBODY is driving the bus in that state. 
When it is stuck at the ~1V level, try a resistor of about 1 K to 
ground on one of those lines.  If it moves several hundred mV lower, 
it is a TTL open circuit.  If it doesn't change at all, it is a bus 
contention (TWO drivers driving at once).


Jon


After much Googling, I discovered/remembered that the RQDX3 M7555 floppy 
controller card in my PDP-11/23+ system has a T11 CPU on board!


So I pulled the card and popped the T11 into the VT240. Guess what - the 
terminal still doesn't work!! Craptastic. At least it's not the most 
expensive and rarest part on the board... but now I'm really stumped. 
This isn't my first rodeo - in fact back in the 80's I used to design 
microprocessor systems for a living, and have continued to keep my hand 
in repairing my video arcade games and a PDP-8 system, among other 
projects.


Meanwhile... the T11 DAL lines are only connected to a few parts that 
can drive onto that local bus. Time to have a look at the glue logic for 
the DRAM selects. Although the ROM chip selects seem to work, maybe the 
DRAM or something else actually IS conflicting despite the mixed signals 
(pun intended) ;)


Time to break out the logic analyzer, and start burning pairs of 27256 
EPROMs with test programs. Maybe initially just fill them with NOP's 
(000240 octal) with a jump to zero at the end!

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

On 6/11/20 2:29 AM, Mattis Lind wrote:



torsdag 11 juni 2020 skrev Charles via cctalk <mailto:cctalk@classiccmp.org>>:



On 6/10/20 4:31 PM, Jon Elson wrote:

On 06/10/2020 12:48 PM, Charles via cctalk wrote:


That leaves the unlikely possibility that one of the octal
TTL devices, or ROMs. has developed a weird internal
pathway that only interferes with DAL3 & 1 on some bit
patterns, but not all the time. Seems like a zebra rather
than a horse. The only part that drives multiple low-order
DAL lines at once besides the E19-22 ROMs is the E55 LS245.

Quite possible that this could happen when a specific device
is driving the bus -- or that NOBODY is driving the bus in
that state. When it is stuck at the ~1V level, try a resistor
of about 1 K to ground on one of those lines.  If it moves
several hundred mV lower, it is a TTL open circuit.  If it
doesn't change at all, it is a bus contention (TWO drivers
driving at once).

Jon


After much Googling, I discovered/remembered that the RQDX3 M7555
floppy controller card in my PDP-11/23+ system has a T11 CPU on board!

So I pulled the card and popped the T11 into the VT240. Guess what
- the terminal still doesn't work!! Craptastic. At least it's not
the most expensive and rarest part on the board... but now I'm
really stumped. This isn't my first rodeo - in fact back in the
80's I used to design microprocessor systems for a living, and
have continued to keep my hand in repairing my video arcade games
and a PDP-8 system, among other projects.

Meanwhile... the T11 DAL lines are only connected to a few parts
that can drive onto that local bus. Time to have a look at the
glue logic for the DRAM selects. Although the ROM chip selects
seem to work, maybe the DRAM or something else actually IS
conflicting despite the mixed signals (pun intended) ;)

Time to break out the logic analyzer, and start burning pairs of
27256 EPROMs with test programs. Maybe initially just fill them
with NOP's (000240 octal) with a jump to zero at the end!



Now that you know the T11 is good I think it a good idea to attach a 
logic analyzer on the bus.


I would then disassemble the ROM code and match that with the logic 
analyzer execution trace. Then it should be possible to find out what 
is going on. If one can rely on the fault code on the keyboard it is 
able to pass tests 0 to 4 successfully. Of course I have no idea what 
these test really do but assuming they do some more than advanced 
things I doubt that they would work if there are severe bus contention.


If that would be the case I think the system would fail quite soon 
rather than on test 5. A guess is that this is a memory problem.


Good luck!

/Mattis


=

Thanks for the tip. I didn't see in the manuals that the keyboard light 
pattern was actually a binary code, but that makes sense! I would have 
expected an error message on the screen, but as I previously noted, the 
video system itself does not seem to be working properly.


Unfortunately my logic analyzer is an ancient Tek 7D01, the equivalent 
of stone tools rather than metal ;) It's not really suited for doing 
this kind of work, but it's what I have... I wonder if anyone has 
already disassembled the code?


The 4116's are soldered to the board, too. Since the memory map is shown 
in the tech manual I could write a simple memory test and burn an EPROM.


My fear is that one of the PALs has altered itself from tin-whisker 
migration (fuse regrowth) :(

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

On 6/11/20 10:31 AM, Mattis Lind wrote:





Now that you know the T11 is good I think it a good idea to
attach a logic analyzer on the bus.

I would then disassemble the ROM code and match that with the
logic analyzer execution trace. Then it should be possible to
find out what is going on. If one can rely on the fault code on
the keyboard it is able to pass tests 0 to 4 successfully. Of
course I have no idea what these test really do but assuming they
do some more than advanced things I doubt that they would work if
there are severe bus contention.

If that would be the case I think the system would fail quite
soon rather than on test 5. A guess is that this is a memory
problem.

Good luck!

/Mattis


=

Thanks for the tip. I didn't see in the manuals that the keyboard
light pattern was actually a binary code, but that makes sense! I
would have expected an error message on the screen, but as I
previously noted, the video system itself does not seem to be
working properly.

The VT100 also makes use of a binary code for the very early errors 
like ROM and RAM faults so assuming the same behaviour here is not 
that far fetched I think.


Unfortunately my logic analyzer is an ancient Tek 7D01, the
equivalent of stone tools rather than metal ;) It's not really
suited for doing this kind of work, but it's what I have... I
wonder if anyone has already disassembled the code?


Yes. The 7D01 was older than I expected. I thought maybe a HP1630 or 
possibly 1615 which is old...

I guess that the memory depth of the 7D01 is not that much.

Assuming that the CPU does a HALT when it stops it should stop 
reference memory so if you let your logic analyzer just store all 
addresses until it stops you might be able to find the last (whatever 
memory depth you have) instructions. Use the memory strobe to clock in 
the address into the logic analyzer. Then you can do hand disassembly 
of this part. Or load it into Ersatz-11 and SimH and do the disassembly.
But maybe it is a good idea to find a slightly more modern LA? Maybe a 
HP 166x (There is one 1661 on Ebay at $70) which is quite portable and 
easy to use. Or HP 167x which has much better memory depth.


The 4116's are soldered to the board, too. Since the memory map is
shown in the tech manual I could write a simple memory test and
burn an EPROM.

Yes. That could be an alternative. Maybe you can figure out how to 
communicate over the serial port. Perhaps you can write something 
simplistic that outputs something to the serial port?


My fear is that one of the PALs has altered itself from
tin-whisker migration (fuse regrowth) :(

That could probably happen. But I have seen more cases with failed 
memory chips than PALs that have self-altered.

/Mattis


===

The T11 is not halted - it's looping endlessly in the first ROM. There 
is a brief burst of DRAM select activity on the scope just before it 
hangs in the loop.


All the glue logic and memory map adders/multiplexers seem to be grossly 
working with outputs that change state. I was hoping to find a bad or 
immovable line on one of them... Now this makes me even more suspicious 
that there is a bad address (or block of addresses) in RAM and that's 
where the test is hanging.


My 7D01 (16 channels) is hopelessly outclassed here. I looked at that HP 
1661 but it does not appear to come with the probes, which are so often 
discarded by surplus or scrappers. (A similar aggravation with our 
classic computers, of course).


Unfortunately I only have one 27256 in the drawer, so have to order some 
more before making memory test PROMs...and I also have to figure out a 
simple way of outputting the RAM failure address!

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

On 6/11/20 3:15 PM, Mattis Lind wrote:


The T11 is not halted - it's looping endlessly in the first ROM. There 
is a brief burst of DRAM select activity on the scope just before it 
hangs in the loop.


 That burst of DRAM activity might indicate a DRAM problem. One thing 
I have tried in the past is to put a known good DRAM on top of one 
DRAM is the array. So to say in parallel. In the cases I have tried I 
managed to make systems pass the memory check. Then test each and 
every one in the DRAM array in the same way. Might be worth a try.




The 2681 https://www.nxp.com/docs/en/data-sheet/SCC2681.pdf shouldn't 
be to difficult to configure and is located on the same bus as the 
keyboard so you should be able to send something  on the UART to 
either the printer/aux or the host.




Thanks again. I have some 4116's on order too. I'll try the piggyback 
trick, and if it works, will desolder the offending RAM (and install a 
machined-pin socket!) I will probably never have to change it again - 
but the PC board wouldn't like another desolder operation...


If that doesn't work, then I'll start writing diagnostic software using 
the 2681. Of course then I have to debug the program before I can debug 
the terminal ;)

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

Make that "fuse-link PROMs". My mistake.

-Charles

On 6/15/20 10:41 AM, Tony Duell wrote:

My fear is that one of the PALs has altered itself from tin-whisker
migration (fuse regrowth) :(

I've finally looked at the printset for the VT240 and I must be
missing something

The only PALs I can find are the 'logic units' in the  video memory
updating circuitry. That circuitry is pretty much the same as  the
Rainbow colour graphics board and I suspect the PAL logic is much the
same too. I have the Rainbow's PAL equations if you need them but I
doubt that's the problem.

-tony

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

On 06/11/2020 02:29 AM, Mattis Lind via cctalk wrote:
>/If that would be the case I think the system would fail />/quite soon rather 
than on test 5. A guess is that this is />/a memory problem. /
That was a good guess, everyone ;) I got some new 4116's and piggybacked 
(dry, no solder) two of them atop my suspects at E3 & E4.


Didn't fix it. Of course :/

In the meantime I've acquired a nice HP 1630G logic analyzer complete 
with pods and cables. Setting it up was going to take quite a while 
since I'm not familiar with this model. So I decided to try a simple 
brute-force approach before the analyzer. I piggybacked another 4116 
onto each soldered-in 4116, one at a time. Actually easy to do since 
with the leads properly formed, I didn't even have to solder it in 
place, just turn off the power and move it to the next chip.


On the 16th, the last one of course, the terminal booted normally and 
works again. :)


I confirmed the bad one by removing the piggyback and the failure 
returned. Now I need to desolder the bad one without ruining the board. 
I may just cut the leads off close to the bad chip, and solder the 
replacement to the stumps. (Normally I remove the legs and install a 
machine-pin DIP socket). Or just solder the piggyback and leave it 
there... thoughts?

Re: Malfunctioning VT240 - help please

[Charles via cctalk]

On 6/21/20 10:41 AM, Jon Elson wrote:


On 06/20/2020 09:41 PM, Charles wrote:

On 6/20/20 8:31 PM, Jon Elson wrote:


I confirmed the bad one by removing the piggyback and the failure 
returned. Now I need to desolder the bad one without ruining the 
board. I may just cut the leads off close to the bad chip, and 
solder the replacement to the stumps. (Normally I remove the legs 
and install a machine-pin DIP socket). Or just solder the piggyback 
and leave it there... thoughts?


Cut the leads close to the body.  Apply a soldering iron to each 
lead, and pull the lead out with tweezers,
simultaneously heating and pulling.  This is very gentle to the 
board, just doing one at a time.  Then, you can vacuum out the holes 
and install a new chip or socket.


I've done this many times, and never wrecked a board.

Jon

That's how I do it... the vacuuming is the problem. Someday I need to 
get a good vacuum desoldering station. Right now I just have a 
spring-loaded solder sucker (which I can do a pretty decent job with 
on most boards). But this high-density layout (2 traces between DIP 
pads) I'm a bit wary of.


Just be gentle, and you should be able to do it.  Also, in some cases, 
you might heat from the opposite side from the solder sucker.  That 
way, you can keep the soldering iron on the pad until you have 
triggered the sucker.  But, yes, the hollow soldering iron with 
powered vacuum is amazing the first time you try it.  I got one at an 
auction years ago, it is much better than the regular iron and 
plunger-sucker.


Jon


The small company I first worked for had a Pace unit. I remember not 
being impressed with it - frequent clogs, pads lifting, and not getting 
all the solder out, no matter how we set things. Still beat solder-wick 
though!


I got it done, but pin 16 (which connects directly to the internal-layer 
ground plane) was a bear. From the feel of it and the heat required, the 
draftsman didn't bother to make pad reliefs. Anyway it's now socketed, 
so of course it will never fail again!


I also made a small jumper on a 15-pin D-sub to connect Monitor Present 
L to ground, so that annoying "Monitor Error 9" message stops ;) On to 
the next project!

[cctalk] Looking for TMS0106NC chip

[Charles via cctalk]

I hope a 1974 desk calculator (Radio Shack EC-2000, a re-badged TI-3500) 
is considered sufficiently both classic and computer for this list. :)


The one IC, a TI TMS0106NC, has failed and I'm searching everywhere for 
a replacement. There's an -0103 on ebay from the same family which would 
substitute, but it's only 8 digits and this is a 10 digit machine. Plus 
it's $31 with postage, more than the calculator itself is worth!


If anyone has one, or knows where I can get this IC, new or a pull, 
please let me know.


Thanks!

[cctalk] FS: PDP-11/23+ system

[Charles via cctalk]

Over the years, I have gradually built up a functional PDP-11/23+ 
system, which of course I now have no need for ;) So I'd be interested 
in selling it as I slowly downsize. You'd need to pick it up in south 
central Missouri as shipping would be impractical and expensive.


Specifics: 11/23+ with 4MB RAM, selectable boot ROMs, two RL02 drives, 
floppy interface (set to 3.5" TEAC drive), 16-line serial ports, 
corporate cabinet with DEC power controller. Software including RT-11SJ, 
XM, TSX-Plus. Also have a VT-220 for the console which I may sell 
separately or with the system.


Please email me *off-list* with offers, request for pics, etc.

thanks

Charles

[cctalk] Re: Random items on Pascal #3

[Charles via cctalk]

In the early '80's, I did some programming with Micro Concurrent Pascal, 
on embedded CDP1802 systems. It was really nice to be able to program in 
something other than assembly language (a cross-assembler that ran on a 
PDP-11 system).


Regarding protections, it didn't have many. I remember spending a day 
tracking down a fatal bug with a logic analyzer (emulators were still a 
dream in this small company)... another programmer had used an array 
subscript out of range and the compiler didn't catch it for some reason. 
So in this array defined [0..20], when the typo caused a write to 
FOO[60] instead of FOO[20], bad things happened.


Ah, the good old days ;)

-Charles

Re: IBM Rigid Cleaning Tool 2200574

[West, Charles via cctalk]

Chas and chon here at Daystar Television do you have or can you refer us  
finding