Re: VAXmate PSU

[Mattis Lind via cctalk]

Hello Rob,

söndag 29 mars 2020 skrev Rob Jarratt :

> Thanks Mattis. I do test it with a load, although to be honest I forgot to
> do this when I took the measurements yesterday. I use a modern-ish IDE disk
> and a load board from a MicroVAX 2000 as the dummy load. I don’t know if
> that is sufficient.
>
>
Do you know the nominal output rating for the supply?
It might be the case that even with load board the load is uneven. But it
sounds less likely.

>
>
> I don’t know enough about PSUs to make the secondary side drawing more
> logical unfortunately.
>
>
Can be hard. But a good idea is try to minimise the length of wires. Maybe
use designators for networks instead of wires to make the schematic more
readable. On the other hand I was reading the post on the iPad.

>
>
> I have a variac and a bench power supply, so I could do what you suggest.
>
> To stay safe you need a protection transformer as well. Otherwise the the
bench supply will end up at line potential. With the protection transformer
in place the circuit will be left floating in relation to earth. With a
variac you can then vary the input and keep it within safe limits. If you
don’t have a protection transformer and variac then another bench DC supply
that can give up to 100 V can be used instead.

>
> Could you be a bit more specific about where to apply what, so I don’t do
> it wrong or damage something? Would you put the bench PSU across the UC3842
> Vcc and Gnd pins? I am not sure what would happen if the normal supply to
> the UC3842 was still in place with the bench power supply also trying to
> supply power. Would it be wise to lift R32 so nothing conflicts with the
> bench power supply?
>
>
Absolutely right. I should have been more explicit about where to introduce
external supply. But as you say, lift R32 to isolate the switching
controller and feed in the bench supply current at VCC. Check the data
sheet for what is approriate voltage.

Good luck!

/Mattis

>
>
> Thanks
>
>
>
> Rob
>
>
>
> *From:* Mattis Lind 
> *Sent:* 29 March 2020 06:39
> *To:* r...@jarratt.me.uk; Rob Jarratt ;
> General Discussion: On-Topic and Off-Topic Posts 
> *Subject:* Re: VAXmate PSU
>
>
>
> Hello Rob,
>
> lördag 28 mars 2020 skrev Rob Jarratt via cctalk :
>
> I have posted here a couple of times because I have a failed VAXmate PSU. I
> have just posted a little bit more information here:
> https://robs-old-computers.com/2020/03/28/further-
> analysis-of-the-vaxmate-h7
> 270-psu-failure/ with some scope traces and a greatly improved schematic.
> Although the schematic is likely to have errors still. Unfortunately, a
> stray scope probe ground lead blew the fuse so now I have to wait for a new
> fuse to arrive before I can continue work.
>
>
>
> I would really like to know if all the spiking I am seeing is to be
> expected, and any suggestions why it appears to be detecting an
> overcurrent?
> There do not appear to be any shorts on the secondary side, but that could
> be wrong of course. I don't know if a genuine short anywhere would cause it
> to trip the SCR quite so quickly (within 20ms of the switching transistor
> starting to switch).
>
>
>
> This is fly back design and I would expect some spiking when the
> transistor shuts off.
>
>
>
> Then for over-current. It might be so that there are over-voltage
> protection on the outputs that kicks in. A crowbar that short circuits the
> output. It looks like there is such a circuit on 5 and 12 V. But to be
> honest the output circuit schematic is hard to read.
>
>
>
> If you have no load or little load or un-even load the PSU might hae
> problems to regulate. I know for fact that the PSU in the MicroVAX 2000
> need to have a dummy load when no hard drive is installed otherwise there
> will be uneven load which it has hard time to handle sonce the output
> regulation is based on the sum of the outputs somehow. It will trip the
> crowbar on over voltage on one of the outputs otherwise.
>
>
>
> What if you supply the control circuitry on the primary side using a bench
> lab supply and then connect a protection transformer and a variac in series
> to the normal AC inlet.
>
>
>
> Slowly increase input AC voltage while monitoring source voltage and
> output voltages.  At what AC input voltages does it trip? What is the
> output voltages at this point?
>
>
>
> If both voltages exceed normal and the crowbar trips I would think that
> the feedback network somehow reports to low output voltage to the control
> circuitry. Maybe the opto coupler is bad?
>
>
>
> Sorry. A lot of guessing here. But it is hard to tell withour more
> measurements.
>
>
>
> /Mattis
>
>
>
>
>
> Any thoughts gratefully received.
>
>
>
> Thanks
>
>
>
> Rob
>
>

Re: VAXmate PSU

[Matt Burke via cctalk]

On 29/03/2020 08:50, Mattis Lind via cctalk wrote:
> Hello Rob,
>
> söndag 29 mars 2020 skrev Rob Jarratt :
>
>> Thanks Mattis. I do test it with a load, although to be honest I forgot to
>> do this when I took the measurements yesterday. I use a modern-ish IDE disk
>> and a load board from a MicroVAX 2000 as the dummy load. I don’t know if
>> that is sufficient.
>>
>>
> Do you know the nominal output rating for the supply?
> It might be the case that even with load board the load is uneven. But it
> sounds less likely.

The output specifications for the H7270 power supply are on page 9-13 of
the VAXmate Technical Description (EK-PC500-TD-001).

+5.1V - Min 6.40A, Max 10.24A
+12.1 - Min 0.17A, Max 1.37A
-12.0 - Min 0.12A, Max 0.33A
+28.0 - Min 0.45A, Max 0.55A
-9.0 - Min 0.18A, Max 0.20A
300 - Min 0.00A, Max 0.46A (for the expansion box)

I have one of those load boards from a MicroVAX 2000 but the 5V load was
not connected by default. I had to install some zero ohm resistors. The
board I have draws 1A at 12V and 3A at 5V so you will need more load on
the 5V rail at least.

As Mattis has mentioned there looks to be a crowbar circuit on the
secondary side (Q2) to provide overvoltage protection. The 5V and 12V
output are shorted by Q2, which causes the primary side to sense an
overcurrent condition and shut the supply down.

Matt

RE: VAXmate PSU

[Rob Jarratt via cctalk]

Thanks, I do have an isolating transformer as well, so I will use that. I have 
done previous tests with a bench PSU on the UC3842 and found it needs 16V to 
get going. I just checked the Technical Description and it says the minimum 
current on the 5V output is 6.4A and on 12V it is 0.17A. I checked my load 
board and it is only going to sink 3A, so I need more load as I think the IDE 
disk is not going to be much. Would insufficient load really cause it to 
shutdown so quickly though?

 

Not sure I understand your comment about “designators for networks”, is there 
an example you can point me at? One of the things I have tried to do, but 
clearly not very successfully, is to minimise the lengths of the wires.

 

Regards

 

Rob

 

From: Mattis Lind  
Sent: 29 March 2020 08:51
To: r...@jarratt.me.uk
Cc: General Discussion: On-Topic and Off-Topic Posts 
Subject: Re: VAXmate PSU

 

Hello Rob,

söndag 29 mars 2020 skrev Rob Jarratt mailto:robert.jarr...@ntlworld.com> >:

Thanks Mattis. I do test it with a load, although to be honest I forgot to do 
this when I took the measurements yesterday. I use a modern-ish IDE disk and a 
load board from a MicroVAX 2000 as the dummy load. I don’t know if that is 
sufficient.

 

Do you know the nominal output rating for the supply?

It might be the case that even with load board the load is uneven. But it 
sounds less likely.  

 

I don’t know enough about PSUs to make the secondary side drawing more logical 
unfortunately.

 

Can be hard. But a good idea is try to minimise the length of wires. Maybe use 
designators for networks instead of wires to make the schematic more readable. 
On the other hand I was reading the post on the iPad. 

 

I have a variac and a bench power supply, so I could do what you suggest. 

To stay safe you need a protection transformer as well. Otherwise the the bench 
supply will end up at line potential. With the protection transformer in place 
the circuit will be left floating in relation to earth. With a variac you can 
then vary the input and keep it within safe limits. If you don’t have a 
protection transformer and variac then another bench DC supply that can give up 
to 100 V can be used instead. 

 

Could you be a bit more specific about where to apply what, so I don’t do it 
wrong or damage something? Would you put the bench PSU across the UC3842 Vcc 
and Gnd pins? I am not sure what would happen if the normal supply to the 
UC3842 was still in place with the bench power supply also trying to supply 
power. Would it be wise to lift R32 so nothing conflicts with the bench power 
supply? 

 

Absolutely right. I should have been more explicit about where to introduce 
external supply. But as you say, lift R32 to isolate the switching controller 
and feed in the bench supply current at VCC. Check the data sheet for what is 
approriate voltage. 

 

Good luck!

 

/Mattis

 

Thanks

 

Rob

 

From: Mattis Lind <  mattisl...@gmail.com> 
Sent: 29 March 2020 06:39
To:   r...@jarratt.me.uk; Rob Jarratt < 
 robert.jarr...@ntlworld.com>; General 
Discussion: On-Topic and Off-Topic Posts <  
cctalk@classiccmp.org>
Subject: Re: VAXmate PSU

 

Hello Rob,

lördag 28 mars 2020 skrev Rob Jarratt via cctalk mailto:cctalk@classiccmp.org> >:

I have posted here a couple of times because I have a failed VAXmate PSU. I
have just posted a little bit more information here:
https://robs-old-computers.com/2020/03/28/further-analysis-of-the-vaxmate-h7 

 
270-psu-failure/ with some scope traces and a greatly improved schematic.
Although the schematic is likely to have errors still. Unfortunately, a
stray scope probe ground lead blew the fuse so now I have to wait for a new
fuse to arrive before I can continue work.



I would really like to know if all the spiking I am seeing is to be
expected, and any suggestions why it appears to be detecting an overcurrent?
There do not appear to be any shorts on the secondary side, but that could
be wrong of course. I don't know if a genuine short anywhere would cause it
to trip the SCR quite so quickly (within 20ms of the switching transistor
starting to switch).

 

This is fly back design and I would expect some spiking when the transistor 
shuts off.  

 

Then for over-current. It might be so that there are over-voltage protection on 
the outputs that kicks in. A crowbar that short circuits the output. It looks 
like there is such a circuit on 5 and 12 V. But to be honest the output circuit 
schematic is hard to read. 

 

If you have no load or little load or un-even load the PSU might hae problems 
to regulate. I know for fact that the PSU in the MicroVAX 2000 need to have a 
dummy load when no hard drive is installed otherwise there will be uneven load 
which it has hard time to handle sonce

RE: VAXmate PSU

[Rob Jarratt via cctalk]

> -Original Message-
> From: cctalk  On Behalf Of Matt Burke via
> cctalk
> Sent: 29 March 2020 10:41
> To: cctalk@classiccmp.org
> Subject: Re: VAXmate PSU
> 
> On 29/03/2020 08:50, Mattis Lind via cctalk wrote:
> > Hello Rob,
> >
> > söndag 29 mars 2020 skrev Rob Jarratt :
> >
> >> Thanks Mattis. I do test it with a load, although to be honest I
> >> forgot to do this when I took the measurements yesterday. I use a
> >> modern-ish IDE disk and a load board from a MicroVAX 2000 as the
> >> dummy load. I don’t know if that is sufficient.
> >>
> >>
> > Do you know the nominal output rating for the supply?
> > It might be the case that even with load board the load is uneven. But
> > it sounds less likely.
> 
> The output specifications for the H7270 power supply are on page 9-13 of the
> VAXmate Technical Description (EK-PC500-TD-001).
> 
> +5.1V - Min 6.40A, Max 10.24A
> +12.1 - Min 0.17A, Max 1.37A
> -12.0 - Min 0.12A, Max 0.33A
> +28.0 - Min 0.45A, Max 0.55A
> -9.0 - Min 0.18A, Max 0.20A
> 300 - Min 0.00A, Max 0.46A (for the expansion box)
> 
> I have one of those load boards from a MicroVAX 2000 but the 5V load was not
> connected by default. I had to install some zero ohm resistors. The board I 
> have
> draws 1A at 12V and 3A at 5V so you will need more load on the 5V rail at
> least.


Thanks Matt, I just found that bit in the documentation and realised I am not 
generating enough load. I will have to add more. I did connect the 5V load 
because as you say it wasn't connected.


> 
> As Mattis has mentioned there looks to be a crowbar circuit on the secondary
> side (Q2) to provide overvoltage protection. The 5V and 12V output are shorted
> by Q2, which causes the primary side to sense an overcurrent condition and
> shut the supply down.


I can't test it now until I get another fuse, but I am sure I didn't see this 
happen, although it seems to be quite hard to tell.


> 
> Matt

H7874 power supply

[Robert Armstrong via cctalk]

  Does anybody have a maintenance print or service manual for the DEC H7874?
This is the power supply used in the BA4xx and R400x cabinets.  As you might
guess, I have one that tries to power up but shuts down after a second.
Probably a bad capacitor (or several), but this thing is ridiculously
complicated and not all that easy to disassemble, either.  I'd like to be
able to trouble shoot it rather than just firing the proverbial parts cannon
at it.  FWIW, none of the electrolytic (of which there are many) have
obviously failed - no leaking, no bulges, etc.  Of course, that proves
fairly little.

 

Thanks,

Bob Armstrong

 

RE: H7874 power supply

[Rob Jarratt via cctalk]

> -Original Message-
> From: cctech  On Behalf Of Robert
> Armstrong via cctech
> Sent: 29 March 2020 02:29
> To: cct...@classiccmp.org
> Subject: H7874 power supply
> 
>   Does anybody have a maintenance print or service manual for the DEC
> H7874?
> This is the power supply used in the BA4xx and R400x cabinets.  As you
might
> guess, I have one that tries to power up but shuts down after a second.
> Probably a bad capacitor (or several), but this thing is ridiculously
complicated
> and not all that easy to disassemble, either.  I'd like to be able to
trouble shoot
> it rather than just firing the proverbial parts cannon at it.  FWIW, none
of the
> electrolytic (of which there are many) have obviously failed - no leaking,
no
> bulges, etc.  Of course, that proves fairly little.
> 

This PSU is a real problem, as you say, complicated and hard to disassemble.
I had one that didn't work, if I remember correctly in the end I had to get
another one. I have a second machine with this PSU which has an intermittent
problem and shuts itself down after a few minutes if it hasn't been used for
a while, but a subsequent power up sees it work for as long as I need it.

It looks like I reverse engineered the schematic of the 12V output board. I
don't know if that would be of any use? How correct it is I don't know.

Regards

Rob


> 
> 
> Thanks,
> 
> Bob Armstrong
> 
> 

Re: H7874 power supply

[Holm Tiffe via cctalk]

Rob Jarratt via cctech wrote:

> 
> 
> > -Original Message-
> > From: cctech  On Behalf Of Robert
> > Armstrong via cctech
> > Sent: 29 March 2020 02:29
> > To: cct...@classiccmp.org
> > Subject: H7874 power supply
> > 
> >   Does anybody have a maintenance print or service manual for the DEC
> > H7874?
> > This is the power supply used in the BA4xx and R400x cabinets.  As you
> might
> > guess, I have one that tries to power up but shuts down after a second.
> > Probably a bad capacitor (or several), but this thing is ridiculously
> complicated
> > and not all that easy to disassemble, either.  I'd like to be able to
> trouble shoot
> > it rather than just firing the proverbial parts cannon at it.  FWIW, none
> of the
> > electrolytic (of which there are many) have obviously failed - no leaking,
> no
> > bulges, etc.  Of course, that proves fairly little.
> > 
> 
> This PSU is a real problem, as you say, complicated and hard to disassemble.
> I had one that didn't work, if I remember correctly in the end I had to get
> another one. I have a second machine with this PSU which has an intermittent
> problem and shuts itself down after a few minutes if it hasn't been used for
> a while, but a subsequent power up sees it work for as long as I need it.
> 
> It looks like I reverse engineered the schematic of the 12V output board. I
> don't know if that would be of any use? How correct it is I don't know.
> 
> Regards
> 
> Rob
> 
> 
I would be interested. I have an VAX400/300 with such an working again
PSU, Changed Capacitors two years before..now it works. A friend gave me
another PSU with a similar fault, changed capacitors as before on the
other one..but no luck at all. It still powers down shortly after
switching on. Yes..thats the most ugly PSU Design I ever saw..and I'm
interested in schematics or parts of them..

Regards,

Holm
-- 
  Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, 
 Freiberger Straße 42, 09600 Oberschöna, USt-Id: DE253710583
i...@tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741

Monitors FTGH

[Antonio Carlini via cctalk]

The following four monitors are available free for pickup in the UK 
(OX17 postcode).



All appear clean but are untested. All are believed to have been 
functional when stored but that was ~2002/2003-ish.



Microvitec Cub. Seems to be in its original box.

DEC VRT19-D3.

Vision Master Pro 17.

DEC VRC21-W3.


Obviously with the current restrictions on movement these cannot be 
picked up, but they need to be gone soon after the restrictions are over.



Expressions of interest offlist please.


Antonio


--
Antonio Carlini
anto...@acarlini.com

Re: DIBOL and RPG for RSTS

[Paul Koning via cctalk]

> On Mar 28, 2020, at 2:55 PM, dwight via cctalk  wrote:
> 
> There are a few reasons most don't like Forth:
> 
>  1.   no type checking ( suppose to save dumb programmers )
>  2.   Often, no floating point. ( Math has to be well thought out but when 
> done right in integer math it has few bugs ).
>  3.  Few libraries ( One can often make code to attach to things like C 
> libraries but it is a pain in the A. Often if you know what needs to be done 
> it is easier and better to write your own low level code. Things like USB are 
> tough to get at the low level stuff, though )
>  4.  To many cryptic symbols ( : , . ! @ ; )
>  5.  To much stack noise ( dup swap rot over )
> 
> I still use Forth for all my hobby work. It is the easiest language to get 
> something working of any of the languages I've worked with.
> ...
> Learning to be effective with Forth has a relatively steep learning curve. 
> You have to understand the compiler and how it deals with your source code. 
> You need to get used to proper comments to handle stack usage. You need to 
> learn how to write short easily test words ( routines ). It is clearly not 
> just a backwards LISP. It is not Python either.
> Dwight

No, it certainly isn't Python, which is my other major fast-coding language.

FORTH started as a small fast real-time control language; its inventor worked 
in an observatory and needed a way to control telescopes.  It's still used for 
that today.  I recently went looking for FORTH processors in FPGA, there are 
several.  One that looked very good was designed for robotics and machine 
vision work.  The designer posted both the FPGA design and the software, which 
includes a TCP/IP (or UDP/IP ?) stack.  He reports that the code is both much 
smaller and faster than compiled C code running on conventional FPGA embedded 
processors.

paul

Re: DIBOL and RPG for RSTS

[Kevin Monceaux via cctalk]

On Sat, Mar 28, 2020 at 06:55:34PM +, dwight via cctalk wrote:

> It is clearly not just a backwards LISP.

LISP is another language that I shied away from in the past, but finally
started exploring a while back.

> It is not Python either.

There's another point in its favor.  I've tried to develop a fondness for
Python over the years.  It hasn't happened yet.

The languages I've used most are probably Perl and Clipper.  At work before
we retired our mainframe I did a little COBOL, EasyTrieve, and Gener/OL
programming.  Now that we've migrated to an IBM i platform, I've done some
CL and RPG programming.





-- 

Kevin
http://www.RawFedDogs.net
http://www.Lassie.xyz
http://www.WacoAgilityGroup.org
Bruceville, TX

What's the definition of a legacy system? One that works!
Errare humanum est, ignoscere caninum.

Re: DIBOL and RPG for RSTS

[Guy Sotomayor via cctalk]

On Sun, 2020-03-29 at 10:21 -0400, Paul Koning via cctalk wrote:
> > On Mar 28, 2020, at 2:55 PM, dwight via cctalk <
> > cctalk@classiccmp.org> wrote:
> > 
> > There are a few reasons most don't like Forth:
> > 
> >  1.   no type checking ( suppose to save dumb programmers )
> >  2.   Often, no floating point. ( Math has to be well thought out
> > but when done right in integer math it has few bugs ).
> >  3.  Few libraries ( One can often make code to attach to things
> > like C libraries but it is a pain in the A. Often if you know what
> > needs to be done it is easier and better to write your own low
> > level code. Things like USB are tough to get at the low level
> > stuff, though )
> >  4.  To many cryptic symbols ( : , . ! @ ; )
> >  5.  To much stack noise ( dup swap rot over )
> > 
> > I still use Forth for all my hobby work. It is the easiest language
> > to get something working of any of the languages I've worked with.
> > ...
> > Learning to be effective with Forth has a relatively steep learning
> > curve. You have to understand the compiler and how it deals with
> > your source code. You need to get used to proper comments to handle
> > stack usage. You need to learn how to write short easily test words
> > ( routines ). It is clearly not just a backwards LISP. It is not
> > Python either.
> > Dwight
> 
> No, it certainly isn't Python, which is my other major fast-coding
> language.
> 
> FORTH started as a small fast real-time control language; its
> inventor worked in an observatory and needed a way to control
> telescopes.  It's still used for that today.  I recently went looking
> for FORTH processors in FPGA, there are several.  One that looked
> very good was designed for robotics and machine vision work.  The
> designer posted both the FPGA design and the software, which includes
> a TCP/IP (or UDP/IP ?) stack.  He reports that the code is both much
> smaller and faster than compiled C code running on conventional FPGA
> embedded processors.
> 
Yes, that would be J1.  I've used it and even wrote a simulator for it
(in FORTH 'natch) so that I could debug my code.  It's a useful FPGA
implementation.

TTFN - Guy

Re: Monitors FTGH

[Adrian Graham via cctalk]

> On 29 Mar 2020, at 11:27, Antonio Carlini via cctalk  
> wrote:
> 
> The following four monitors are available free for pickup in the UK (OX17 
> postcode).
> 
> 
> All appear clean but are untested. All are believed to have been functional 
> when stored but that was ~2002/2003-ish.
> 
> 
> Microvitec Cub. Seems to be in its original box.

Ah dammit, I wish I’d known you had that when you came up to relieve me of some 
tape stuff I’d rescued from work

I too have some honking great monitors to give away, including my main VRT19 
that was my DECstation then Alpha 3000 monitor at work back in the 90s. I’m 
surprised at how brown it’s gone.

-- 
Adrian Graham
Owner of Binary Dinosaurs, the UK's biggest private home computer collection?
t: @binarydinosaursf: facebook.com/binarydinosaurs
w: www.binarydinosaurs.co.uk

RE: VAXmate PSU

[Fred Cisin via cctalk]

On Sun, 29 Mar 2020, Rob Jarratt via cctalk wrote:
Thanks Mattis. I do test it with a load, although to be honest I forgot 
to do this when I took the measurements yesterday. I use a modern-ish 
IDE disk and a load board from a MicroVAX 2000 as the dummy load. I 
don’t know if that is sufficient.


I have NO specific knowledge of that PSU.

However, it seems likely that a "modern-sh IDE disk" in unlikely to be 
enough load.



OB_useless_nostalgia:
In the old days, we used an automotive headlight bulb.  That also provided 
a lot, even excess, light on the workbench.  Since my microcomputer days 
overlapped the period that I ran a Honda car repair shop (until 1980), I 
used to save any dual filament (High/low) bulbs that we replaced due to 
ONE of the filaments burning out.  I made an aimable mount for my 
workbench load out of an early VW headlight mount.

RE: H7874 power supply

[Robert Armstrong via cctalk]

> Rob Jarratt >robert.jarr...@ntlworld.com> wrote:
> I reverse engineered the schematic of the 12V output board. I
>don't know if that would be of any use? How correct it is I don't know.

  Sure, if you don't mind sharing.  Everything helps.

  Looks like there are five separate PCBs in there.  There's one long,
skinny one that's obviously the AC input and rectifier board, which probably
produces something like 300VDC for the regulator boards.  There are two
similar but not identical boards with huge heat sinks that are obviously the
output regulators.  I think this PS has +5, +3.3, +12 and -12 volt outputs,
but I've no idea which board does which.  

  And then there's a giant PCB, almost 11" square, covered with opamps, 74LS
logic and discrete parts.  There are filter caps, a transformer, and
switching transistors on this board too so it obviously produces yet another
power output for something.  Oh, and I think this cabinet has variable speed
fans, right?  SO there's probably a fan speed controller on here as well.

  You'd think that will all this logic it could at least have some LEDs or
something to tell me which output has failed, but it doesn't seem like it.  

Thanks
Bob

RE: H7874 power supply

[Rob Jarratt via cctalk]

OK, I posted it here:
https://robs-old-computers.com/2020/03/29/h7874-power-supply/


> -Original Message-
> From: Robert Armstrong 
> Sent: 29 March 2020 15:44
> To: r...@jarratt.me.uk; 'General Discussion: On-Topic Posts'
> 
> Subject: RE: H7874 power supply
> 
> > Rob Jarratt >robert.jarr...@ntlworld.com> wrote:
> > I reverse engineered the schematic of the 12V output board. I don't
> >know if that would be of any use? How correct it is I don't know.
> 
>   Sure, if you don't mind sharing.  Everything helps.
> 
>   Looks like there are five separate PCBs in there.  There's one long,
skinny one
> that's obviously the AC input and rectifier board, which probably produces
> something like 300VDC for the regulator boards.  There are two similar but
not
> identical boards with huge heat sinks that are obviously the output
regulators.  I
> think this PS has +5, +3.3, +12 and -12 volt outputs, but I've no idea
which board
> does which.
> 
>   And then there's a giant PCB, almost 11" square, covered with opamps,
74LS
> logic and discrete parts.  There are filter caps, a transformer, and
switching
> transistors on this board too so it obviously produces yet another power
output
> for something.  Oh, and I think this cabinet has variable speed fans,
right?  SO
> there's probably a fan speed controller on here as well.
> 
>   You'd think that will all this logic it could at least have some LEDs or
> something to tell me which output has failed, but it doesn't seem like it.
> 
> Thanks
> Bob

RE: H7874 power supply

[Maciej W. Rozycki via cctalk]

On Sun, 29 Mar 2020, Robert Armstrong via cctech wrote:

>   And then there's a giant PCB, almost 11" square, covered with opamps, 74LS
> logic and discrete parts.  There are filter caps, a transformer, and
> switching transistors on this board too so it obviously produces yet another
> power output for something.  Oh, and I think this cabinet has variable speed
> fans, right?  SO there's probably a fan speed controller on here as well.

 There's logic included there for synchronised control of multiple H7874 
PSUs at once in a master-slave configuration via a set of auxiliary 
connectors so as to power up or down all pieces simultaneously in a 
complex machine setup with storage and/or Q-bus expansion boxes.  No 
documentation for the PSU has been chased so far as far as I know.

 Note that also with this PSU there were capacitors used that suffered 
from the issue with the quaternary ammonium salt system used in the 
electrolyte.  All mine had numerous Chemi-Con SXF parts scattered across 
all boards, some leaking.  They are prone to leaks even if unused and have 
to be replaced.  Especially those next to the 5V circuit are hard to get 
to to desolder and replace.  Also Chemi-Con SXE parts present in this PSU 
are reportedly affected although I haven't seen them leak myself.

 This PSU has been my worst nightmare as far as keeping old equipment 
alive has been concerned.  I was able to make just one working PSU out of 
three broken ones by mixing and matching individual pieces with caps 
replaced until I found one set that worked.  I consider replacing the 
large cuboid 6800µF Sprague part as well as I have seen its capacitance 
drop down to like half of its nominal.

  Maciej

Re: H7874 power supply

[Paul Koning via cctalk]

> On Mar 29, 2020, at 2:14 PM, Robert Armstrong via cctech 
>  wrote:
> 
>> Maciej W. Rozycki  wrote:
>> numerous Chemi-Con SXF parts scattered across 
>> all boards, some leaking
> 
>  Yeah, mine is full of "Nippon Chemi-Con" electrolytic too.  
> 
>  What about just gutting the PS chassis and sticking in an ATX power supply?  
> I don't know how the maximum current per output breaks down, but as I 
> understand it the H7874 is only a 600W supply.  That's not a problem for an 
> ATX supply, and it would have all the required output voltages.  You'd have 
> to run the cabinet fans at a fixed speed and you'd lose the power control bus 
> feature, but that's not a show stopper.
> 
>  Actually my unit is in an R400x chassis full of RF drives, so I believe I 
> only need +12 and +5.  I don't think the 3.3v and -12 are used in that case.  
> I wonder how much current I really need for the drives?  I should look that 
> up and I might be able to find a surplus dual output supply that would do the 
> job.

I had a similar thought for a PRO supply that blew its input filter (of all 
things).  It does +5, +12, and -12.  The -12 is needed at least for RS232.

paul

Re: PDP-8 Straight 8 restoration

[Diane Bruce via cctalk]

On Mon, Mar 30, 2020 at 09:47:51AM +1300, Brendan McNeill via cctech wrote:
> Here in NZ and around the world many of us are in lockdown and spending more 
> time on our computers, if that were possible.  I have just completed the 
> restoration of a PDP-8 Straight 8 which I believe is the only one in New 
> Zealand.  You can view the restoration story and find appropriate resources 
> here:  https://pdp-8.nz    
> 
> While it plays Chess, it would be great if someone wanted to write (say) a 
> Prime Number Generator, or some other application and email it to me off 
> list.  I have Focal-69 and can probably source other languages for this 
> wonderful old machine with 4K of memory.

I have memories of keying in RIM and BIN. Long long time ago. I also learned
how to talk to the OS/8 file system so we could play morse code from a file
instead of a paper tape for our University club station. ;)

> --//
> bren...@mcneill.co.nz
> +64 21 881 883
> 
> 
> 
> 

73 de VA3DB for those that care ;)
-- 
- d...@freebsd.org d...@db.net http://www.db.net/~db

RE: H7874 power supply

[Robert Armstrong via cctalk]

>Maciej W. Rozycki  wrote:
>numerous Chemi-Con SXF parts scattered across 
>all boards, some leaking

  Yeah, mine is full of "Nippon Chemi-Con" electrolytic too.  

  What about just gutting the PS chassis and sticking in an ATX power supply?  
I don't know how the maximum current per output breaks down, but as I 
understand it the H7874 is only a 600W supply.  That's not a problem for an ATX 
supply, and it would have all the required output voltages.  You'd have to run 
the cabinet fans at a fixed speed and you'd lose the power control bus feature, 
but that's not a show stopper.

  Actually my unit is in an R400x chassis full of RF drives, so I believe I 
only need +12 and +5.  I don't think the 3.3v and -12 are used in that case.  I 
wonder how much current I really need for the drives?  I should look that up 
and I might be able to find a surplus dual output supply that would do the job.

Thanks again,
Bob

RE: H7874 power supply

[Rob Jarratt via cctalk]

I have some notes I made about trying a PC PSU, I don't think it really worked, 
there are signals to indicate power OK and perhaps others. But perhaps a more 
concerted effort might yield something that could work.

Regards

Rob

> -Original Message-
> From: cctech  On Behalf Of Robert
> Armstrong via cctech
> Sent: 29 March 2020 19:15
> To: 'Maciej W. Rozycki' ; 'General Discussion: On-
> Topic Posts' 
> Cc: r...@jarratt.me.uk
> Subject: RE: H7874 power supply
> 
> >Maciej W. Rozycki  wrote:
> >numerous Chemi-Con SXF parts scattered across all boards, some leaking
> 
>   Yeah, mine is full of "Nippon Chemi-Con" electrolytic too.
> 
>   What about just gutting the PS chassis and sticking in an ATX power supply? 
>  I
> don't know how the maximum current per output breaks down, but as I
> understand it the H7874 is only a 600W supply.  That's not a problem for an
> ATX supply, and it would have all the required output voltages.  You'd have to
> run the cabinet fans at a fixed speed and you'd lose the power control bus
> feature, but that's not a show stopper.
> 
>   Actually my unit is in an R400x chassis full of RF drives, so I believe I 
> only need
> +12 and +5.  I don't think the 3.3v and -12 are used in that case.  I wonder 
> how
> much current I really need for the drives?  I should look that up and I might 
> be
> able to find a surplus dual output supply that would do the job.
> 
> Thanks again,
> Bob

RE: H7874 power supply

[Rob Jarratt via cctalk]

I forgot to mention that I replaced a fair number of capacitors, even ones that 
had not leaked, because their ESR was a bit suspect. I have some notes, but it 
is hard to reconstruct exactly what I did.

Regards

Rob

> -Original Message-
> From: cctech  On Behalf Of Maciej W.
> Rozycki via cctech
> Sent: 29 March 2020 17:18
> To: b...@jfcl.com; General Discussion: On-Topic Posts
> 
> Cc: r...@jarratt.me.uk
> Subject: RE: H7874 power supply
> 
> On Sun, 29 Mar 2020, Robert Armstrong via cctech wrote:
> 
> >   And then there's a giant PCB, almost 11" square, covered with
> > opamps, 74LS logic and discrete parts.  There are filter caps, a
> > transformer, and switching transistors on this board too so it
> > obviously produces yet another power output for something.  Oh, and I
> > think this cabinet has variable speed fans, right?  SO there's probably a 
> > fan
> speed controller on here as well.
> 
>  There's logic included there for synchronised control of multiple H7874 PSUs 
> at
> once in a master-slave configuration via a set of auxiliary connectors so as 
> to
> power up or down all pieces simultaneously in a complex machine setup with
> storage and/or Q-bus expansion boxes.  No documentation for the PSU has
> been chased so far as far as I know.
> 
>  Note that also with this PSU there were capacitors used that suffered from 
> the
> issue with the quaternary ammonium salt system used in the electrolyte.  All
> mine had numerous Chemi-Con SXF parts scattered across all boards, some
> leaking.  They are prone to leaks even if unused and have to be replaced.
> Especially those next to the 5V circuit are hard to get to to desolder and
> replace.  Also Chemi-Con SXE parts present in this PSU are reportedly affected
> although I haven't seen them leak myself.
> 
>  This PSU has been my worst nightmare as far as keeping old equipment alive
> has been concerned.  I was able to make just one working PSU out of three
> broken ones by mixing and matching individual pieces with caps replaced until 
> I
> found one set that worked.  I consider replacing the large cuboid 6800µF
> Sprague part as well as I have seen its capacitance drop down to like half of 
> its
> nominal.
> 
>   Maciej

PDP-8 Straight 8 restoration

[Brendan McNeill via cctalk]

Here in NZ and around the world many of us are in lockdown and spending more 
time on our computers, if that were possible.  I have just completed the 
restoration of a PDP-8 Straight 8 which I believe is the only one in New 
Zealand.  You can view the restoration story and find appropriate resources 
here:  https://pdp-8.nz    

While it plays Chess, it would be great if someone wanted to write (say) a 
Prime Number Generator, or some other application and email it to me off list.  
I have Focal-69 and can probably source other languages for this wonderful old 
machine with 4K of memory.

--//
bren...@mcneill.co.nz
+64 21 881 883

Re: PDP-8 Straight 8 restoration

[Nigel Johnson via cctalk]

Brings back memories!  My first 6800 cross assembler came to me as 2000 
Fortran source code punch cards. We had an F4R4 compiler on the PDP11 
but the card reader was on the PDP-8.


The only common peripheral was paper tape.  One night, the Chief 
Engineer and I fed the cards into the PDP8 card reader, punched tape, 
and fed it directly into the PDP11 tape reader.  X-on X-off was handled 
by hitting the stop and continue buttons on the PDP8 as the punch was 
faster than the reader.  The buffer was a pile of paper tape in the 
floor, which we carefully prevented from tangling.  Somehow OS/8 managed 
to not crash with the constant start/stop.


Nobody was more surprised than we were when the output compiled 
perfectly on the PDP11 and we made our first 6800 program - a ham 
repeater controller!


The Chief Engineer is still alive - I was at his 95th birthday last year 
and we often have fun talking about the good old days!


cheers,

Nigel Johnson


On 29/03/2020 16:59, Diane Bruce via cctalk wrote:

On Mon, Mar 30, 2020 at 09:47:51AM +1300, Brendan McNeill via cctech wrote:

Here in NZ and around the world many of us are in lockdown and spending more time on 
our computers, if that were possible.  I have just completed the restoration of a 
PDP-8 Straight 8 which I believe is the only one in New Zealand.  You can view the 
restoration story and find appropriate resources here:  https://pdp-8.nz 


While it plays Chess, it would be great if someone wanted to write (say) a 
Prime Number Generator, or some other application and email it to me off list.  
I have Focal-69 and can probably source other languages for this wonderful old 
machine with 4K of memory.

I have memories of keying in RIM and BIN. Long long time ago. I also learned
how to talk to the OS/8 file system so we could play morse code from a file
instead of a paper tape for our University club station. ;)


--//
bren...@mcneill.co.nz
+64 21 881 883





73 de VA3DB for those that care ;)


 


--
Nigel Johnson
MSc., MIEEE
VE3ID/G4AJQ/VA3MCU

Amateur Radio, the origin of the open-source concept!


You can reach me by voice on Skype:  TILBURY2591

If time travel ever will be possible, it already is. Ask me again yesterday

This e-mail is not and cannot, by its nature, be confidential. En route from me 
to you, it will pass across the public Internet, easily readable by any number 
of system administrators along the way.
   Nigel Johnson 


Please consider the environment when deciding if you really need to print this message

Split Ceramic Disk Capacitor

[Rob Jarratt via cctalk]

Since I am forced to stay at home more than I would like I though I would
check some more PSUs. One I wanted to check was the H7109-C from one of my
VAXstation 4000 VLC machines. I found a leaked capacitor and some other high
ESR ones, so I will replace those. However, I also noticed a ceramic disk
capacitor that appears to be split all around the edge. Is that a known
failure mode?

 

Regards

 

Rob

Re: PDP-8 Straight 8 restoration

[Diane Bruce via cctalk]

On Sun, Mar 29, 2020 at 05:59:42PM -0400, Nigel Johnson via cctalk wrote:
> Brings back memories!  My first 6800 cross assembler came to me as 2000
> Fortran source code punch cards. We had an F4R4 compiler on the PDP11 but
> the card reader was on the PDP-8.

Funny how the kids don't realise Fortran was the 'C' language at one time.
Editors, linker, macro preprocessors a lot of it was done in Fortran. ;)

> 
> The only common peripheral was paper tape.  One night, the Chief Engineer
> and I fed the cards into the PDP8 card reader, punched tape, and fed it
> directly into the PDP11 tape reader.  X-on X-off was handled by hitting the
> stop and continue buttons on the PDP8 as the punch was faster than the
> reader.  The buffer was a pile of paper tape in the floor, which we
> carefully prevented from tangling.  Somehow OS/8 managed to not crash with
> the constant start/stop.

heh I can only imagine.

> 
> Nobody was more surprised than we were when the output compiled perfectly on
> the PDP11 and we made our first 6800 program - a ham repeater controller!

Cool!

> 
> The Chief Engineer is still alive - I was at his 95th birthday last year and
> we often have fun talking about the good old days!

Nice!


> 
> cheers,
> 
> Nigel Johnson
> 
> 
> On 29/03/2020 16:59, Diane Bruce via cctalk wrote:
> > On Mon, Mar 30, 2020 at 09:47:51AM +1300, Brendan McNeill via cctech wrote:
> > > Here in NZ and around the world many of us are in lockdown and spending 
> > > more time on our computers, if that were possible.  I have just completed 
> > > the restoration of a PDP-8 Straight 8 which I believe is the only one in 
> > > New Zealand.  You can view the restoration story and find appropriate 
> > > resources here:  https://pdp-8.nz 
> > > 
> > > While it plays Chess, it would be great if someone wanted to write (say) 
> > > a Prime Number Generator, or some other application and email it to me 
> > > off list.  I have Focal-69 and can probably source other languages for 
> > > this wonderful old machine with 4K of memory.
> > I have memories of keying in RIM and BIN. Long long time ago. I also learned
> > how to talk to the OS/8 file system so we could play morse code from a file
> > instead of a paper tape for our University club station. ;)
> > 
> > > --//
> > > bren...@mcneill.co.nz
> > > +64 21 881 883
> > > 
> > > 
> > > 
> > > 
> > 73 de VA3DB for those that care ;)
> 
> 
> -- 
> Nigel Johnson
> MSc., MIEEE
> VE3ID/G4AJQ/VA3MCU
> 
> Amateur Radio, the origin of the open-source concept!
> 
> 
> You can reach me by voice on Skype:  TILBURY2591
> 
> If time travel ever will be possible, it already is. Ask me again yesterday
> 
> This e-mail is not and cannot, by its nature, be confidential. En route from 
> me to you, it will pass across the public Internet, easily readable by any 
> number of system administrators along the way.
>Nigel Johnson 
> 
> Please consider the environment when deciding if you really need to print 
> this message
> 
> 

-- 
- d...@freebsd.org d...@db.net http://www.db.net/~db

Re: PDP-8 Straight 8 restoration

[Randy Dawson via cctalk]

I can't be the only one who would like to see the FORTRAN source of some of 
those editors, linkers, macro processors.

As a medical electronics guy, I had to deal with a fortran monster of a 
database engine, manman.

It was legacy in with the FDA, but woa, what a suck piece of crap it is.

Hi Diane.  Still Cadence here, signal integrity work for space


From: cctalk  on behalf of Diane Bruce via 
cctalk 
Sent: Sunday, March 29, 2020 4:09 PM
To: Nigel Johnson ; General Discussion: On-Topic and 
Off-Topic Posts 
Subject: Re: PDP-8 Straight 8 restoration

On Sun, Mar 29, 2020 at 05:59:42PM -0400, Nigel Johnson via cctalk wrote:
> Brings back memories!  My first 6800 cross assembler came to me as 2000
> Fortran source code punch cards. We had an F4R4 compiler on the PDP11 but
> the card reader was on the PDP-8.

Funny how the kids don't realise Fortran was the 'C' language at one time.
Editors, linker, macro preprocessors a lot of it was done in Fortran. ;)

>
> The only common peripheral was paper tape.  One night, the Chief Engineer
> and I fed the cards into the PDP8 card reader, punched tape, and fed it
> directly into the PDP11 tape reader.  X-on X-off was handled by hitting the
> stop and continue buttons on the PDP8 as the punch was faster than the
> reader.  The buffer was a pile of paper tape in the floor, which we
> carefully prevented from tangling.  Somehow OS/8 managed to not crash with
> the constant start/stop.

heh I can only imagine.

>
> Nobody was more surprised than we were when the output compiled perfectly on
> the PDP11 and we made our first 6800 program - a ham repeater controller!

Cool!

>
> The Chief Engineer is still alive - I was at his 95th birthday last year and
> we often have fun talking about the good old days!

Nice!


>
> cheers,
>
> Nigel Johnson
>
>
> On 29/03/2020 16:59, Diane Bruce via cctalk wrote:
> > On Mon, Mar 30, 2020 at 09:47:51AM +1300, Brendan McNeill via cctech wrote:
> > > Here in NZ and around the world many of us are in lockdown and spending 
> > > more time on our computers, if that were possible.  I have just completed 
> > > the restoration of a PDP-8 Straight 8 which I believe is the only one in 
> > > New Zealand.  You can view the restoration story and find appropriate 
> > > resources here:  https://pdp-8.nz 
> > >
> > > While it plays Chess, it would be great if someone wanted to write (say) 
> > > a Prime Number Generator, or some other application and email it to me 
> > > off list.  I have Focal-69 and can probably source other languages for 
> > > this wonderful old machine with 4K of memory.
> > I have memories of keying in RIM and BIN. Long long time ago. I also learned
> > how to talk to the OS/8 file system so we could play morse code from a file
> > instead of a paper tape for our University club station. ;)
> >
> > > --//
> > > bren...@mcneill.co.nz
> > > +64 21 881 883
> > >
> > >
> > >
> > >
> > 73 de VA3DB for those that care ;)
>
>
> --
> Nigel Johnson
> MSc., MIEEE
> VE3ID/G4AJQ/VA3MCU
>
> Amateur Radio, the origin of the open-source concept!
>
>
> You can reach me by voice on Skype:  TILBURY2591
>
> If time travel ever will be possible, it already is. Ask me again yesterday
>
> This e-mail is not and cannot, by its nature, be confidential. En route from 
> me to you, it will pass across the public Internet, easily readable by any 
> number of system administrators along the way.
>Nigel Johnson 
>
> Please consider the environment when deciding if you really need to print 
> this message
>
>

--
- d...@freebsd.org d...@db.net http://www.db.net/~db

Re: PDP-8 Straight 8 restoration

[Warner Losh via cctalk]

On Sun, Mar 29, 2020, 5:10 PM Diane Bruce via cctalk 
wrote:

> On Sun, Mar 29, 2020 at 05:59:42PM -0400, Nigel Johnson via cctalk wrote:
> > Brings back memories!  My first 6800 cross assembler came to me as 2000
> > Fortran source code punch cards. We had an F4R4 compiler on the PDP11 but
> > the card reader was on the PDP-8.
>
> Funny how the kids don't realise Fortran was the 'C' language at one time.
> Editors, linker, macro preprocessors a lot of it was done in Fortran. ;)
>

He was lucky the card deck was in order. One of my first jobs was to read
in old, horrible FORTRAN IV from punch card, then check it against a
listing the boss had and edit to match... This was the same place we wrote
malloc for FORTRAN and passed around all kinds of crazy data structures
that offset into the malloc arena so it would run on both the pdp-11 and
the vax...

Warner

>
> > The only common peripheral was paper tape.  One night, the Chief Engineer
> > and I fed the cards into the PDP8 card reader, punched tape, and fed it
> > directly into the PDP11 tape reader.  X-on X-off was handled by hitting
> the
> > stop and continue buttons on the PDP8 as the punch was faster than the
> > reader.  The buffer was a pile of paper tape in the floor, which we
> > carefully prevented from tangling.  Somehow OS/8 managed to not crash
> with
> > the constant start/stop.
>
> heh I can only imagine.
>
> >
> > Nobody was more surprised than we were when the output compiled
> perfectly on
> > the PDP11 and we made our first 6800 program - a ham repeater controller!
>
> Cool!
>
> >
> > The Chief Engineer is still alive - I was at his 95th birthday last year
> and
> > we often have fun talking about the good old days!
>
> Nice!
>
>
> >
> > cheers,
> >
> > Nigel Johnson
> >
> >
> > On 29/03/2020 16:59, Diane Bruce via cctalk wrote:
> > > On Mon, Mar 30, 2020 at 09:47:51AM +1300, Brendan McNeill via cctech
> wrote:
> > > > Here in NZ and around the world many of us are in lockdown and
> spending more time on our computers, if that were possible.  I have just
> completed the restoration of a PDP-8 Straight 8 which I believe is the only
> one in New Zealand.  You can view the restoration story and find
> appropriate resources here:  https://pdp-8.nz 
> > > >
> > > > While it plays Chess, it would be great if someone wanted to write
> (say) a Prime Number Generator, or some other application and email it to
> me off list.  I have Focal-69 and can probably source other languages for
> this wonderful old machine with 4K of memory.
> > > I have memories of keying in RIM and BIN. Long long time ago. I also
> learned
> > > how to talk to the OS/8 file system so we could play morse code from a
> file
> > > instead of a paper tape for our University club station. ;)
> > >
> > > > --//
> > > > bren...@mcneill.co.nz
> > > > +64 21 881 883
> > > >
> > > >
> > > >
> > > >
> > > 73 de VA3DB for those that care ;)
> >
> >
> > --
> > Nigel Johnson
> > MSc., MIEEE
> > VE3ID/G4AJQ/VA3MCU
> >
> > Amateur Radio, the origin of the open-source concept!
> >
> >
> > You can reach me by voice on Skype:  TILBURY2591
> >
> > If time travel ever will be possible, it already is. Ask me again
> yesterday
> >
> > This e-mail is not and cannot, by its nature, be confidential. En route
> from me to you, it will pass across the public Internet, easily readable by
> any number of system administrators along the way.
> >Nigel Johnson 
> >
> > Please consider the environment when deciding if you really need to
> print this message
> >
> >
>
> --
> - d...@freebsd.org d...@db.net http://www.db.net/~db
>

Re: Split Ceramic Disk Capacitor

[Peter Coghlan via cctalk]

>
> Since I am forced to stay at home more than I would like I though I would
> check some more PSUs. One I wanted to check was the H7109-C from one of my
> VAXstation 4000 VLC machines. I found a leaked capacitor and some other high
> ESR ones, so I will replace those. However, I also noticed a ceramic disk
> capacitor that appears to be split all around the edge. Is that a known
> failure mode?
>

Is it definately a capacitor?

I've had some damaged surge arrestors / MOVs / VDRs that look very similar
to ceramic disc capacitors.

Regards,
Peter Coghlan.

Re: PDP-8 Straight 8 restoration

[Marc Howard via cctalk]

Nigel,

I first learned assembly on a straight-8.  Also learned about repair with
the same machine (1974).

As for fun time wasters back then there was a DECUS paper tape that could
compute n! up to 200! exactly.  I remember that I could start it before
lunch, come back, and then about 15 minutes later it would start printing
all the digits for 200!.

Enjoy your 8,

Marc Howard


On Sun, Mar 29, 2020 at 2:59 PM Nigel Johnson via cctalk <
cctalk@classiccmp.org> wrote:

> Brings back memories!  My first 6800 cross assembler came to me as 2000
> Fortran source code punch cards. We had an F4R4 compiler on the PDP11
> but the card reader was on the PDP-8.
>
> The only common peripheral was paper tape.  One night, the Chief
> Engineer and I fed the cards into the PDP8 card reader, punched tape,
> and fed it directly into the PDP11 tape reader.  X-on X-off was handled
> by hitting the stop and continue buttons on the PDP8 as the punch was
> faster than the reader.  The buffer was a pile of paper tape in the
> floor, which we carefully prevented from tangling.  Somehow OS/8 managed
> to not crash with the constant start/stop.
>
> Nobody was more surprised than we were when the output compiled
> perfectly on the PDP11 and we made our first 6800 program - a ham
> repeater controller!
>
> The Chief Engineer is still alive - I was at his 95th birthday last year
> and we often have fun talking about the good old days!
>
> cheers,
>
> Nigel Johnson
>
>
> On 29/03/2020 16:59, Diane Bruce via cctalk wrote:
> > On Mon, Mar 30, 2020 at 09:47:51AM +1300, Brendan McNeill via cctech
> wrote:
> >> Here in NZ and around the world many of us are in lockdown and spending
> more time on our computers, if that were possible.  I have just completed
> the restoration of a PDP-8 Straight 8 which I believe is the only one in
> New Zealand.  You can view the restoration story and find appropriate
> resources here:  https://pdp-8.nz 
> >>
> >> While it plays Chess, it would be great if someone wanted to write
> (say) a Prime Number Generator, or some other application and email it to
> me off list.  I have Focal-69 and can probably source other languages for
> this wonderful old machine with 4K of memory.
> > I have memories of keying in RIM and BIN. Long long time ago. I also
> learned
> > how to talk to the OS/8 file system so we could play morse code from a
> file
> > instead of a paper tape for our University club station. ;)
> >
> >> --//
> >> bren...@mcneill.co.nz
> >> +64 21 881 883
> >>
> >>
> >>
> >>
> > 73 de VA3DB for those that care ;)
>
>
>
> --
> Nigel Johnson
> MSc., MIEEE
> VE3ID/G4AJQ/VA3MCU
>
> Amateur Radio, the origin of the open-source concept!
>
>
> You can reach me by voice on Skype:  TILBURY2591
>
> If time travel ever will be possible, it already is. Ask me again yesterday
>
> This e-mail is not and cannot, by its nature, be confidential. En route
> from me to you, it will pass across the public Internet, easily readable by
> any number of system administrators along the way.
> Nigel Johnson 
>
>
> Please consider the environment when deciding if you really need to print
> this message
>
>
>
>

RE: H7874 power supply

[Robert Armstrong via cctalk]

  Remembering that I have the R400x enclosure and I'm only interested in 
powering disk drives - I looked up the specs for the RF7x drives, and they all 
use about 1.5A at 5V and 2.5-3A operating at 12V.  There's a 5-6A spinup surge 
on the 12V supply, but as long as you spin them up in sequence you can probably 
gloss over that.  Anyway, I have 4xRF7x drives and two SCSI drives, so figure 
maybe 20A at 12V and 10A at 5V.  That's entirely doable with an ATX supply.  

  The fans, annoyingly, are 24VDC so those would either have to be replaced 
with 12V fans or I'd have to kludge up an extra 24V supply.

  My next step was to figure out the pinout of the connectors on the back of 
the H7874.  The big, high current, pins aren't marked anywhere inside the H7874 
that I could find but, conveniently, they ARE marked on the R400x backplane.  
There are also a couple of high density connectors sandwiched in between the 
power pins; the lower one doesn't appear to be used but the upper one has a few 
connections.  From looking at the backplane it appears that only four pins in 
the upper connector are actually connected.  That's a guess though, because I 
can't see that back side of the backplane.  

  I needed to see more of the backplane to figure out where these four 
connections went, so I removed all the drives from the R400x.  Then, on a whim, 
I stuck the H7874 back in there and tried to power it up.  It works!  It 
appears that I don't have a bad power supply after all; I have a bad drive 
somewhere.  Don't I feel silly :)

  So I don't need to fool with the ATX supply after all, or at least not until 
my PS really does die.  Thanks for the help, and sorry for the false alarm.

Bob


-Original Message-
From: Rob Jarratt [mailto:robert.jarr...@ntlworld.com] 
Sent: Sunday, March 29, 2020 2:05 PM
To: b...@jfcl.com; 'General Discussion: On-Topic Posts'; 'Maciej W. Rozycki'
Cc: r...@jarratt.me.uk
Subject: RE: H7874 power supply

I have some notes I made about trying a PC PSU, I don't think it really worked, 
there are signals to indicate power OK and perhaps others. But perhaps a more 
concerted effort might yield something that could work.

Regards

Rob

> -Original Message-
> From: cctech  On Behalf Of Robert
> Armstrong via cctech
> Sent: 29 March 2020 19:15
> To: 'Maciej W. Rozycki' ; 'General Discussion: On-
> Topic Posts' 
> Cc: r...@jarratt.me.uk
> Subject: RE: H7874 power supply
> 
> >Maciej W. Rozycki  wrote:
> >numerous Chemi-Con SXF parts scattered across all boards, some leaking
> 
>   Yeah, mine is full of "Nippon Chemi-Con" electrolytic too.
> 
>   What about just gutting the PS chassis and sticking in an ATX power supply? 
>  I
> don't know how the maximum current per output breaks down, but as I
> understand it the H7874 is only a 600W supply.  That's not a problem for an
> ATX supply, and it would have all the required output voltages.  You'd have to
> run the cabinet fans at a fixed speed and you'd lose the power control bus
> feature, but that's not a show stopper.
> 
>   Actually my unit is in an R400x chassis full of RF drives, so I believe I 
> only need
> +12 and +5.  I don't think the 3.3v and -12 are used in that case.  I wonder 
> how
> much current I really need for the drives?  I should look that up and I might 
> be
> able to find a surplus dual output supply that would do the job.
> 
> Thanks again,
> Bob

Re: PDP-8 Straight 8 restoration

[Richard Pope via cctalk]

Diane,
Very nicely done. I read the whole thing.
GOD Bless and Thanks,
rich!

On 3/29/2020 3:59 PM, Diane Bruce via cctech wrote:

On Mon, Mar 30, 2020 at 09:47:51AM +1300, Brendan McNeill via cctech wrote:

Here in NZ and around the world many of us are in lockdown and spending more time on 
our computers, if that were possible.  I have just completed the restoration of a 
PDP-8 Straight 8 which I believe is the only one in New Zealand.  You can view the 
restoration story and find appropriate resources here:  https://pdp-8.nz 


While it plays Chess, it would be great if someone wanted to write (say) a 
Prime Number Generator, or some other application and email it to me off list.  
I have Focal-69 and can probably source other languages for this wonderful old 
machine with 4K of memory.

I have memories of keying in RIM and BIN. Long long time ago. I also learned
how to talk to the OS/8 file system so we could play morse code from a file
instead of a paper tape for our University club station. ;)


--//
bren...@mcneill.co.nz
+64 21 881 883





73 de VA3DB for those that care ;)

Re: help needed: Document scan of ISS Sperry Univac Driver Exerciser avalaible for bitsavers upload

[ED SHARPE via cctalk]

which  iss  drive  the  10 plotter  20 meg one?   Ed#
In a message dated 3/27/2020 5:12:08 AM US Mountain Standard Time, 
cctalk@classiccmp.org writes:

On 3/27/20 3:55 AM, P Gebhardt via cctalk wrote:
> I contacted two times Al via email for access credentials to upload the 
> document as I did in the past years for numerous scans, but I never got an 
> answer.

private msg sent
sorry, things have been crazy

RE: Split Ceramic Disk Capacitor

[Rob Jarratt via cctalk]

I don't know, but thanks for pointing out that it might not be a capacitor.
I have two more VLCs so I will open them up and see what the markings are,
the markings on this one are almost illegible.

Thanks

Rob

> -Original Message-
> From: cctalk  On Behalf Of Peter Coghlan
via
> cctalk
> Sent: 30 March 2020 00:56
> To: General Discussion: On-Topic and Off-Topic Posts

> Subject: Re: Split Ceramic Disk Capacitor
> 
> >
> > Since I am forced to stay at home more than I would like I though I
> > would check some more PSUs. One I wanted to check was the H7109-C from
> > one of my VAXstation 4000 VLC machines. I found a leaked capacitor and
> > some other high ESR ones, so I will replace those. However, I also
> > noticed a ceramic disk capacitor that appears to be split all around
> > the edge. Is that a known failure mode?
> >
> 
> Is it definately a capacitor?
> 
> I've had some damaged surge arrestors / MOVs / VDRs that look very similar
to
> ceramic disc capacitors.
> 
> Regards,
> Peter Coghlan.

Re: help needed: Document scan of ISS Sperry Univac Driver Exerciser avalaible for bitsavers upload

[ED SHARPE via cctalk]

  I mean 
 which  iss  drive  the  10 platter pack.  the  20 meg one?   Ed# 




In a message dated 3/29/2020 10:22:30 PM US Mountain Standard Time, 
cctalk@classiccmp.org writes:

which  iss  drive  the  10 plotter  20 meg one?   Ed#
In a message dated 3/27/2020 5:12:08 AM US Mountain Standard Time, 
cctalk@classiccmp.org writes:

On 3/27/20 3:55 AM, P Gebhardt via cctalk wrote:
> I contacted two times Al via email for access credentials to upload the 
> document as I did in the past years for numerous scans, but I never got an 
> answer.

private msg sent
sorry, things have been crazy