> -Original Message-
> From: Paul Flo Williams via cctalk
> Sent: 05 February 2024 16:24
> To: cctalk@classiccmp.org
> Cc: Paul Flo Williams
> Subject: [cctalk] Re: vt220 firmware source?
>
> On Sun, 04 Feb 2024 16:26:57 -0700
> Richard via cctalk wrote:
>
> > In article you
> >
> -Original Message-
> From: Paul Koning
> Sent: 05 January 2024 00:34
> To: r...@jarratt.me.uk; cctalk@classiccmp.org
> Cc: Robert Jarratt
> Subject: Re: [cctalk] RIP: Software design pioneer and Pascal creator
Niklaus
> Wirth
>
>
>
> > On Jan
Sad news but a great article Liam, thanks for the interesting history.
The second language I taught myself was Algol 68 (!), on a DECSYSTEM20. I
learned Pascal at University, when I did my M.Sc I used VAX Pascal on a VAX
11/780 and went on to use it as my first professional language. I loved
I think I have got my VT100 basically working now except for the actual
video display. I think there is a problem with the transistor that drives
the flyback transformer. This is Q414 on page 58 of the Feb82 schematic on
BitSavers
> -Original Message-
> From: Christian Corti via cctalk
> Sent: 30 November 2023 08:43
> To: Rob Jarratt via cctalk
> Cc: Christian Corti
> Subject: [cctalk] Re: VT100 Monitor Board
>
> On Wed, 29 Nov 2023, 'General Discussion: On-Topic and Off-Topic Posts'
&
> -Original Message-
> From: Tony Duell
> Sent: 26 November 2023 06:35
> To: r...@jarratt.me.uk
> Cc: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: [cctalk] VT100 Monitor Board
>
> On Sat, Nov 25, 2023 at 11:12 PM Rob Jarratt
> wrote:
>
> > > Have you checked the
> -Original Message-
> From: Tony Duell
> Sent: 25 November 2023 14:17
> To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
>
> Cc: Rob Jarratt
> Subject: Re: [cctalk] VT100 Monitor Board
>
> On Sat, Nov 25, 2023 at 12:07 PM Rob
> -Original Message-
> From: Dave Dunfield via cctalk
> Sent: 25 November 2023 14:06
> To: cctalk@classiccmp.org
> Cc: Dave Dunfield <1297.dunfi...@gmail.com>
> Subject: [cctalk] Re: VT100 Monitor Board
>
> > Rob Jarratt 25 Nov 2023 8:47 a.m.
> > Of course the worry is, why? There
Hello,
As some may recall I have been working on getting a VT100 going again. I
have made good progress and I think the main board is probably OK now (see
here if you are interested:
https://robs-old-computers.com/2023/11/19/vt100-keyboard-constant-clicking-f
ault/). Possibly I still need to
long.
On Sun, Oct 8, 2023 at 9:35 AM Rob Jarratt via cctalk mailto:cctalk@classiccmp.org> > wrote:
> -Original Message-
> From: wrco...@wrcooke.net <mailto:wrco...@wrcooke.net> <mailto:wrco...@wrcooke.net> >
> Sent: 08 October 2023 04:15
> To: r...@j
> -Original Message-
> From: wrco...@wrcooke.net
> Sent: 08 October 2023 04:15
> To: r...@jarratt.me.uk; Rob Jarratt via cctalk
> Subject: Re: [cctalk] VT100: Failing 2114 Chip Replaced With One With The
> Same Fault
>
>
>
> > On 10/07/2023 5
I posted recently that I had identified a faulty RAM chip in my VT100 and
having replaced it the terminal seemed to get further into the self test.
After further analysis with the logic analyser I have realised that it is
still failing the RAM test, despite an apparent change in behaviour. I think
I have my faulty VT100 now passing the RAM test, but it is still not
producing any output to the screen. Looking at the DC012 chip it seems to be
permanently asserting the interrupt line and not generating any DMA HOLD
REQUEST signals. It seems that all the clock inputs are running (DOT CLK,
CHAR
I have a non-functioning VT100. I think it is failing in the POST during the
RAM check. I don't know for sure because I can't get it to light up the LEDs
on the keyboard, however I used my logic analyser (a HP1630G) to see what
values were written to the UART to send to the keyboard and I see it
level above or below the signal.
5) Trigger mode set to "Auto" as opposed to "Normal" or "Single" causing a
momentary display of the triggered signal which is immediately overwritten by
the current signal.
Tom Hunter
On Mon, Jul 17, 2023 at 1:14 AM Rob Ja
gh and the low WR pulse comes
> along.
> > It's both status and timing, coming out of the 8228.
> >
> > You would probably do well seeing if MEMR and MEMW are asserting. If
> > the program is running off due to e.g. bad RAM, ROM bitrot, etc. you
> > may never see the I/O
ll me exactly how it works. It isn't completely clear to me if it
> > needs HLDA to be asserted for I/O W to be asserted.
> >
> > > -Original Message-
> > > From: Rob Jarratt via cctalk cctalk@classiccmp.org
> > > Sent: Sunday, July 9, 2023 4:39 PM
> &
m: Rob Jarratt via cctalk
> Sent: Sunday, July 9, 2023 4:39 PM
> To: General Discussion: On-Topic and Off-Topic Posts
>
> Cc: Rob Jarratt
> Subject: [cctalk] VT100: Datasheet for Intel 8228
>
> Hello,
>
>
>
> I have a non-functioning VT100. I think I may have
Hello,
I have a non-functioning VT100. I think I may have isolated the problem to
an Intel 8228 chip (or 88228, the schematic says 8228, the part is marked
88228C). Certainly, the part gets a bit hot and it doesn't seem to be
outputting anything on the I/O W pin (pin 27) despite activity on
Thank you to everyone who helped me with this. The PSU if finally fixed. I have
posted about it on my blog:
https://robs-old-computers.com/2023/06/29/h7842-finally-fixed/
Regards
Rob
> -Original Message-
> From: Rob Jarratt
> Sent: 25 June 2023 18:07
> To: 'Tony Duell' ;
> -Original Message-
> From: Tony Duell
> Sent: 25 June 2023 18:00
> To: r...@jarratt.me.uk
> Cc: General Discussion: On-Topic and Off-Topic Posts
> ; Brent Hilpert
> Subject: Re: [cctalk] Re: Rainbow H7842 PSU Fault
>
> On Sun, Jun 25, 2023 at 5:52 PM Rob Jarratt
> wrote:
> >
> >
Yes the chopper did blow up and I have since replaced it. So hopefully this is
the last part that needs to be replaced!
Regards
Rob
> -Original Message-
> From: Tony Duell
> Sent: 25 June 2023 17:52
> To: r...@jarratt.me.uk
> Cc: General Discussion: On-Topic and Off-Topic Posts
> ;
nt: 25 June 2023 14:21
> > To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic
> > Posts
> > Cc: Brent Hilpert ; Rob Jarratt
> >
> > Subject: Re: [cctalk] Re: Rainbow H7842 PSU Fault
> >
> > On Sun, Jun 25, 2023 at 1:36 PM R
nd Off-Topic Posts
>
> Cc: Brent Hilpert ; Rob Jarratt
>
> Subject: Re: [cctalk] Re: Rainbow H7842 PSU Fault
>
> On Sun, Jun 25, 2023 at 1:36 PM Rob Jarratt via cctalk
> wrote:
> >
> > Hello,
> >
> > It has taken me ages to get back to this, but I
> -Original Message-
> From: Jon Elson via cctalk
> Sent: 25 June 2023 16:24
> To: Rob Jarratt via cctalk
> Cc: Jon Elson
> Subject: [cctalk] Re: Rainbow H7842 PSU Fault
>
> On 6/25/23 07:36, Rob Jarratt via cctalk wrote:
> > This made me suspect th
Rob
> -Original Message-
> From: Brent Hilpert
> Sent: 26 May 2023 17:24
> To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
>
> Subject: Re: [cctalk] Rainbow H7842 PSU Fault
>
> On 2023-May-25, at 1:43 PM, Rob Jarratt via cctalk wrote:
>
> -Original Message-
> From: Peter Coghlan via cctalk
> Sent: 20 May 2023 09:20
> To: 'General Discussion: On-Topic and Off-Topic Posts'
>
> Cc: Peter Coghlan
> Subject: [cctalk] Re: Rainbow H7842 PSU Fault
>
>
>
> Ok, it looks like there is not a severe leak from the -12V line to
> -Original Message-
> From: Peter Coghlan via cctalk
> Sent: 10 May 2023 12:04
> To: 'General Discussion: On-Topic and Off-Topic Posts'
>
> Cc: Peter Coghlan
> Subject: [cctalk] Re: Rainbow H7842 PSU Fault
>
>
> >
> > I will do all the suggested checks, but I won't be able to do
> -Original Message-
> From: Peter Coghlan via cctalk
> Sent: 09 May 2023 17:58
> To: 'General Discussion: On-Topic and Off-Topic Posts'
>
> Cc: Peter Coghlan
> Subject: [cctalk] Re: Rainbow H7842 PSU Fault
>
> >
> > I am going to read your answer more carefully later. But I wanted
>
> I don't think we can draw any conclusions from voltage measurements
> around the TIP121 without the -12V line being approximately correct or at
> the very least being negative.
>
> It's collector voltage being 0V on the good PSU suggests there is no current
> flowing through the parallel 20R
> -Original Message-
> From: Peter Coghlan via cctalk
> Sent: 07 May 2023 10:34
> To: General Discussion: On-Topic and Off-Topic Posts
>
> Cc: Peter Coghlan
> Subject: [cctalk] Re: Rainbow H7842 PSU Fault
>
> >
> > The comments about the tolerance of the 7812 were right, it doesn’t
> -Original Message-
> From: Brent Hilpert
> Sent: 07 May 2023 23:53
> To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
>
> Subject: Re: [cctalk] Rainbow H7842 PSU Fault
>
> On 2023-May-07, at 1:54 AM, Rob Jarratt via cctalk wrote
The comments about the tolerance of the 7812 were right, it doesn’t appear to
be an issue with the replacement 7812 regulator because when I tried using the
bench PSU to feed exactly 12V to the circuit from the output of the 7812 the
comparator still gave the wrong result. It was still wrong if
That’s a good idea, I will try that
From: Mattis Lind
Sent: Tuesday, May 2, 2023 7:55 AM
To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
Cc: Rob Jarratt
Subject: Re: [cctalk] Re: Rainbow H7842 PSU Fault
Not quite sure what you mean here. I had advice
> -Original Message-
> From: Brent Hilpert via cctalk
> Sent: Monday, May 1, 2023 11:23 PM
> To: General Discussion: On-Topic and Off-Topic Posts
>
> Cc: Brent Hilpert
> Subject: [cctalk] Re: Rainbow H7842 PSU Fault
>
> On 2023-May-01, at 2:25 AM, Peter Coghlan via cctalk wrote:
> >
7812 shows 2 versions - 4% and 2% tolerances. So
> > > the
> > voltages your measuring are within the 4% part. Maybe you do need the
> > 2% one.
> > >
> > > Sent from my iPhone
> > >
> > >> On Apr 30, 2023, at 11:26, Rob Jarratt via cctalk
4% and 2% tolerances. So the
> voltages your measuring are within the 4% part. Maybe you do need the 2%
> one.
> >
> > Sent from my iPhone
> >
> >> On Apr 30, 2023, at 11:26, Rob Jarratt via cctalk
> wrote:
> >>
> >> I think I have foun
I think I have found a possible cause, but not too sure what to do about it
if I have.
I had to replace the 7812 regulator that supplies Vstart. The new one has an
output that seems to vary between 12.2 and 12.4V. The 7812 on the good PSU
outputs a steady 12.1V. I think that is enough to cause
> It looks like the conditions in the control and overcurrent sensing parts
of the
> working and the non-working PSUs are different so some further
investigation
> may be required as to why this is the case.
>
Yes, that is certainly the problem. Presumably more current is flowing
through the
Thanks for the various replies. Here are my responses and further
observations.
I was asked if I had a load on the PSU while bench testing it. The answer to
that is no.
I did check the two diodes around the -12V current sensing resistor (PSU
Sheet 3), but as was pointed out the current sensing
As some of you may be aware I am trying to find a fault in a Rainbow H7842
PSU. I am using Tony Duell's schematic from here
http://www.bitsavers.org/pdf/dec/rainbow/duell_schematics/psu.pdf.
I have been testing the Control Module by using a bench PSU to supply 15VDC
to the input of the 7812
I wouldn't mind having a copy for completeness too...
> -Original Message-
> From: Hans-Ulrich Hölscher via cctalk
> Sent: 17 March 2023 13:25
> To: General Discussion: On-Topic and Off-Topic Posts
> Cc: Plamen Mihaylov ; Hans-Ulrich
> Hölscher
> Subject: [cctalk] Re: VMS V4.2 MUP
I have done a little more probing around. I have found that the 7812 regulator
that drives Vstart on sheet 1 of Tony Duell’s schematic is shorted, so I will
have to replace this too. I have not found anything else that looks obviously
suspicious. I can’t test the output rectifiers for shorts
> -Original Message-
> From: Will Cooke via cctalk
> Sent: 26 November 2022 19:12
> To: Rob Jarratt via cctalk
> Cc: wrco...@wrcooke.net
> Subject: [cctalk] Re: Identifying a Failed Diode in a Rainbow H7842 Power
> Supply
>
>
> I'm not at all familiar w
Just trying to decide what to replace the failed diode with, and looking at the
UF400x series, as suggested by Mattis. It seems to me that as long as the PIV
is 200V or higher it should be fine from that point of view, the switching
speed is never higher than 70ns, while the original A114x
Tony Duell has reverse engineered the following schematic.
http://www.bitsavers.org/pdf/dec/rainbow/duell_schematics/psu.pdf
I will go with the 1000V as you suggest anyway.
Thanks
Rob
From: Mattis Lind
Sent: 25 November 2022 07:12
To: r...@jarratt.me.uk
Cc: General
Thanks for the suggestion Mattis. The UF4007 has a PIV of 1000V, I had a
suggestion that the PIV should be 200V. Not sure what rating I should be going
for here?
Regards
Rob
From: Mattis Lind
Sent: 22 November 2022 07:54
To: r...@jarratt.me.uk; General Discussion: On-Topic and
cctalk
> Sent: 20 November 2022 20:38
> To: Rob Jarratt via cctalk
> Cc: Antonio Carlini
> Subject: [cctalk] Re: Identifying a Failed Diode in a Rainbow H7842 Power
> Supply
>
> On 20/11/2022 17:40, Rob Jarratt via cctalk wrote:
> > The H7842 PSU in my Rainbow failed yesterd
Hello Peter,
Thanks for the analysis. There doesn't seem to be anything further back from
the diode, unless you mean further back behind the inductor?
I will check on the output side as you suggest.
The circuit breaker did pop out when it failed. The onboard fuse is intact.
The house RCD
The H7842 PSU in my Rainbow failed yesterday. At first the machine just
powered down and there was a slight burning smell, I wasn't next to the
machine when this happened, so I didn't see or hear anything to tell me
where the problem might be. Not being sure if there was a short in the
machine or
Given all the troubles I have had with the H7140 in my PDP 11/24 I am
considering whether to replace it with modern equivalents, installed inside
the H7140 enclosure. I am a bit puzzled by the specs listed in the PDP 11/24
Maintenance Card, it suggests the PSU outputs +12V and -12V from the memory
I have a HP-150 but I am in the UK. I think it would be good to get the images
made and archived before sending the floppies anywhere at all.
Regards
Rob
> -Original Message-
> From: Stan Sieler via cctalk
> Sent: 07 September 2022 01:51
> To: ba...@googlegroups.com; General
I have just worked out how to dismantle the keycaps, although still
wondering if cleaning them will actually help?
> -Original Message-
> From: Rob Jarratt via cctalk
> Sent: 29 August 2022 11:26
> To: General Discussion: On-Topic and Off-Topic Posts
>
> Cc: Rob
I have a nice HP1630G logic analyser. It still works OK but has a number of
issues that I would like to fix.
First, I managed to break the power switch. It became stiff and wouldn't
readily toggle the power. I think the shaft became bent. In pressing too
hard, I broke off the button on the end
The 11/24 System Technical Manual says that the terminator (M9302 or M9312)
must be installed in the last slot (slot 9) of the backplane, and that all
empty slots must have a grant card. What I am not clear on is what they mean
by an "empty" slot. Specifically, if I have the CPU, the M7134 memory
I am trying to work out why my PDP 11/24 CPU is not working. To do so I want
to use my logic analyser on the F-11 chips. I have a regular 40-pin test
clip, but it doesn't make a good contact with the pins on the F-11 chips.
The test clips I have are made for regular DIP chips where the legs come
Murphy
Subject: Re: Replacement for a DEC 7474 Chip
On May 16, 2022, at 4:59 PM, Rob Jarratt via cctalk mailto:cctalk@classiccmp.org> > wrote:
I have several 7474s, including one marked DEC 7474. Sadly, I fear that
shipping from the US is likely to be prohibitive.
I have o
> -Original Message-
> From: cctalk On Behalf Of Rick Murphy via
> cctalk
> Sent: 16 May 2022 17:28
> To: cctalk@classiccmp.org
> Subject: Re: Replacement for a DEC 7474 Chip
>
> On 5/15/2022 4:16 AM, Eric Smith via cctalk wrote:
> > On Sat, May 14, 2022, 16:09 ben via cctalk wrote:
,
> the origin of the open-source concept!
> Skype: TILBURY2591
>
>
> On 2022-05-14 13:48, Paul Koning via cctalk wrote:
> >
> >> On May 14, 2022, at 1:41 PM, John Robertson via
> cctalk wrote:
> >>
> >> On 2022/05/14 10:11 a.m., Rob Jarratt v
Hello,
I have found a bad DEC 7474 chip on my M7133 board. Clearly it is a
7474 D flip flop. The problem is I don't know which modern series
would be the best one to replace it with. I am sure I have seen a list
somewhere of modern equivalents for some DEC chip numbers, but I can't
remember
I am embarrassed to report that after trying all the suggestions etc, I then
realised that I had connected the enable signal to pin 9 and not 19. I knew
it was 19, I knew where 19 was, but for some unfathomable reason I connected
it to 9 instead, despite checking multiple times. The original chip
> -Original Message-
> From: cctalk On Behalf Of Chris Zach via
> cctalk
> Sent: 01 May 2022 02:57
> To: CCTalk mailing list
> Subject: Repairing a VT240.
>
> So I'm clearing out projects on my bench. The latest is a Dec VT240 which did
> not work. Has been dead for 20 years, the
In trying to fix my M7133 CPU from my 11/24 I thought I had identified a
failed 74S240. However, when I replaced it (while adding a socket), the
fault remained. So, I guess the original chip may not be faulty. I decided
to test the original chip on a breadboard to see if it is OK. This is where
I
ansfer! Clean tip and a quick touch with solder is all that is needed.
> When you are not using the iron for some time, but leaving it on, add a
> thicker blob of solder on it so it doesn't get a thin hard to clean oxide on
> it.
> KEEP YOUR TIP FREE OF THIN OXIDE!
> Dwight
>
>
&
; Rob Jarratt ; General
Discussion: On-Topic and Off-Topic Posts ; Rob Jarratt
via cctalk
Subject: Re: Advice on Desoldering an IC
Cut the pins with a very sharp set of dykes then remove them one at a time.
Then use flux and detailer braid to remove the solder
On April 15, 2022 1:49:33 PM EDT
I am trying to remove an IC from my PDP 11/24 CPU, a DS8641. I am really
struggling to desolder it. I am using the technique of applying fresh solder
and then removing it. But after multiple cycles of this I think I am
starting to damage the PCB.
I am using a fairly cheap desoldering station
> -Original Message-
> From: cctalk On Behalf Of Noel Chiappa via
> cctalk
> Sent: 03 April 2022 03:41
> To: cctalk@classiccmp.org
> Cc: j...@mercury.lcs.mit.edu
> Subject: RE: PDP 11/24 - A Step Backwards
>
> > It was quite a struggle to separate those nylon connectors, is there
> -Original Message-
> From: cctalk On Behalf Of Rob Jarratt via
> cctalk
> Sent: 02 April 2022 11:58
> To: 'Noel Chiappa' ; 'General Discussion:
On-Topic
> and Off-Topic Posts'
> Subject: RE: PDP 11/24 - A Step Backwards
>
> >
> > Disconnec
> -Original Message-
> From: Brent Hilpert
> Sent: 31 March 2022 22:48
> To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
>
> Subject: Re: PDP 11/24 - A Step Backwards
>
> On 2022-Mar-31, at 2:14 PM, Rob Jarratt wrote:
> >> Those three comparators in the H777
>
> Disconnect the bad ACLO, power it on, and see if the CLK LED comes on. if
> not, then we'll have to work out why not.
This is my plan for later today.
>
> Noel
I made some interesting discoveries this evening. See below.
> -Original Message-
> From: cctalk On Behalf Of Brent Hilpert
via
> cctalk
> Sent: 31 March 2022 21:03
> To: General Discussion: On-Topic and Off-Topic Posts
>
> Subject: Re: PDP 11/24 - A Step Backwards
>
> On 2022-Mar-31,
> -Original Message-
> From: cctalk On Behalf Of Tony Duell via
> cctalk
> Sent: 31 March 2022 04:26
> To: Noel Chiappa ; General Discussion: On-Topic
> and Off-Topic Posts
> Subject: Re: PDP 11/24 - A Step Backwards
>
> On Thu, Mar 31, 2022 at 3:52 AM Noel Chiappa via cctalk
>
> -Original Message-
> From: Tony Duell
> Sent: 27 March 2022 10:15
> To: r...@jarratt.me.uk; Rob Jarratt ; General
> Discussion: On-Topic and Off-Topic Posts
> Subject: Re: PDP 11/24 - A Step Backwards
>
> On Sat, Mar 26, 2022 at 9:20 PM Rob Jarratt via cctalk
&g
cctalk On Behalf Of Matt Burke via
> cctalk
> Sent: 29 March 2022 01:31
> To: cctalk@classiccmp.org
> Subject: Re: PDP 11/24 - A Step Backwards
>
> On 28/03/2022 23:22, Rob Jarratt via cctalk wrote:
> > Its 600mV, but it is more of a spike than a ripple. Here is a trace:
> >
ssion: On-Topic and Off-Topic Posts
> Cc: Chris Zach
> Subject: Re: PDP 11/24 - A Step Backwards
>
> How bad is the ripple?
> Anyone on the list know what’s acceptable?
>
>
> Sent from my iPhone
>
> > On Mar 28, 2022, at 14:46, Rob Jarratt via cctalk
> -Original Message-
> From: cctalk On Behalf Of Chris Zach via
> cctalk
> Sent: 28 March 2022 20:57
> To: cctalk@classiccmp.org
> Subject: Re: PDP 11/24 - A Step Backwards
>
> > I don't think the CPU is working at all. The reason being that there
> > is absolutely no LED activity.
> -Original Message-
> From: cctalk On Behalf Of Antonio Carlini
> via cctalk
> Sent: 28 March 2022 07:50
> To: cctalk@classiccmp.org
> Subject: Re: PDP 11/24 - A Step Backwards
>
> On 28/03/2022 04:57, Tony Duell via cctalk wrote:
> >
> > Very little of the stuff I've bought new has
mpany called Radwell International. Based near me. They succeeded in
getting the PSU to work, which I have been unable to do as it is just beyond me.
>
> On 3/27/2022 2:38 PM, Bill Gunshannon via cctalk wrote:
> > On 3/27/22 05:17, Tony Duell via cctalk wrote:
> >> On Sat, Mar
Thanks for the lengthy reply. Some responses inline below.
> -Original Message-
> From: Noel Chiappa
> Sent: 27 March 2022 21:09
> To: cctalk@classiccmp.org
> Cc: j...@mercury.lcs.mit.edu
> Subject: RE: PDP 11/24 - A Step Backwards
>
> > From: Rob Jarratt
>
> > today I went
> -Original Message-
> From: cctalk On Behalf Of Toby Thain via
> cctalk
> Sent: 26 March 2022 22:07
> To: cctalk@classiccmp.org
> Subject: Re: PDP 11/24 - A Step Backwards
>
> On 2022-03-26 5:20 p.m., Rob Jarratt via cctalk wrote:
> > I had the H714
I had the H7140 PSU in my PDP 11/24 repaired a little while ago and I posted
about it here: https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/
I have since had the PSU fixed again and it came back a couple of weeks ago.
When I installed it and applied power to the input, I heard a
gt; you have
> > clearance at the bottom!).
> >
> > Regardless you shouldn't need to play with the slide-to-chassis
> > attachment points -- those are always "just so" and not really free to
> > fiddle with (no
> > "slop").
>
> There *is
> -Original Message-
> From: Paul Koning
> Sent: 26 February 2022 19:21
> To: r...@jarratt.me.uk; Robert Jarratt ;
> cctalk@classiccmp.org
> Subject: Re: Racking a PDP-11/24
>
>
>
> > On Feb 26, 2022, at 3:14 AM, Rob Jarratt via cctalk
> wro
hose are always "just so" and not really free to fiddle with
(no
> "slop").
There *is* a bit of play in the big black sheet that is screwed onto CPU
enclosure.
>
> In my experience "racking" is a fiddling-time and clearances can be
*really*
> tight. But
I am wondering if I have racked my 11/24 correctly.
As you can see here:
https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have put the
CPU at the top and the two RL02 drives underneath.
The problem is that the CPU enclosure catches on the RL02 underneath. There
is a bit of
If images don't exist would it be possible to image them and get them on
BitSavers?
> -Original Message-
> From: cctalk On Behalf Of Rod Smallwood
> via cctalk
> Sent: 24 February 2022 08:05
> To: Bill Gunshannon via cctalk
> Subject: 11/83 OS load - problem solved.
>
> Hi
>
>
I saw this reply later than the previous one. It confirms that I don't
*need* it for booting, but it would be useful.
I suspect some of the other cards that were in the machine might do the
necessary termination stuff.
Thanks
Rob
> -Original Message-
> From: cctalk On Behalf Of Noel
is less useful without at least a console ROM
Where are you located? Maybe someone nearby has in you could borrow just to
see what you need.
Bill.
On Sat, Feb 19, 2022, 2:12 AM Rob Jarratt via cctalk mailto:cctalk@classiccmp.org> > wrote:
I have a PDP-11/24. I have never got ve
I have a PDP-11/24. I have never got very far with it because of power
supply problems which I am hopeful will be resolved soon. Looking at the
technical manual, it describes an M9312 bootstrap/terminator module. The
machine did not come with one of these.
I am not sure how the machine could
I found a 400V part on Mouser and ordered that.
> -Original Message-
> From: Jonathan Chapman
> Sent: 18 February 2022 21:23
> To: r...@jarratt.me.uk; Rob Jarratt ; General
> Discussion: On-Topic and Off-Topic Posts
> Subject: RE: Testing H745 Regulators
>
> > I always forget that the
re may also be some
> dependance on how your bench PS responds in current limit.
>
But if that was the case shouldn't it just take a bit of time to get going,
once the input cap has charged wouldn't it start regulating? It shouldn't
take more than a few seconds, but it never see
ages/dec/pdp1110_psu_repair/rectifier_spac
> er.jpg
>
> Thanks,
> Jonathan
>
> --- Original Message ---
>
> On Thursday, February 17th, 2022 at 17:57, Rob Jarratt via cctalk
> wrote:
>
> > Hmmm this would suggest 200V 20A
> >
&g
r...@jarratt.me.uk; Rob Jarratt ;
> > General
> > Discussion: On-Topic and Off-Topic Posts
> > Subject: Re: Testing H745 Regulators
> >
> > On 2022-Jan-26, at 3:41 PM, Rob Jarratt via cctalk wrote:
> > > I am trying to test a couple of H745 regulators with a DC
3
> To: r...@jarratt.me.uk; Rob Jarratt ; General
> Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Testing H745 Regulators
>
> On 2022-Jan-26, at 3:41 PM, Rob Jarratt via cctalk wrote:
> > I am trying to test a couple of H745 regulators with a DC bench PSU
>
>
>
>
> -----Original Message-----
> From: cctalk On Behalf Of Rob Jarratt via
> cctalk
> Sent: Wednesday, January 26, 2022 6:42 PM
> To: General Discussion: On-Topic and Off-Topic Posts
>
> Subject: Testing H745 Regulators
>
> I am trying to tes
I am trying to test a couple of H745 regulators with a DC bench PSU and I am
having some problems with testing them.
My bench PSU is a twin unit so I can supply the +15V required as well as the
"AC" input using 20VDC from the other half of the bench PSU. The problem is
that I don't think the
I am going to be moving on to testing some H745 regulators. If I understand
the schematic correctly the +15V input is the reference voltage used to
regulate the -15V output, is that correct? If so, then presumably it doesn't
need a whole lot of current, is that right?
Thanks
Rob
>
> The hot tweezer sounds very nice but I think I'll stick with what I have
for
> now. These machines have other problems and won't ever do anything
> useful unless I get the cache issues sorted out so I don't necessarily
want to
> invest in new tools for them to end up not getting them
To make testing of the H744 a bit easier I would like to try to make up some
connectors for the mate-n-lok connector to make it easier to connect power
and load. I know the H744 uses a mate-n-lok connector, but there seem to be
a lot of different types and I don't seem to be able to find a type
Weirdly, the whine has disappeared. This is after I put the suspect capacitors
back in. Because I had previously removed them for reforming, I wonder if one
of them was not properly screwed in?
Regards
Rob
> -Original Message-
> From: cctalk On Behalf Of Jay Jaeger via
> cctalk
>
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