> From: "Rob Jarratt"
> I did plug the connector back in, so that DCLO and
> LTC are connected, I just removed the ACLO pin.
Ah, OK, good. Pulling the pins from those Mate-n-Loc shells without the right
tool is tricky; glad you did it, because as Brent Hilpert pointed out, having
a w
> The 'unused' gate in E52 is the one that the added wires from the ACLO
> ECO went to; I wonder if it was damaged by the -15V, somehow?
So, I checked, and the wire that goes from the plated-through hole next to the
etch cut on E70p1 winds up at E52p4 (the bus line on that transceiver),
th
On 4/2/2022 5:12 PM, Rob Jarratt via cctalk wrote:
Using tack soldered wires, I have traced back and I *think* I have found
something. There could be a fault in E52 (sheet K6, p157 of the PDF). While
K6 BUS DCLO L is +5V, I am measuring K6 BUF DCLO H at an average 1.64V with
50us spikes at 2.08V
> -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 th
> It was quite a struggle to separate those nylon connectors, is there a
> trick to it?
You mean the Mate-n-lok's? Not really; just make sure the catch is released.
What did you do about DCLO? (Oh, I think I see the answer, below looks
like you're relying on the pullup on K3...)
> -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
>
> >
> &
Finally found time to get to this one...
> From: Rob Jarratt
> However, there is a puzzle. On the CPU I found that the track from the
> pull up resistor to E70 has been cut.
I don't know about the "pull up resistor" part, but I have several KDF11-U's,
and _all_ of them have the trace
On 4/2/2022 5:49 AM, Noel Chiappa via cctalk wrote:
> does [disabling the MCLK counter via DCLO, asserted by the two
> E126 monostable chain from ACLO] happen just on power-down, or on
> power-up too? I'd need to understand how that two monostable chain
> works in both cases,
> -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:
> >> Th
> and there is some circuitry driving the clear input on the second
> 123.
Never mind this section. I mis-read the print; the clear input is connected to
an _input_ of the flop below (which is also tied high).
Noel
>
> 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
> does [disabling the MCLK counter via DCLO, asserted by the two
> E126 monostable chain from ACLO] happen just on power-down, or on
> power-up too? I'd need to understand how that two monostable chain
> works in both cases, which I currently don't. (I only understand
> monostab
> From: Brent Hilpert
>> ACLO is only used to trigger a 'power-failing' interrupt; CPU
>> operation is otherwise un-affected by ACLO (so the CPU can get ready).
>> DEC P/S's carefully sequence ACLO and DCLO such that on power-down,
>> ACLO is asserted first (to allow the CPU t
On 2022-Mar-31, at 7:44 PM, Noel Chiappa wrote:
>> From: Brent Hilpert
>> DCLO & ACLO behave as power-on-reset signals to the system.
>
> Minor nit: actually, I think it's DCLO which performs that function in a lot
> of places; see e.g. the latches on pg. K2 (pg. 153 of the PDF) and K7. (INIT,
> u
On Fri, Apr 1, 2022 at 12:13 AM Noel Chiappa via cctalk
wrote:
> > I really wish when people are asking for assistance or talking about a
> > schematic or circuit they would include a link/reference to exactly
> > what they are looking at
>
> But everone probably _was_ looking at the
> From: Brent Hilpert
> DCLO & ACLO behave as power-on-reset signals to the system.
Minor nit: actually, I think it's DCLO which performs that function in a lot
of places; see e.g. the latches on pg. K2 (pg. 153 of the PDF) and K7. (INIT,
usually in buffered form, is used more widely for
On 2022-Mar-31, at 4:12 PM, Noel Chiappa wrote:
>> From: Brent Hilpert
>
>> So apparently I've been looking at the wrong +5V supply (H777) because
>> the rest of you are indeed looking at a different +5 supply (H7140),
>> both of which are in that same 11/24 pdf document
>
> That's because the H7
> From: Brent Hilpert
> So apparently I've been looking at the wrong +5V supply (H777) because
> the rest of you are indeed looking at a different +5 supply (H7140),
> both of which are in that same 11/24 pdf document
That's because the H777 is the P/S for the BA11-L 5-1/4" box, a
On 2022-Mar-31, at 2:14 PM, Rob Jarratt wrote:
>> Those three comparators in the H777 are looking at a time-delay ramp
>
> Is that a typo? This is the H7140 not the H777.
Groan.
When this thread came up I went looking for the 11/24 schematic. I found the
document I linked earlier for the 11/24
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 Backward
On 2022-Mar-31, at 12:36 AM, Noel Chiappa via cctalk wrote:
>> From: Tony Duell
>
>> A short in FET Q15 on the bias/interface board in the PSU could do it.
>> The gate of that FET is driven from an LM339 comparator the -ve supply
>> of which is -15V.
>
> Ah; I hadn't even looked at the P/S prints
> From: Tony Duell
> A short in FET Q15 on the bias/interface board in the PSU could do it.
> The gate of that FET is driven from an LM339 comparator the -ve supply
> of which is -15V.
Ah; I hadn't even looked at the P/S prints.
(Like I said, I'm really weak on analog: for digita
> -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
On Thu, Mar 31, 2022 at 3:52 AM Noel Chiappa via cctalk
wrote:
> If the machine then runs, it's up to you as to whether you get the P/S
> repaired so that ACLO work properly - your call. (I wonder how the -15V got
> to ACLO - I suspect a solder bridge from the prior repair - but knowing the
> ans
> From: Rob Jarratt
> I found these two signals and ACLO is low (-15V)
'Good news, bad news'...
Bad is that something is seriously wrong there; 'allowed' values are 0v
(asserted) and +3V (un-asserted). I'm worried that the -15V will have taken
out some of the semiconductors that are 'lis
Rob
> -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 cctal
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:
>
> From: Brent Hilpert
> But the LED and CPU clock are not driven directly by that RC oscillator
> - there's a bunch of logic in-between the oscillator and the LED / CPU
> clock.
Oh, sure; it was late (for me; the dog woke me up at AM today :-), and it had
taken me a while to get e
On 3/29/2022 2:28 AM, Joshua Rice wrote:
Just to chip in my 5 pennies worth. At least in the QBUS world, the only
chipset that wouldn't ODT without memory is the original LSI-11 (and the
T11 i believe, but that's moot because they came with RAM onboard). You
should still get ODT on F11 and J
-- Original Message --
From: "Chris Zach via cctalk"
To: r...@jarratt.me.uk; "'General Discussion: On-Topic and Off-Topic
Posts'"
Sent: Tuesday, 29 Mar, 2022 At 00:11
Subject: Re: PDP 11/24 - A Step Backwards
I have been reluctant to put everything
On 2022-Mar-28, at 4:07 PM, Noel Chiappa via cctalk wrote:
>> I don't think the CPU is working at all. The reason being that there is
>> absolutely no LED activity. Including an LED that is supposed to indicate
>> a clock.
>
> Looking at the KDF11-U prints, I finally found that LED (it's pretty lo
On 3/28/22 21:55, Jon Elson wrote:
On 3/28/22 17:22, Rob Jarratt via cctalk wrote:
Its 600mV, but it is more of a spike than a ripple.
That's probably not real. It looks like noise pickup from
the probe ground lead. Try disconnecting the probe tip
and see if you still get similar signals.
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:
> https://rjarratt.files.wordpress.com/2022/03/pin-1-5v-ripple.jpg
>
I think that's just switching noise. You appear to be zoomed in on the
point where the main switching tran
I have been reluctant to put everything back in, in case the PSU fries
something. And the ripple I noticed is...
For the record, right now I have only the M7133, M7134 and G7273 installed.
Ok, I do recall that my 11/24 wasn't doing any ODT without some form of
memory. When I configured a (brok
> From: "Rob Jarratt"
> Thanks for the lengthy reply.
Glad to help - or try to.
> As an aside I have also been trying to find a fault on a Pro 350 which
> uses the same CPU chipset. I have a pinout but no datasheet.
There doesn't seem to be as lot on the F-11 set. I looked in th
n: 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
&
On 2022-03-28 15:49, Jonathan Chapman via cctalk wrote:
What surprises me (a little) is that there is a commercial outfit
willing to work on something so old.
It's essentially what we do. I doubt there's a directory of all the small shops
that work on legacy equipment,
but consider that some
I don't think the CPU is working at all. The reason being that there is
absolutely no LED activity. Including an LED that is supposed to indicate a
clock. Having hopefully eliminated all the power voltages it left me
wondering if there was a fault on the CPU or in the PSU. Having had activity
on t
> -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 lit
> -Original Message-
> From: cctalk On Behalf Of Chris Zach via
> cctalk
> Sent: 27 March 2022 19:48
> To: cctalk@classiccmp.org
> Subject: Re: PDP 11/24 - A Step Backwards
>
> Bigger question is who repaired the power supply "under warranty"?
A co
> What surprises me (a little) is that there is a commercial outfit
> willing to work on something so old.
It's essentially what we do. I doubt there's a directory of all the small shops
that work on legacy equipment, but consider that some of this stuff runs CNC
machines that are still in use.
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 Jarr
On 28/03/2022 04:57, Tony Duell via cctalk wrote:
Very little of the stuff I've bought new has had such seals (with some
things, like my audio equipment, you are _expected_ to remove the
covers, the user manuals tell you how. They also include the full
schematics). Ditto test gear (if there is a
On Sun, Mar 27, 2022 at 7:49 PM Bill Gunshannon via cctalk
wrote:
>
> On 3/27/22 05:17, Tony Duell via cctalk wrote:
> > On Sat, Mar 26, 2022 at 11:12 PM Rob Jarratt via cctalk
> > wrote:
> >
> >> Unfortunately, or fortunately, depending on how you look at it, the PSU
> >> repair is under warran
On 3/27/2022 11:49 AM, Bill Gunshannon via cctalk wrote:
On 3/27/22 14:48, Chris Zach via cctalk wrote:
Bigger question is who repaired the power supply "under warranty"?
My guess would be whoever fixed it this last time and warranted it.
bill
I have an Alpha DS-20 retired Feb 2021 that
> From: Rob Jarratt
> today I went back to it to check things a bit more carefully. All the
> power outputs of the PSU appear nominal.
> ...
> Presumably, whatever the part is, it is stopping the CPU working,
> because previously the CPU did appear to show some activity, al
On 3/27/22 14:48, Chris Zach via cctalk wrote:
Bigger question is who repaired the power supply "under warranty"?
My guess would be whoever fixed it this last time and warranted it.
bill
Bigger question is who repaired the power supply "under warranty"?
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 26, 2022 at 11:12 PM Rob Jarratt via cctalk
wrote:
Unfortunately, or fortunately, depending on how you look at
On 3/27/22 05:17, Tony Duell via cctalk wrote:
On Sat, Mar 26, 2022 at 11:12 PM Rob Jarratt via cctalk
wrote:
Unfortunately, or fortunately, depending on how you look at it, the PSU repair
is under warranty, which means I can't do it myself without invalidating the
warranty, so I will have t
On Sat, Mar 26, 2022 at 11:12 PM Rob Jarratt via cctalk
wrote:
> Unfortunately, or fortunately, depending on how you look at it, the PSU
> repair is under warranty, which means I can't do it myself without
> invalidating the warranty, so I will have to send it back. I don't know if
> the rippl
On Sat, Mar 26, 2022 at 9:20 PM Rob Jarratt via cctalk
wrote:
> Can anyone suggest what else the CPU might need? Or is it LTC?
>
I would check the ACLO and DCLO signals. These are both high (pulled
up by the bus terminator) for normal running, a PSU can pull them low
if it detects loss of mains
> -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 H7140
On 2022-03-26 5:20 p.m., Rob Jarratt via cctalk wrote:
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 ins
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