26 Mar
2022
26 Mar
'22
2:20 p.m.
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 reassuring
relay click.
So I powered it on. The fans turned, but there was a crackle and I smelt
something burning. I couldn't locate the smell, there were no lights on the
CPU board, but the fans continued to turn.
I had to leave it a few days and today I went back to it to check things a
bit more carefully. All the power outputs of the PSU appear nominal.
However, the ripple seems quite high, with an amplitude of 600mV on the +5V
output: https://rjarratt.files.wordpress.com/2022/03/pin-1-5v-ripple.jpg.
The DC ON light comes on, but the M7133 CPU LEDs show no activity
whatsoever.
There is no apparent damage to the CPU or to the M7134 that was also
installed. So, I guess the component that blew up must be inside the PSU.
Presumably, whatever the part is, it is stopping the CPU working, because
previously the CPU did appear to show some activity, although of course it
could still be a failure on the CPU. I am not sure what other outputs the
CPU might depend on. There is the LTC signal for the line time clock, but I
don't know if its absence would stop the CPU working. I have not been able
to test the LTC signal as yet.
Can anyone suggest what else the CPU might need? Or is it LTC?
Regards
Rob
26 Mar
26 Mar
3:06 p.m.
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 installed it and applied power to the input, I heard a reassuring
relay click.
So I powered it on. The fans turned, but there was a crackle and I smelt
something burning. I couldn't locate the smell, there were no lights on the
CPU board, but the fans continued to turn.
I had to leave it a few days and today I went back to it to check things a
bit more carefully. All the power outputs of the PSU appear nominal.
However, the ripple seems quite high, with an amplitude of 600mV on the +5V
output: https://rjarratt.files.wordpress.com/2022/03/pin-1-5v-ripple.jpg.
The DC ON light comes on, but the M7133 CPU LEDs show no activity
whatsoever.
There is no apparent damage to the CPU or to the M7134 that was also
installed. So, I guess the component that blew up must be inside the PSU.
Presumably, whatever the part is, it is stopping the CPU working, because
I think the next step would be to inspect the PSU and see if the ripple
can be eliminated, perhaps by replacing whatever blew up :)
--T
previously the CPU did appear to show some activity,
although of course it
could still be a failure on the CPU. I am not sure what other outputs the
CPU might depend on. There is the LTC signal for the line time clock, but I
don't know if its absence would stop the CPU working. I have not been able
to test the LTC signal as yet.
Can anyone suggest what else the CPU might need? Or is it LTC?
Regards
Rob
4:12 p.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Toby Thain via
cctalk
Sent: 26 March 2022 22:07
To: cctalk at classiccmp.org
Subject: Re: PDP 11/24 - A Step Backwards
On 2022-03-26 5:20 p.m., 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 ripple is caused by the blown part, but
I suppose it is likely. I may be able to inspect it without breaking the seals.
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
reassuring relay click.
So I powered it on. The fans turned, but there was a crackle and I
smelt something burning. I couldn't locate the smell, there were no
lights on the CPU board, but the fans continued to turn.
I had to leave it a few days and today I went back to it to check
things a bit more carefully. All the power outputs of the PSU appear nominal.
However, the ripple seems quite high, with an amplitude of 600mV on
the +5V
output: https://rjarratt.files.wordpress.com/2022/03/pin-1-5v-ripple.jpg.
The DC ON light comes on, but the M7133 CPU LEDs show no activity
whatsoever.
There is no apparent damage to the CPU or to the M7134 that was also
installed. So, I guess the component that blew up must be inside the PSU.
Presumably, whatever the part is, it is stopping the CPU working,
because
I think the next step would be to inspect the PSU and see if the ripple can be
eliminated, perhaps by replacing whatever blew up :)
--T
> previously the CPU did appear to show some activity, although of
> course it could still be a failure on the CPU. I am not sure what
> other outputs the CPU might depend on. There is the LTC signal for the
> line time clock, but I don't know if its absence would stop the CPU
> working. I have not been able to test the LTC signal as yet.
>
> Can anyone suggest what else the CPU might need? Or is it LTC?
>
>
>
> Regards
>
>
>
> Rob
>
27 Mar
27 Mar
2:17 a.m.
On Sat, Mar 26, 2022 at 11:12 PM Rob Jarratt via cctalk
<cctalk at classiccmp.org> 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 ripple
is caused by the blown part, but I suppose it is likely. I may be able to inspect it
without breaking the seals.
That sort of thing would make me very suspicious as to what they've
done inside the PSU that they don't want you to see.
-tony
11:38 a.m.
On 3/27/22 05:17, Tony Duell via cctalk wrote:
On Sat, Mar 26, 2022 at 11:12 PM Rob Jarratt via
cctalk
<cctalk at classiccmp.org> wrote:
Pretty much every electronic device I have ever bought had seals on
it and a notice that breaking the seals voided the warranty. Even
stuff with easily replaceable (or upgradeable) components. Nothing
unusual here.
bill
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
ripple is caused by the blown part, but I suppose it is likely. I may be able to inspect
it without breaking the seals.
That sort of thing would make me very suspicious as to what they've
done inside the PSU that they don't want you to see.
11:48 a.m.
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
<cctalk at classiccmp.org> wrote:
Pretty much every electronic device I have ever bought had seals on
it and a notice that breaking the seals voided the warranty.? Even
stuff with easily replaceable (or upgradeable) components.? Nothing
unusual here.
bill
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 ripple is caused by the blown part, but I suppose
it is likely. I may be able to inspect it without breaking the seals.
That sort of thing would make me very suspicious as to what they've
done inside the PSU that they don't want you to see.
1:12 p.m.
On 3/27/2022 11:49 AM, Bill Gunshannon via cctalk wrote:
On 3/27/22 14:48, Chris Zach via cctalk wrote:
I have an Alpha DS-20 retired Feb 2021 that was under service contract
thru 3/2021.? The PDP 11s are probably actively supported by those who
are supporting customers with active systems.? Article said use of
software and probably hardware thru the rest of the decade.
DS-20 was replaced by High Availability configuration Dell servers,
Alpha on Intel emulation.? No change to OS or software in the
migration.? Same goes for PDP 11, and possibly this was retired in such
a move with remaining warranty.? (didn't see where OP got the system.
thanks
Jim
Bigger question is who repaired the power supply
"under warranty"?
My guess would be whoever fixed it this last time and warranted it.
bill
28 Mar
28 Mar
12:53 p.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Chris Zach via
cctalk
Sent: 27 March 2022 19:48
To: cctalk at classiccmp.org
Subject: Re: PDP 11/24 - A Step Backwards
Bigger question is who repaired the power supply "under warranty"?
A company 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 26, 2022 at 11:12 PM Rob Jarratt via cctalk
>> <cctalk at classiccmp.org> 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 ripple is caused by the blown part, but I suppose
>>> it is likely. I may be able to inspect it without breaking the seals.
>>
>> That sort of thing would make me very suspicious as to what they've
>> done inside the PSU that they don't want you to see.
>>
>
> Pretty much every electronic device I have ever bought had seals on it
> and a notice that breaking the seals voided the warranty. Even stuff
> with easily replaceable (or upgradeable) components. Nothing unusual
> here.
>
> bill
>
>
27 Mar
27 Mar
8:57 p.m.
On Sun, Mar 27, 2022 at 7:49 PM Bill Gunshannon via cctalk
<cctalk at classiccmp.org> wrote:
On 3/27/22 05:17, 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 seal it voids the
calibration only), computer stuff, etc.
I don't think DEC ever put such seals on their machines when new.
Certainly not on things like power supplies,]
-tony
On Sat, Mar 26, 2022 at 11:12 PM Rob Jarratt via
cctalk
<cctalk at classiccmp.org> wrote:
Pretty much every electronic device I have ever bought had seals on
it and a notice that breaking the seals voided the warranty. Even
stuff with easily replaceable (or upgradeable) components. Nothing
unusual here. 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
ripple is caused by the blown part, but I suppose it is likely. I may be able to inspect
it without breaking the seals.
That sort of thing would make me very suspicious as to what they've
done inside the PSU that they don't want you to see.
11:50 p.m.
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 seal it voids the
calibration only), computer stuff, etc.
I don't think DEC ever put such seals on their machines when new.
Certainly not on things like power supplies,]
-tony
The RZ28 I have right here has the usual "Warranty Void If Broken" seal
on the side.
In this case the PSU was recently sent off for repair: I'm not surprised
it came back with a similar sticker.
They're not trying to stop you looking inside, they're trying not to
have to fix it again for free after you've fiddled.
What surprises me (a little) is that there is a commercial outfit
willing to work on something so old.
Antonio
--
Antonio Carlini
antonio at acarlini.com
28 Mar
28 Mar
12:49 p.m.
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. Depending on the industry and product, it's *way* cheaper to keep an
old machine that's run not-full-time operational than to retool and recertify.
Thanks,
Jonathan
1:01 p.m.
On 2022-03-28 15:49, Jonathan Chapman via cctalk wrote:
including Nuclear power stations!
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. Depending
on the industry and product, it's *way* cheaper to keep an old machine
that's run not-full-time operational than to retool and recertify.
Thanks,
Jonathan
12:55 p.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Antonio Carlini
via cctalk
Sent: 28 March 2022 07:50
To: cctalk at classiccmp.org
Subject: Re: PDP 11/24 - A Step Backwards
On 28/03/2022 04:57, Tony Duell via cctalk wrote:
Me too, but they do!
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 seal it voids the
calibration only), computer stuff, etc.
I don't think DEC ever put such seals on their machines when new.
Certainly not on things like power supplies,]
-tony
The RZ28 I have right here has the usual "Warranty Void If Broken" seal on
the side.
In this case the PSU was recently sent off for repair: I'm not surprised it came
back with a similar sticker.
They're not trying to stop you looking inside, they're trying not to have to fix
it again for free after you've fiddled.
What surprises me (a little) is that there is a commercial outfit willing to work
on something so old.
Antonio
--
Antonio Carlini
antonio at acarlini.com
27 Mar
27 Mar
2:14 a.m.
On Sat, Mar 26, 2022 at 9:20 PM Rob Jarratt via cctalk
<cctalk at classiccmp.org> 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 or whatever. Normally that will halt the
CPU
-tony
30 Mar
30 Mar
2:29 p.m.
I found these two signals and ACLO is low (-15V) so I guess this must be the problem and
whatever blew inside the PSU is probably the reason this signal is low. DCLO is high and
the DC ON light is illuminated, but the CPU doesn't do anything presumably because
ACLO is asserted.
Regards
Rob
-----Original Message-----
From: Tony Duell <ard.p850ug1 at gmail.com>
Sent: 27 March 2022 10:15
To: rob at jarratt.me.uk; Rob Jarratt <robert.jarratt at ntlworld.com>; General
Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: PDP 11/24 - A Step Backwards
On Sat, Mar 26, 2022 at 9:20 PM Rob Jarratt via cctalk <cctalk at classiccmp.org>
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 or whatever. Normally that will halt the CPU
-tony
998
days inactive
1002
days old
15 comments
9 participants
participants (9)
-
a.carlini＠ntlworld.com -
ard.p850ug1＠gmail.com -
bill.gunshannon＠hotmail.com -
cz＠alembic.crystel.com -
g4ajq1＠gmail.com -
jwsmail＠jwsss.com -
lists＠glitchwrks.com -
robert.jarratt＠ntlworld.com -
toby＠telegraphics.com.au