8 Jun
2020
8 Jun
'20
7:10 a.m.
Hello
I have a couple of VAXstation 3100s - a M38 which boots but has no output
on the console port, and another model which has corrosion on the
motherboard and a PSU which doesn't power up correctly.
The voltage on all of the M38 PSU's pins is OK except for pin 7 (brown)
which is +3.5v to +5.25v DC and is floating at about 0.6v with reference to
ground. I suspect this is why the console port doesn't work (and the LEDs
on the read suggest a RAM problem so I can't tell which chip is faulty), so
I've set about troubleshooting.
Does anyone have any suggestions above and beyond replacing capacitors?
Peter
--
OpenTrainTimes Ltd. registered in?England and Wales, company no.?
09504022.
Registered office: 13a?Davenant Road, Upper Holloway,?London N19
3NW
8 Jun
8 Jun
7:30 a.m.
Peter,
This is just generic advice based on recent experience. I would replace all electrolytic
caps. I had some test pretty good, but PSU worked after I replaced them. Also check all
the rectifier diodes as well, and I have had an opto-isolator fail.
Dave
-----Original Message-----
From: cctech <cctech-bounces at classiccmp.org> On Behalf Of Peter Hicks via
cctech
Sent: 08 June 2020 15:10
To: cctech at classiccmp.org
Subject: VAXstation 3100 power supply
Hello
I have a couple of VAXstation 3100s - a M38 which boots but has no output
on the console port, and another model which has corrosion on the
motherboard and a PSU which doesn't power up correctly.
The voltage on all of the M38 PSU's pins is OK except for pin 7 (brown) which
is +3.5v to +5.25v DC and is floating at about 0.6v with reference to ground. I
suspect this is why the console port doesn't work (and the LEDs on the read
suggest a RAM problem so I can't tell which chip is faulty), so I've set about
troubleshooting.
Does anyone have any suggestions above and beyond replacing capacitors?
Peter
--
OpenTrainTimes Ltd. registered in England and Wales, company no.
09504022.
Registered office: 13a Davenant Road, Upper Holloway, London N19
3NW
7:32 a.m.
Hi Dave
Superb, thanks - I hadn't thought about the rectifier diodes.
A word of caution for anyone replacing the 470uF/250V electrolytics near
the mains side of the board: the Nichicon like-for-like replacements are
shorter and wider than the ones they replace and don't actually fit.
Peter
On Mon, 8 Jun 2020 at 15:30, Dave Wade <dave.g4ugm at gmail.com> wrote:
Peter,
This is just generic advice based on recent experience. I would replace
all electrolytic caps. I had some test pretty good, but PSU worked after I
replaced them. Also check all the rectifier diodes as well, and I have had
an opto-isolator fail.
Dave
--
OpenTrainTimes Ltd. registered in?England and Wales, company no.?
09504022.
Registered office: 13a?Davenant Road, Upper Holloway,?London N19
3NW
-----Original Message-----
From: cctech <cctech-bounces at classiccmp.org> On Behalf Of Peter Hicks
via
cctech
Sent: 08 June 2020 15:10
To: cctech at classiccmp.org
Subject: VAXstation 3100 power supply
Hello
I have a couple of VAXstation 3100s - a M38 which boots but has no output
on the console port, and another model which has corrosion on the
motherboard and a PSU which doesn't power up correctly.
The voltage on all of the M38 PSU's pins is OK except for pin 7 (brown)
which
is +3.5v to +5.25v DC and is floating at about
0.6v with reference to
ground. I
suspect this is why the console port doesn't
work (and the LEDs on the
read
suggest a RAM problem so I can't tell which
chip is faulty), so I've set
about
troubleshooting.
Does anyone have any suggestions above and beyond replacing capacitors?
Peter
--
OpenTrainTimes Ltd. registered in England and Wales, company no.
09504022.
Registered office: 13a Davenant Road, Upper Holloway, London N19
3NW
1658
days inactive
1658
days old
2 comments
2 participants
participants (2)
-
dave.g4ugm＠gmail.com -
peter.hicks＠poggs.co.uk