8 Jun
2020
8 Jun
'20
10:30 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
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