Wiring Harnesses (was: RL02 Question) - test-drb@ccmp.vtda.org

27 Mar 2018

Years ago I was troubleshooting an old SuperMicro beast that was running a
newspaper printing press. It kept shutting down randomly but if I hit the
power button it would come up. Then randomly go down again minutes or an
hour later.

I spent many hours testing and swapping modules in and out of this thing
...
 from a working machine and at one point it would only
power up if the front box that contained the power switch module and CDROM/floppy
were out of the
enclosure and separate on the bench (but still connected to the motherboard
by an data/power cables). If I got a long screwdriver and earthed this
front box to the main enclosure the machine would go down immediately.

Power switch itself tested fine with a meter but I found there was a hidden
reset swtich that wasn't in use so I desoldered and swapped them over. All
problems went away and the customer practically carried me at shoulder
height around the press hall.

-- 
adrian/witchy
Owner of Binary Dinosaurs, the UK's biggest home computer collection?
t: @binarydinosaurs    f: facebook.com/binarydinosaurs
w: www.binarydinosaurs.co.uk

---------- Forwarded message ----------
From: allison via cctalk <cctalk at classiccmp.org>
Date: 27 March 2018 at 13:32
Subject: Re: RL02 Question
To: Aaron Jackson <aaron at aaronsplace.co.uk>, "General Discussion: On-Topic
and Off-Topic Posts" <cctalk at classiccmp.org>

...
  Long short story.  I got my RL02 directly through DEC
while I was a
 engineer there.It was a pile of parts in the back lab.  The story was it was
pulled
...
  from a customersite as FS could not make it work at
install.  Seems despite being new
...
  just about everything that could be swapped apparently
was and no one could get it
...
  to spin up.   So I made a deal if I get it working its
mine (ok, to be part of
...
  the 11/23 in my office, which later would become
mine).   After assembling it and
...
  testing it sure enough it didn't spin and would
turn slowly for a few moments and quit.
...
  Drag out the meter and start testing voltages.  I
found the motor starting
 cap (known new) had odd voltages.   A bit of ohming out later it was the crimped
...
  faston connector at the end of the power line going to
the capacitor. What
...
  was wrong was crimped but the wire was never stripped
so there was no connection.
...
  The only thing never swapped was the power wiring
harness.  The pile of swapped
...
  boards and even heads was impressive.  I got the drive
and word got around
 that it was me that solved the riddle.  I troubleshot the problem, and
 didn't swap it to death. 