21 Feb
2009
21 Feb
'09
5:41 p.m.
At 05:04 PM 2/21/2009, arcarlini at iee.org wrote:
cctalk-bounces at classiccmp.org wrote:
If the cables between your power supply and the backplane are ribbon
cables with IDC connectors, they can overheat (often you'll find them
showing discoloration.) If they're separate wires with white connector
blocks, you have the updated harnesses.
I haven't seen this problem with BA23 boxes, but have seen several
BA123 boxes with signs of overheating.
-Rick
IMHO the most important thing to do after
checking for
obvious problems
-- loose parts, evidence of overheating/burning, etc, is to test the
power supply (PSU) on a dummy load. A defective PSU could
wipe out every
chip in the machine!.
In addition, pay particular attention to the PSU wiring harness.
The early rev of harness on (iirc) the BA23 had a habit of
catching light. I think it was slightly underrated for the
maximum power load and so would deteriorate over time. It
would eventually reach the point where one of the N conductors
would fail, leaving N-1 carrying way too much load and smoke
ensued.
Field service were (again, iirc) supposed to swap these out if
they came across them. But if your machine has truly not been used
for twenty years, it ended up in storage relatively eraly in its
life and so may not have had a chance for some FS TLC.
A little bit of googling should find you the relevant details
(or you could wait for the next post which will no doubt be
from someone with much better memory than me :-)).