12 Jul
2011
12 Jul
'11
3:41 a.m.
I used the wrong term I think, inrush limiter is the right one.
Rob
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Rob Jarratt
Sent: 12 July 2011 04:10
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Identifying the Surge Suppression Resistor in PDP11 H7140 PSU
Work is continuing on repairing the H7140 PSU from my PDP11/24.
Now it seems that the surge suppression resistor across the relay has
failed.
This resistor is marked as R1 on the printset (p66 and
p69) but actually
is two
components connected in series. The parts list on p71
of the printset
lists a
3ohm 7W 5% resistor, but it is not 100% clear if this
is supposed to be
the
surge suppression resistor, although it does seem
likely.
The thing is I measured the resistance of the two resistors (in-circuit),
one was
open circuit and clearly the failed component, the
other measured 10ohms,
it
might be failing too I suppose.
The two resistors are marked KCC 13-17198-00 8234. I have not been able to
find any information on them, so I can't verify the spec and I don't know
what
to replace them with. Does anyone have any information
on these resistors?
Thanks
Rob