14 Jul
2011
14 Jul
'11
9:38 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Tony Duell
Sent: 12 July 2011 21:37
To: cctalk at classiccmp.org
Subject: Re: Identifying the Surge Suppression Resistor in PDP11 H7140 PSU
I have been looking at the same printset as Tony has.
Dave, is there any chance you could photograph the fiche pages for the input
assembly and the bias and interface board? Regardless of image quality it
would still be better than nothing.
there are two designs of the relay assembly on the H7140 fiche here,
the old ones parts list has a Resistor (R1) 3 ohm 5% 7 W 13-14848-00
That's the one shown in the printset on Bitsavers (and in my paper 11/44
printset)
the new one has a sub assembly on that with thermistor listed as
Thermistor 7.0 10% dec part number 13-17198-00
Looks like my guess 'it's a DEC part number' was right.
Waht does the 7.0 refer to here? The cold resistance? If so, it sould be
possible to find soemthign that will work. The physical dimensions of the
original part will give some idea as to the current rating.
Are there any other changs between the 2 versions of the PSU? If you
fitted a
3 Ohm reistor to the later version, would it work
correctly?
What was the reason for the change?
One question I have is this. My bias and interface board had what looked
like a broken track, and it did look broken rather than deliberately cut.
However, could you look at the fiche printset you have, which probably
corresponds more closely to the PSU I actually have, and tell me if the
collector of Q2 (p87 of the other printset on bitsavers) is connected to
anything?
Dave Caroline
-tony