On 2013 May 26, at 4:38 PM, Josh Dersch wrote:
I've started looking at what it's going to
take to get the memory
in the Imlac running again. There are two core assemblies in this
machineand they're both in pretty bad shape as they were exposed to
moisture for a long enough period that they accumulated quite a
bitof corrosion on the control logic. (The cores themselves seem
to be OK).
I went over the better of the two assembliesand cleaned the legs of
every socketed IC. In the course of doing so I found maybe 10
chips with legs that were falling off. I took alook at a random
sampling of chips from the worse of the two assemblies and every
single one of them has legs that are corroded through. So I'm
going to be replacing a lot of chipsif I want to get these running
again.
Most of these are 7400-series logicand aren't hard to find.
However, there a set of components that I'm not too familiar
withand I'm not having much luck finding replacements. Now that I
have the schematic I at least know what they are(had no luck
looking them up based on the labels on the chips), they're
described as "Transformer, 60uH", "Transformer, 6uH" and
"Transformer, Square Loop" and have part numbers of 517A0024,
517A0023, and 517A0021.
The chips themselves that are in my machine are labeled as follows
(for the 60uH variant):
14201
NPIPA-2581
<date code>
These are in 16-pin DIP packages. I'm going to need to replace
quite a few of them.
Any ideas of a modern replacement? (Any idea where to source NOS or
used ones?) I can provide pictures if that'll help.
I have a large scrap core memory driver/interface board with a
quantity of 8 and 16 pin pulse transformers on it (dual and quad packs):
2624-7486
NPI
NP-5163
7912H
and
2624-7429
NPI
NP-3142
7846H
The 2624- numbers appear to be Burroughs house numbers as I think the
board is from a Burroughs machine, the 79xx/78xx date codes.
I wonder if NPI was the transformer manufacturer. I RE'd the board so
I do have a schematic that shows how they are used but don't know
anything about their specs beyond that.
As I suggest in another message, another possibility might be to
investigate ethernet-isolation transformers.