On 27/05/2013 00:38, 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.
Thanks,
Josh
These are almost certainly pulse transformers, not "chips" as such,
so
real miniature transformers. Try a google search on "core memory pulse
transformer" here are two I found usefull.
http://www.dtic.mil/dtic/tr/fulltext/u2/045016.pdf
https://sites.google.com/site/wayneholder/one-bit-ferrite-core-memory
Given that I wonder if its possible to salvage the original "innards"
and mount them on a 16-pin dip carrier. Have you tried opening one up or
are they fully encapsulated in a solid material. If they are solid is
there enough material left to solder to a 16-pin carrier. I think photos
would help. Finding modern replacements sounds fun and expensive (about
$5 min).....
Dave
G4UGM