On 5/27/2013 2:33 AM, Dave wrote:
  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. 
Right, they're not logic chips, I misspoke :).
 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).....
 
 
They're fully encapsulated in plastic / resin.  For some of these it may
be possible to solder to a new carrier, but some are pretty far gone and
it might be more of a challenge to get a good connection.
I've put up a picture at:
https://plus.google.com/u/0/photos/117997069161125071032/albums/58769649993…
And yeah, $5/each is not going to be cheap.  And I also need to replace
a number of multi-transistor packages (Q2T3725's) which seem to go from
$7-$10 (if I can even find them).  I'm definitely going to try the
repair route first, but it would be good to have a source for
replacements just in case.
Thanks,
- Josh