[sebhc] ET-3400A Repaired
peter b. nelson
peter at peternelson.com
Tue Feb 27 08:24:26 CST 2007
Thanks for the updates. I subscribed to this list after buying an
old ET3400A, and it's been nice to read some relevant postings lately.
My own recent "repair" issue was this: after not using the ET3400A
for several months, I went to demo it to my brother-in-law, and
naturally it didn't work. It seemed to be resetting itself 100
times/second -- all it showed was a flickering "CPU UP". Slapping it
down, hard, on the table seemed to stabilize it enough to demo, but it
still did an auto-reset every ten minutes, erasing my program and
displaying "CPU UP".
Fortunately, removing and re-seating all the chips solved the
problem. It's currently at about two weeks uptime, with no issues.
Paul A. Pennington wrote:
> I thought I would let everyone know what I finally found was wrong
> with my
> ET-3400A, in case anyone else runs into it. There were contact
> problems from oxidation on the chips and sockets as some have
> suggested, but the main problem was the two 2114 memory chips. I
> finally tried two different chips and everything started working.
> I had tested the memory early on by plugging it into my ET-3400, where
> it worked. But, the clock is much slower there. I don't know if the
> that came with the ET-3400A are too fast or too slow, but they don't
> A quick search on Google showed 250 nS for the bad boys and 450 nS for
> ones that worked.
> Also, I cleaned the sockets with Caig "DeoxIT" and a toothpick, and
> sprayed them with "ProGold". I also scraped the inside of the chip legs
> with a small screwdriver.
> Anyway, everything works reliably now. That was a tough one. At
> least, I dusted off my test equipment and got my IC tester and EPROM
> reader/programmer working again.
> Paul Pennington
> Augusta, Georgia
> Delivered by the SEBHC Mailing List
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