[sebhc] ET-3400A Repaired

[peter b. nelson]

Paul,
    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.

Yours Truly
Peter Nelson

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 
> chips
> that came with the ET-3400A are too fast or too slow, but they don't 
> work.
> A quick search on Google showed 250 nS for the bad boys and 450 nS for 
> the
> ones that worked.
>
>    Also, I cleaned the sockets with Caig "DeoxIT" and a toothpick, and 
> then
> 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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