ADM-3A Lower case ROM issue
shatle at nfldinet.com
Tue Dec 13 19:50:38 CST 2016
I acquired an ADM3-A a while back from the NWA auction, and a
generous friend was able to get me the lower case ROM chip that
was "missing" from my terminal.
I set the DIP switches and installed the ROM. When I turned on the
terminal, the whole screen was filled with "`" characters before the
host was ever started.
When I started up the connected Sun machine, the terminal did display
both upper and lower case characters, but the "`" characters remained
and appeared to fill out each new line, and text printed out by the
machine was followed by garbage characters - like "Login:nzzzz". Typed
characters were correctly upper or lower as typed.
I removed the ROM and cleaned the legs of the chip. I didn't clean the
socket, since I didn't have anything like DeOxit handy. I did remove and
re-insert the ROM a couple of times.
When I removed the ROM and set the DIPs back to the original setting,
the terminal worked like normal in all upper case. Setting the DIPs to
force upper case, etc. when the ROM was in always showed the bad
behavior though the characters were upper/lower as you would expect from
the switch settings.
TL;DR - bad and extra characters when the ROM chip is in, everything OK
when it's out.
So, barring a bad connection to the chip while it's in the socket, it
seems like the ROM itself could be bad. I'll dig through the maint
manuals and see if I can find anything related to this behavior. In the
meantime, any ideas from the collective are welcome.
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