ADM-3A Lower case ROM issue

Jörg Hoppe j_hoppe at
Wed Dec 14 09:00:38 CST 2016

By accident, I just now restored an ADM3 (not the "A")!
Lowercase ROM was made with an pin-rearranged 2706 EPROM.
Additional RAM was inserted, DIP switches were set: works perfectly.

However, with lowercase ROM installed and DIP switches set, but extra 
RAM missing,
the Space "0x20" was displayed as a " ` ".
So I think you have an RAM issue.
Perhaps cleaning the socketed extra RAM helps?


> On Tue, Dec 13, 2016 at 5:50 PM, Steve Hatle <shatle at> wrote:
>> 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.
> Take a look at the silk screen on the board - ISTR there's another chip
> that needs to be added, some simple TTL logic.  I converted mine several
> years ago without problems - but that was with the original ROM.

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