ADM-3A Lower case ROM issue

[Ian S. King]

On Tue, Dec 13, 2016 at 5:50 PM, Steve Hatle <shatle at nfldinet.com> 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.

-- 
Ian S. King, MSIS, MSCS, Ph.D. Candidate
The Information School <http://ischool.uw.edu>
Dissertation: "Why the Conversation Mattered: Constructing a Sociotechnical
Narrative Through a Design Lens

Archivist, Voices From the Rwanda Tribunal <http://tribunalvoices.org>
Value Sensitive Design Research Lab <http://vsdesign.org>

University of Washington

There is an old Vulcan saying: "Only Nixon could go to China."