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Tryout and teardown of two Tandy Colour Computer 2s

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intabits:
To help with repairing my Compacta Uniboard, I was looking for a working 6809 based system to help develop a ROM emulator gizmo using a RAM chip.

I have an old Tandy Colour Computer 2, that I tried to fire up after 35 years of storage:-




No joy there, so I bought another CoCo to satisfy my original aim, and also to help with fixing the first CoCo:-



At least that one works.

Now to play with RAMs, ROMs and CoCos...

W0MJ:
Posting a picture is hanging-up my post;  so i will 'just post' then try the picture.
I have seen the "?_" prompt, but only occassionally, and only if i have DIP switch 2 set to 'off' (monitor and keyboard versus serial I/O).
i cleaned the pins of all chips except the RAM 932 of them!) and it came up, reset a few times, and looked good;  i do not have a keyboard wired correctly, so i could go no further.  I tried to chagne the DIP switch to serial I/O, and got the RAM dump screen.  dang.

I will try to post a picture....

Thanks!

-Matt

W0MJ:
Uniboard pictures

W0MJ:
... that should be (32 of them), i.e. the count of RAM chips;  the shift did not shift and i ended up this a lot more memory! <grin>

The keyboard i have is from a broken (non-repairable) piece of test equipment, a Nicolet analyzer - it had literally fallen off a truck, but the keyboard is intact.  The encoder chip is an OKI part, MSM3914-34RS - any info on that one?  i can kinda guess as to the data and strobe lines, and maybe the power;  but i would hate to be wrong.

Any help appreciated. I found an OKI data book but it only has processors.

Once i get the keyboard 'correct', i can try to go further, if and when i get the prompt again (like memory test).

ozcar:
Reading this prompted me to dig out an eprom programmer I made "only" around thirty years ago, using a 6809. The challenge was finding the somewhat strange serial cable I used for the thing, but I found it still works!

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