16 Dec
2009
16 Dec
'09
3:21 p.m.
Thanks to everyone's advice. You were all right (as was my original
suspicion)...that it was the video memory.
Thanks to the pointers on where the video memory was (I don't have
schematics or other tech info on this system).
I was able to find the bad memory...and, amazingly, I found that I had
another 2114 that I could put in (I took it out of my heathkit
microprocessor-trainer. And it makes the trs-80 work much betta!
Well done!/ Repairing this old hardware can be fun, and it's a great
feeling when it works again (or at least is is for me).
So...a couple of questions:
1) How can I get just 1 2114 that works to replace the one I took
out of my heathkit? (the place that people pointed-out for buying chips
has a $25 minimum..and I don't need that many chips).
Get more 2114s :-). In my experience it's one of the most unreliable
chips there is, to the extend that I've replaced them in just about
everything I've got that uses 2114s at some time or another. For example,
I ought an HP9836CU (a complex 68000-based computer) and it had curious
floppy controller problems. Soetimes the floppy controller wasn't even
found by the self-tests. As soon as I saw the floppy controller board had
a pair of 2114s on it as a data buffer, I changed them. And the problems
went away.
Is there any other electronics or classic computer enthusiast near you
who would be prepared to add a couple of 2114s to his next order? that
would get over the minimum order charge.
2) What can I do with a model II now? When it is
booted into CP/M,
will it only run CPM stuff specifically for the trs-80 or will it run
any CP/M stuff that is on 8" floppy?=20
AFAIK, unlike some M1 and M3 CP/Ms (which needed specially relocated
progrtams), the M2 CP/M will run any standard CP/M programs.
-tony