2008/6/13 Tony Duell <ard at p850ug1.demon.co.uk>:
IIRC this unit is microprocessor-controlled
8085?) and the LEDs are under
the control of that microprocessor.
Absolutely correct. Everything between the processor and the LEDs in
You know, I can't rememebr the face of somebody I met yesterday, but I
rarely forget a scheamtic. Even though (in this case) I've not worked on
an LA100 for over 10 years...)
question looks to be fine so I suspect the program
just isn't running
right.
What does it use for RAM? If 2114s, then the
lucky-dip side of me says to
check/replace them. I've had _dozens_ of that chip fail in all sorts of
devices, with various odd results.
Right again, and thanks for the tip.
I think the 2114 is the most unreliable chip I've ever seen. And it
doesn't seem to be any particular manufactuer that's to blame either. I
would certainly check these very carefully.
RAM hunch. The stickers on the EPROMS' windows are
a bit crusty too,
and starting to shine through, so I'll add checking for bit rot to the
list as a last resort.
I seem to have dumps of 147E4 and 148E4 here...
-tony