13 Sep
2006
13 Sep
'06
7:30 p.m.
I've had another look at that 9816... The error message seemed to say
that bit 12 of the video RAM was stuck low.
Anyway, I removed the text and graphics boards, the monitor PCB (which
carries the connectors these plug into) and the backplane. Then, since I
know the DIO slot pinout, I could trace data line 12 from a DIO slot to
the text PCB socket. And then on the text PCB I traced it to one side of
a '245 buffer. And from the other side to a data pin on U7 -- one of the
2K SRAM chips.
I desoldered U7 and raided my junk box for a replacement. Soldered it in
and put the machine back together.
And amazingly no more error messages.
I only got the machine today, and have no documentation at all. Hmm
-tony