The data lines are used for some other function
(contrast control I
think), so if that works the 6522 is probably working. If there's a hard
disk problem it's in the Widget itself.
Now that's interesting. The knob which I assume is the contrast (just below
the brighness one) appears to do absolutelyt nothing?
I don;t think it relates to a physical knob... There is a DAC on the I.O
board (see sheet 5 of the schemaitc I think) that is fed from the same
VIA port as the data lines to the Widget (the latter are buffered by a
'245 chip) -- I think the CIA and buffer are on sheet 2. I've not traced
the output of the DAC in detail, and some bits of schematic don't seem to
exist on the site I was looking at, like the backplane, but I thoguht the
schemaitc implied that DAC was some kind of software-controlled contrast
facility.
-tony