1 Sep
2011
1 Sep
'11
1:55 p.m.
Well, another step forward. Thanks to Tony's advice, I continued
investigating the video output, and found another dead IC (74LS51 this
time). I'm beginning to wonder how a machine could end up with so many
faulty ICs; that's two in just the video circuitry. Maybe the original
ICs do fail, but I wonder if this board has been mistreated in some way.
PSU short to ground did something horrible. I now get
a clean video
display (which rolls on the Monitor ///, but that's not a big surprise).
At this point though, I really need to replace the crystal. Holding it
so the broken leg makes contact with one hand while powering the machine
up with the other really isn't a good way of going about things; this is
why the picture's still rolling, I can't adjust the hold on the monitor
and keep the crystal steady enough with the other hand!
Can you not solder the wire back to the crystal, at least as a temporary fix?
Silly question of the day: I'm guessing no-one would have any idea where
I'd find a 14.25045MHz crystal in New Zealand...
At one times there were companeis who would make any crystal you wanted
(within reason), the cost went up spectacularly if you wanted it very
accurate, or wanted it quickly. But if you could wait a few months for
the part, it was affordable. Radio amateurs used ot get odd crystals made
ot put ex-PMR radios on the amateur bands, for example, but I guess
that's not done much any more.
Anyhow, there may still be such compaines around,worth a look anyway.
-tony