Re: Testing Galagas

>I've been having some fun servicing a pile of Galaga boards and have found
>a few commonalities that I thought I'd share:
>
>*The custom chips legs are corroding off - spray contact cleaner on them to
>slow this down, something that leaves a fine silicon film might be best.

I shove these chips into machine pin sockets & solder the legs into the
socket. This does 2 things in my eyes. Strengthens the legs and eliminates
the silver tarnish problem.

JROK is working on replacements for some of these. I think he has a buffer
chip available for sale now 08XX?

>*White IC sockets are trash - replace them
>*Ceramic SIP resistors are trash - replace all of them!
>*Weird problems are sometimes traceable by momentarily shorting circuits to
>ground on the video board that use resistor pull-ups, the control ICs do
>not have strong pull-ups (otherwise they would not need the resistors) and
>you can learn a lot of how the images are built this way. Interesting
>watching lines appear, characters vanish, stars scroll sideways....

Is there some method to this madness?

>*The horizontal delay timing is CRITICAL and if you are getting RAM errors
>but the RAM is good, then check the 220pf cap on the delay circuit...
>
>That's all for today. But I did get in my Z80QT pod and boy that one is
>FAST on the RAM tests! A couple of seconds to verify a 1k block instead of
>a minute or two (short test). What a difference to troubleshooting time!
>

Sure rub it in! ;-)

Thanks for the tips!

Kev
Received on Sun Jun 16 07:45:27 2002