Asteroids Deluxe Repair Story Part 2

Well, after learning my lesson with cleaning the edge connector and
socketed chips' pins, I still had a problem to overcome. The game still
played blind. I knew that it needed new DAC's, so I installed a couple
AD561's (it originally used MC6012's). It was late and I didn't have any
sockets, so I just soldered them in. As you'll soon see, this was a big
mistake DOH!

Before explaining my second major mistake, I should say that I was able to
actually use my scope, logic probe, and DMM to find a bad TL082. Woohoo!
I guess I really am getting better at this stuff. Admittedly, I did call
my brother for some help, but I found the dead op amp while waiting for him
to call me back :)

As it turns out, that fixed it right up :) Well, it showed a picture at
least.. Apparently, Asteroids Deluxe doesn't really like those 561's. The
picture was shifted down and to the right quite a bit. Luckily I had my
brother on the phone at this time and he helped me figure out (well, he
told me.. I didn't help much) that the DAC had the ability to adjust the
zero'ing point by putting a 50k pot between pins 2 and 15. Here's where my
non-socketing mistake kills me.. The game board has a trace between those
pins right underneath the chip. I had to pull the chips, cut the trace,
install sockets, solder the new pots to the DAC's, and install them. Live
and learn, I suppose.

Now the game plays great, but I have a couple questions.. First, is the
hack for installing centering pots documented anywhere on the net? This
would have helped me a lot. And second, is there a reason why the black
light makes the monitor glow a little bit? It looks like the black level
needs to be adjusted, but its only the black light doing it (or maybe its
the marquee light shining through). Its so close to being perfect in
there.. I'd love to fix this.

Jon
---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Sun Jan 23 11:46:45 2000