Tech: Asteroids Deluxe

I am currently working repairing an asteroids deluxe. (anyone interested in
buying one, I have 4 at my house).
I just repaired the monitor, and I noticed that some stuff was drawing funny
on the screen.
I thought the problem was with the monitor, until I tried another AD board
in the machine.
I then put the bad PCB in another working machine and the problem came along
with it, so I know the problem is on the PCB.

Whats happening is that the Y deflection is taking too long to get to it's
starting point, but only when drawing text.
The beam is turning on and it draws a faint line up (or down) the screen
until it gets to the line of text and then it draw the rest of the line just
fine. It usually only misses about half of the first character.
So things like the first number in the score, the G in game over or the I in
insert coin are only half there with. Also when the screen come up to enter
initials, it misses half of the fisrt charater in each line of text and they
are only one line apart.
Another curious thing is that everything looks fine on a scope (this keeps
making me want to believe it's a problem in the monitor, but it does the
same thing on 3 different monitors, and only with this board)
Again, this only happens when it's moving the beam to a new location, once
it starts drawing, everything is fine.

-jeff

jeffh@diac.com

Buy/Sell/Trade classic video arcade games
http://www.diac.com/~jeffh/
Creator of new vector games
http://www.diac.com/~jeffh/vector/index.html
Received on Sat Jan 23 22:34:27 1999