Asteroids Monitor problem

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I have an Asteroids game that when powered up, works great, except for
one small problem... The display is shrunken in the bottom 1/3 of the
screen. It used to work great, but now it seems like someone
miniaturized it. No one has touched the monitor, but I haven't tried
any adjustments yet either. I wanted to see if someone could help
diagnose it before I went searching.

Thanks
Rodney

 

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Archived from groups: rec.games.video.arcade.collecting (More info?)

> have an Asteroids game that when powered up, >works great, except for
>one small problem... The display is shrunken in the >bottom 1/3 of the

There are x-y pots on the CPU, but I don't know if that is going to fix
your problem. You could have bad deflecting transistors, or the output
of the board is bad. Is it a FULL screen on the lower 1/3 or is it a
chopped off version?

 

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It is a FULL screen, just really tiny asteroids and ship. It still
functions.

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

>It is a FULL screen

You can try the x-y pots on the CPU. you may have to do some monitor
work if you can't get them full screen. You can also center the screen
by messing with the yoke.

Kirb

 

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Archived from groups: rec.games.video.arcade.collecting (More info?)

I have a guess at it, some of the big dogs may say I'm wrong....

I remember when I fixed my Asteroids Monitor (Thanks to Kirb for the
great warehouse raid), I found that the 4 bottle cap transistors on the
chassis controlled the top and bottom Y and the left and right X. It
may be possible that the bottom Y transistor is not getting enough
power, is slightly grounded (dried out protector), or is just going
bad. This would mean that the magnetic field wasn't getting biased
enough, therefore the shrinking image would be because the beam isn't
being pulled down enough.

Anyone think this is a valid theory?