Vertical Hold - Space Invaders

rob13s

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Donor 2011
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I had posted previously on general repair section, but thanks to helpful guidance I've narrow down the problem to the monitor.

I have a Midway Space Invaders upright, and the screen is scrolling right to left (viewed with the monitor rotated). I tested the power supply (it is all fine except for the 18V which appears to be dead). The game itself appears to work fine.

I took an old B&W TV that had a composite input, and connected it to pins 18 and 17 on the motherboard - and the image was there, rock solid. I have to believe that it's the monitor given this evidence.

I have the Motorola M5000. From the service manual I don't see any way to adjust the vertical hold. Also, the screen is overall about 1/2" too high (or too far to the left if the monitor wasn't rotated) and I'm not sure how I would go about fixing that either.

Don't know if it's relevant, but the monitor is makes a pretty good high pitch buzzing sound too...

Thanks.
 
Change out the caps on the chassis. That will probably take care of it...
 
The Motorola M series do not have a vertical hold adjustment (I have no idea why??). They do have a vertical size adjustment.....as far as 1/2" too high.....that's not that bad and you might have to live with it. There's two metal "rings" located at the back of the yolk. Turning these will move the image up/down/right/left, but get the sync fixed first.

Also, there's a cap on the motherboard that could be causing your sync problem. At the motherboard edge (by the power/video signal connector), there's 3 or 4 (depending on the revision of the motherboard) 10uf25V caps. At the other end of the motherboard is another 10uf25V cap all by itself. The video signal goes through this cap....change it. I've had quite a few motherboards work fine on Wells-Gardner black & white monitors, but have no sync with the Motorola M series.

Edward
 
You nailed it - the cap on the motherboard was bad as you suggested; replaced it, and the display is now rock solid. Now on to the next problem... :)
 
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