Exidy Death Race video sync

thebman80

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I just get an Exidy Death Race PCB and I'm having trouble getting the picture to SYNC right. I can sometimes get a stable picture but there is always something wrong with it. I have tried using composite video to a TV and I have tried going through my monitor on my test bench.

Composite video on a small black and white TV I get this

20161231_151819.jpg


On my test bench I get this

20161231_163430.jpg


20161231_164016.jpg


Now I read that trying to isolate the SYNC out of the video circuit can help and I found this in the original schematics. Problem is that the place where the SYNC is labeled in the schematics says it comes out of pin 10 of chip 15 A and that leg goes to a resistor R130 when I checked that pin just goes to nothing and none of the resistors or other parts on the PCB are silk screened with numbers. Only the primary chip locations seem to have any number and lettering system.

Schematic

death%20race%20video%20sync.png


Here is a picture of pin 10 chip 15A top and bottom nothing just a floating leg.

pin%2010%20top.jpg


20170102_125352.jpg


Any ideas as to how I can get this picture to SYNC up right? Also anyone have a schematic that has all the parts on the PCB labeled? It would save me the trouble of actually making one myself which I might.
 
Ran into the same problem a few months ago, while fixing a game board for a friend

Death Race used a XM702-10 monitor.....runs at 17.3Khz (not the standard 15.75). I could not get it to sync with any of my "modern" monitors

Mike
 
I just figured it out, apparently the schematics above are correct. But the trace runs under the chip to the resistor as soon as I multimetered it I confirmed it. So I jumped the SYNC off the chip side of the resistor and the video stabilized like a rock. Problem now is that the car sprite is still not SYNCing and when the Gremlins walk into the same plane as the car they to go out of SYNC. As soon as the gremlins walk out of the cars plane they go back to normal.

So jump the wire off of the IC side of the 5.1k resistor which is R130. Or just jump it right off pin 10 of IC A15 which will work the same.

20170102_162947.jpg


Here is the picture now with the out of SYNC car. Could I be missing some sort of SYNC signal for the car?....

20170102_163002.jpg
 
Ok so I just went back to take a look again and this happened

20170102_170315.jpg


As the gremlins walked around they would go in and out of SYNC randomly. After a few more times turning it off and on different sprites would randomly go in and out of SYNC. So it looks like its some sort of TTL problem that controls all of the sprites.
 
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