K4900 Help Needed (Pic Not Centering)

Samelak

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I am putting my Multi-Williams together and I cannot get the pic to center. I am using a JROK Multi-Williams, so I am getting sync through a jamma harness. The pic below is the best I can get. Do I need horz and vert sync from the board? Any suggestions are appreciated.

 
JROK boards use negative composite sync, in spec with the JAMMA standard. so it should only use the 3rd pin of the 3 pin portion of the signal plug.

I can't tell if your picture is in a static position or if it's rolling horizontally. in my experience that's symptomatic of poor video ground, it shouldn't roll horizontally like it would if it were an H+V game and the vertical sync wasn't connected.

HOWEVER, with JROK hardware, it does have the option of CGA (standard resolution) or VGA (high resolution), which I think is set via a jumper plug. verify you're not in VGA mode!
 
It's not rolling. I was able to get it to stop in that position. I'll check the VGA/CGA jumper next.
 
i had a 4900 several years ago giving me the same issue in my dig dug game and the hold wouldn't move it like yours. i will do some checking and see if i can find what fixed it but i think it was a cracked trace somewhere.
 
I checked the CGA/VGA jumper and it was in CGA mode. I put it into VGA and got a double picture as expect. Tried anther board and got the same results with the picture not centered. More help needed.
 
I checked the CGA/VGA jumper and it was in CGA mode. I put it into VGA and got a double picture as expect. Tried anther board and got the same results with the picture not centered. More help needed.

I didn't think it was VGA, just a suggestion. to security's point, was the monitor ever worked on? did it ever work and when you plugged something in it changed? you'd be amazed at the amount of broken solder joints you find.
 
I just bought this from someone. I'll have to check with him to see if he had issues. I don't suppose this could be a cap issue?
 
most cap issues I've seen you will probably have lines at the very top and it might squish there too, and the textbook light to dark going side to side. never this.

4900 shouldn't have position pots, I think it still used headers.
 
"i finally got back to this and someone had cut the resistor out at R316 which was a 3.3K and i reinstalled and tested and it works with no more split screen.
FIXED!!!

by the way i did do a cap kit first with no change."


the above is what i found that fixed mine.
 
Fixed/Figured it out. I had the sync on the positive horizontal sync. I moved it over to the negative horizontal sync and the screen centered up. Thanks for the help everyone. Now I need someone to explain to me what happened.
 
JROK boards use negative composite sync, in spec with the JAMMA standard. so it should only use the 3rd pin of the 3 pin portion of the signal plug.

holla atcha boy! you're a champion. now play lots of Bubbles.
 
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