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Author Topic: G07-C0B Monitor sync issues. Screen is shifted 1/3 to the left.  (Read 308 times)

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elderjag

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Okay, first off, I'm a newbie.  I tried searching the forum but got an error in the search.  So if there is a post about this, please forgive me for the post. 

I recently was given an old Zaxxon cabinet.  It had a monitor and some transformers and a jamma harness installed.  the monitor wires were just hanging in the back of the cabinet.  I bought an atari Tetris jamma board, so I could build a tetris game for my wife(her favorite game).  I checked all of the jamma wires and double checked them.  i connected the monitor to the jamma harness.  Turned on the game and the game loaded, but the screen was shifted to the left by 1/3 to 1/4 of the picture.  I tried to adjust the H freq and could get the picture to shift right just a little but then it would scramble up.  The screen would also scroll upward a little.

I tried to get that to stop by adjusting the v hold but it would scroll up and stop for a few seconds then scroll again. 

so everything i have found points to the h sync and v sync.  i found a manual for the tetris board and also for the G07. 
Im just unsure of how these sync wires hook up.  there is only one sync wire on the jamma harness, but the board has an optional 11 pin video out spot for a harness. do both the positive and neg syncs need to be connected?

 

grantspain

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Re: G07-C0B Monitor sync issues. Screen is shifted 1/3 to the left.
« Reply #1 on: August 13, 2020, 06:43:47 am »
no, you may need to link negative v sync and h sync

there is also a mod for running later games boards, you can find it by browser search

Ken Layton

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Re: G07-C0B Monitor sync issues. Screen is shifted 1/3 to the left.
« Reply #2 on: August 13, 2020, 11:06:25 am »
http://homearcade.org/BBBB/sync.html

Just scroll down to the Electrohome G07 section.

elderjag

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Re: G07-C0B Monitor sync issues. Screen is shifted 1/3 to the left.
« Reply #3 on: August 18, 2020, 03:14:42 pm »
okay so after many many hours of beating my head on the cabinet, I finally got the screen to work correctly.  the monitor has a 3 pin and 6 pin connector.  I hooked up the 4 wires on the 6 pin connector and moved the other 2 for the sync to the 3 pin connector.  The screen id finally centered.

form what i have read, the 6 pin connector on the chassis is sync positive and the 3 pin connector is sync neg.  The tetris board sends a sync neg signal through the jamma.  The tetris board also had a video signal 11 pin harness besides the jamma cable signal.

Thanks for all the help