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  • Joined: 31 Jan 2025
  • Posts: 2
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Weird contrast wheel problem on game gear
Post Posted: Fri Jan 31, 2025 12:18 am
Hello guys,
Got my hand on a game gear finally bought as non working.
In fact when powered on it just turned off immediately and without red led
The unit was recapped but the job seemed crappy, so i recapped all and started investigating the board.
it's a VA0 with 2 Asics (837-7996 European)
First thing noticed, no continuity on vref, so I bridged the chip leg directly to the power connector and it finally worked, booted up with white screen.

Then I fiddled with the contrast wheel and the screen went black and it shutdown, on subsequent power on it presented the initial problem again (but with red led)
I have been able to boot again by pushing the wheel to one end, and the screen is black
So it seems that the wheel is shorting somehow, how can i investigate the problem?also I have currently no games to test it for sound
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  • Joined: 26 Sep 2017
  • Posts: 8
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Post Posted: Mon Feb 03, 2025 12:57 pm
A good place to start would be to check the 34V voltage coming from the power board. This voltage is used to turn on the screen and therefore passes through the wheel.

Since you have already detected a problem at another voltage point, it would be wise to check all the connections on the power board to avoid short circuits.

It is worth remembering that, even if the screen is turning on, it does not mean that it is working. All voltages need to be reaching the main board, since each one performs a different function.
gear_.png (752.38 KB)
gear_.png

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  • Joined: 31 Jan 2025
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Post Posted: Tue Feb 04, 2025 12:08 pm
ashramkun wrote
A good place to start would be to check the 34V voltage coming from the power board. This voltage is used to turn on the screen and therefore passes through the wheel.

Since you have already detected a problem at another voltage point, it would be wise to check all the connections on the power board to avoid short circuits.

It is worth remembering that, even if the screen is turning on, it does not mean that it is working. All voltages need to be reaching the main board, since each one performs a different function.


All the voltages reach correctly the motherboard, since i fixed the vref i can check all the voltages and those seem ok.
I did a proper wash of the wheel with isoprophylic alcohol and now it seems that ther is no short anymore, waiting for a game to arrive to continue testing
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