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I have a GameGear that had lines through the screen. I replaced the main board caps and the game powered up and I was able to play. I powered it on and off twice and then it died.

The main board appears fine. The power board is acting strange.

My AC Adapter says 10v .85a, but my mutli meter reads 13v coming out. On the power rails all read the AC adapter (or battery) voltage. No stepping down is occurring. I replaced the caps on the power board and it's the same issue currently.

Did the power board fry my game gear by sending 13v down the two 5v rails?

I do not have a working power board to test the main board currently.

Anyone have any ideas here while I'm trying to trace the circuitry out to figure out why this is happening?

tldr;
power board isn't stepping down or up on voltage(even after cap change)
grounds are fine on three pins
two 5v rails and 36v all show the same as the power source voltage

Theres a service maual here. It might be for a different model to yours but the power supply should be the same, or very close.

http://www.smspower.org/forums/14053-MasterSystemGameGearServiceManuals?start=100#74018

Its a switching supply and sounds like its not switching. The controling ic monitors the output voltages so should shut down if the output voltages run out of spec, which its not doing. I would start by checking Q3 and make sure its not shorted.

As for the condition of the main board.. if its had 13v on the 5v supply rails it may not be happy. You would have to fix the supply issue first and see what happens from there i guess. I suggest not plugging the power supply into it again untill its sorted to prevent any further damage tho.

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Milenko2121 Joined: 02 Jan 2018 Posts: 1	Repairing a Game Gear, power board issue question. Posted: Tue Jan 02, 2018 8:28 pm
Milenko2121 Joined: 02 Jan 2018 Posts: 1	I have a GameGear that had lines through the screen. I replaced the main board caps and the game powered up and I was able to play. I powered it on and off twice and then it died. The main board appears fine. The power board is acting strange. My AC Adapter says 10v .85a, but my mutli meter reads 13v coming out. On the power rails all read the AC adapter (or battery) voltage. No stepping down is occurring. I replaced the caps on the power board and it's the same issue currently. Did the power board fry my game gear by sending 13v down the two 5v rails? I do not have a working power board to test the main board currently. Anyone have any ideas here while I'm trying to trace the circuitry out to figure out why this is happening? tldr; power board isn't stepping down or up on voltage(even after cap change) grounds are fine on three pins two 5v rails and 36v all show the same as the power source voltage

wasup Joined: 05 Nov 2014 Posts: 435 Location: Auckland - NZ	Posted: Wed Jan 03, 2018 3:28 am
	Theres a service maual here. It might be for a different model to yours but the power supply should be the same, or very close. http://www.smspower.org/forums/14053-MasterSystemGameGearServiceManuals?start=100#74018 Its a switching supply and sounds like its not switching. The controling ic monitors the output voltages so should shut down if the output voltages run out of spec, which its not doing. I would start by checking Q3 and make sure its not shorted. As for the condition of the main board.. if its had 13v on the 5v supply rails it may not be happy. You would have to fix the supply issue first and see what happens from there i guess. I suggest not plugging the power supply into it again untill its sorted to prevent any further damage tho.

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