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  • Joined: 17 Apr 2018
  • Posts: 11
  • Location: Australia
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Game Gear power PCB repair
Post Posted: Sun Mar 28, 2021 5:42 am
I was wondering if anybody could help me repair an extremely stubborn Game Gear power supply that refuses to cooperate no matter what I throw at it. I replaced the electrolytic caps which had no effect, I then replaced the main IC and 3 power transistors which also did nothing. The guys over at RetroSix say they've yet to encounter a GG power supply that cannot be fixed by replacing those parts so I'm at a loss as to what the problem could be. I've tested it with a multimeter and it is definitely putting out the wrong voltages.

The pins on the socket normally read 5V, 5V, GND, GND, GND, 1.28V, 9V, 34V. I'm getting 3V which steadily dropped to zero on the first 2 pins, 1.27V and 8.7V for the next 2 which seems normal, and zero for the 34V pin.

So it looks like whatever the issue is it's affecting the 5V and 34V pins only. Maybe someone more familiar with this PCB than me could diagnose the problem based on this? What other parts are left that could fail? Coils? Diodes? Any advice would be greatly appreciated!
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  • Joined: 14 Aug 2000
  • Posts: 595
  • Location: Adelaide, Australia
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Game Gear power PCB repair
Post Posted: Mon Mar 29, 2021 9:16 am
Game Gears are not nice to repair.

Are you getting these measurements with the PSU connected to the GG mainboard or disconnected from the GG mainboard?

Does the pin with 8.7V stay at 8.7V throughout?

Did you test the new capacitors before you installed them on the PSU PCB?

Have you done any work or repairs to the GG mainboard?

I suggest checking the following as next steps:

Check that the capacitors been installed the right way around.

Check that the of the electrolytic capacitors pins don't measure as short circuit.

Check that the inductors for continuity and no open circuits.

Check the components you have replaced on the PSU PCB for continuity e.g. the emitter of Q3 and pin 9 of the I.C., and so on.
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  • Joined: 17 Apr 2018
  • Posts: 11
  • Location: Australia
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Post Posted: Mon Mar 29, 2021 5:27 pm
asynchronous wrote
Are you getting these measurements with the PSU connected to the GG mainboard or disconnected from the GG mainboard?

These are measurements with the PSU not connected to the mainboard.

asynchronous wrote
Does the pin with 8.7V stay at 8.7V throughout?

The pin with 8.7V stays steady at 8.7 and does vary at all.

asynchronous wrote
Did you test the new capacitors before you installed them on the PSU PCB?

I didn't test the electrolytics but they are a good quality brand (Panasonic) and I tried 2 different sets of new caps with the same result.

asynchronous wrote
Have you done any work or repairs to the GG mainboard?

Yes but I'm fairly certain this problem is confined to the PSU. I tested it on several other working GG mainboards with the same result.

Thanks for your suggestions, but I tried removing the switch and unfortunately melted it so this PSU is now toast. I think I'll try depopulating the entire PCB and replacing every part.
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  • Joined: 25 Jul 2007
  • Posts: 598
  • Location: Melbourne, Australia
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Post Posted: Tue Mar 30, 2021 9:36 am
From my own experience, you should get all the correct voltages without the power PCB connected to the main PCB, it doesn't seem to require a load to give stable voltages.

The 34v is derived from the 5v rail, so it would make sense if you aren't getting 5v you won't get 34v either.

You can have a look at the circuit diagram here
https://console5.com/techwiki/images/8/87/Game_Gear_VA1_Schematic_-_DC-DC_and_So...

and see if anything on the 5v part of the circuit might be faulty.

If it's really fried though I can highly recommend the Cleanpower PCB from RetroSix (does appear to be out of stock atm), I replace it in 3 of mine and haven't looked back.
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