GameGear - The case of the missing brightness dial

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beebogates
Posts: 7
Joined: Mon Sep 03, 2012 11:30 am
Location: Cairo, Egypt

GameGear - The case of the missing brightness dial

Post by beebogates » Mon Sep 03, 2012 11:47 am

Hi everyone,
So I spent this weekend going through various flea markets looking for a working game gear. I was only partially lucky, found one almost complete unit and some spare parts.
I figured the problem with the most complete unit would be the leaky capacitors, as always. So I set out to replace them. In the process, I made this awful discovery: none of the units I picked up had a brightness dial. None. All I found were the solder points where the brightness dial would be.

So I finished replacing the capacitors, and shorted out the pins to the brightness potentiometer, and then turned the unit on. It worked! both sound AND screen were very acceptable.
However, only a minute later, I started hearing this hissing sound, the unit started acting up, smelled like burning, then the light went out.

I think I may have burned the CFL tube by shorting out the brightness potentiometer. Or maybe the CFL tube had a crack and was nearing its life expectancy. Or maybe something else burned.. I can't tell what it is right now, so I need your help. Right now, the unit power LED lights up, sound works perfect, but the screen doesn't light up.

Any ideas? I know that if it turns out the fluorescent lamp is dead, I can just go ahead and replace it with LED's. However the problem with that is, LED's still require a brightness dial. So I believe step 1 would be fixing the brightness dial. Sadly, I couldn't locate any spare potentiometers, so I'll be more than happy with a "fixed" brightness setting using a fixed resistor. I just don't know what value to use or how to connect it.

Thanks all.

beebogates
Posts: 7
Joined: Mon Sep 03, 2012 11:30 am
Location: Cairo, Egypt

Re: GameGear - The case of the missing brightness dial

Post by beebogates » Tue Sep 04, 2012 2:16 pm

Update - there haven't been any changes, I re-checked all capacitors, everything solidly soldered and in good order.
I should mention that the only replacement capacitors I found were of MUCH higher voltage ratings than the original. So in place of 6.7 volts, the least I found were rated for 16 volts.. but had the correct capacitance. I was told that voltage doesn't matter as long as it's the same as or greater than the original, but just thought I'd mention it.

With a basic multi-meter I powered the unit on and checked if there was an AC current accross the CFL tube. Nothing - zero voltage. I then checked both fuses on the sides of the screen, and they weren't broken.

Please help - I am rather desperate. I live in Egypt, which means I can't get a game gear off ebay, there are no retro game stores here, and I've had to do some serious dumpster diving to find what scarce number of parts that I have now.. and I'm very keen to bring them back to life.

beebogates
Posts: 7
Joined: Mon Sep 03, 2012 11:30 am
Location: Cairo, Egypt

Re: GameGear - The case of the missing brightness dial

Post by beebogates » Tue Sep 04, 2012 6:06 pm

Another clue - just went in with my multimeter again. There's no current across capacitors C37 and C39 - the big ones right next to the screen.
I checked all other capacitors, all good. Solder pads conducting nicely, no visible trace breaks, and no visibly damaged or burned components on visual inspection.
Seems like this section of the mainboard isn't getting any power for some reason. I'm running out of ideas.

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