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Sega Game Gear running half-speed


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Hi Folks,

I am new here. Decided to revive one old forgotten game gear. When found after lying for years in attic (exactly for 16 years).

The system was sort of running - but had corrupted display and off course hardly visible due to leaky caps. So what I did was I ordered new better screen from McWill here at the forum and installed everything... Had some issue that system was shutting down quickly after powered on. That revealed to be a problem with weak power supply which was not original and only 300mA. Of course I have "recapped" that GG completely.

And what happened..? Now GG runs, McWill display runs, sound sounds... but... all runs slow! :? :-o I mean, the game runs very slow like GG was underclocked to half CPU speed or even less....

Also music plays half-speed, I hear ding-nothing-dong-nothing etc....

Initially I thought that it could be faulty cartridge, but today I have tested it in another GG with original screen and it runs ok... Just that damned GG runs it half-speed.... :-D :?

I can't really say if that problem was present before I did screen and recap, since I only powered it up for a test and screen was corrupted...


Anybody has an idea what the hell that could be??? or head of such an issue???


also that GG shows some SEGA disclaimer on start-up for a few seconds followed by SEGA logo, while the other GG doesn't show it and shows SEGA logo only... but I guess that has to do with different version or whatever...


So any suggestions ?

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Yes, this piece of hardware was priceless few years ago, but now I have strong interest to get this thing working, even though I do not know why :)

McWill, the guy who sells improved display kit for GG, suggested to measure few capacitors and resistors responsible for CPU clocking. DOne that, all was ok and also replaced Quartz Oscillator, but problem persists...

Will try to think of what else I can do before I use different mainboard. I will keep you posted here.


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  • 2 years later...
  • 1 month later...
On 12/30/2019 at 12:21 PM, Saroulepourvous said:

Hi Airborne,


Nearly 3 years after your last post, I have the same problem you encountered. My GG seams to be very slow after installing MCWill new magnificent screen.

Can you please tell me how you solved your problem?


Many thanks for your help





I also have the same problem, did you find a solution?





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  • 1 year later...

Hello, the key question here is what is the board you are installing onto. For example 837-7996 and also where the board was manufactured e.g Japan or Taiwan. The Taiwan version has a lower crystal oscillator speed of 10.7386. Also posting pictures of your wiring will help identify any problems.

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