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Neo Geo CD PSU Help & Advice

by ResidentWeevil Sat Oct 22, 2016 6:32 pm

Hi i am a bit of a novice when it comes to electronics and i seriously hope that somebody here can help me diagnose my faulty NEO GEO CD Power Supply.

Multi-meter reads an extremely low current coming from both 5 and 10v lines, we're talking 0.8, and after opening up the unit, i found nothing wrong with any of the capacitors, resisters and what have you.

However, i did spot a bulge in one of the chips, i have no idea what it is or what it does but it's marked "MA5558". could this be the culprit?

any help on this matter would be greatly appreciated.
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Re: Neo Geo CD PSU Help & Advice

by Ziggy587 Wed Oct 26, 2016 1:42 pm

Hmm, that's a tough one. I Googled for a while and couldn't find anything.

There is an MA5558 on eBay, but it's a 4101, not a 4704 like in your pic. ... Sw5IJWfBCm

Unfortunately, the seller doesn't give a description of the item.

I found similar MA5558's on AliExpress, but it was translated from another language and I don't know how accurate it was to begin with. Some seller listed one as a voltage regulator. I found references to partial matches for multiplexers in some datasheets, but couldn't find that model number.

In your pic, you can see that it's labeled "IC102" and we know it's an 8-pin SIP package, so that's at least a start.

I don't know if that bulging is bad or not, that might just be the way it was made.

You could try probing from the power input and work your way forward to try and find an obvious bad component.

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Re: Neo Geo CD PSU Help & Advice

by ApolloBoy Tue Nov 08, 2016 12:15 am

That's actually what's called a "hybrid" IC (notice how the component is marked "IC102"). It's basically several small surface-mount components on a small board that has through-hole pins attached, and then dipped in epoxy. So that bulge you're seeing is actually the outline of a component inside the epoxy, and is not harmful whatsoever.
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Re: Neo Geo CD PSU Help & Advice

by bacteria Thu Dec 01, 2016 8:44 am

If you know what voltages go where on the board, rig up suitable regulators yourself to those points, to the correct voltages, then if the unit works you know the board is fine so it must be the transformer that is at fault. If the board doesn't work when external regulators are in place it must be an issue on the board.

I work on the principle when troubleshooting, the quote from Sherlock Homes (which was adopted by Spock in Star Trek BTW) - "Eliminate the probable, then whatever is left, no matter how improbable, must the the truth".

Many times when troubleshooting, eliminating things that are an issue using that logic, you end up with something you would not have expected, like a broken connection in a wire or something equally well unlikely. Just sayin'
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