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Mysterious PSU Chip - please help!

Discussion in 'Power Electronics' started by Andy217, Oct 23, 2016.

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  1. Andy217


    Oct 23, 2016
    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 console Power Supply.

    The power cord to the games console has three pins, two voltage lines (5V and a 10V) as well as Send. My 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?

    If so, could somebody please tell me what kind of chip it is and where i can get a replacement/alternative or upgrade? i would sincerely be in your debt.

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  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Don't worry about those lumps. That device has lumpy things under a coating.

    How did you measure the current? Please tell me you didn't place a multimeter on the current range across the output.

    Why do you suspect the power supply of having failed?

    What voltages does it give you on the outputs?
  3. davenn

    davenn Moderator

    Sep 5, 2009
    That is a hybrid circuit with a mix of any sort of components on a ceramic wafer

    have you actually googled that number ?

    There is at least one source of the part

  4. Andy217


    Oct 23, 2016
    Yeah First thing i did and couldn't find much information on it. i did find a couple for sale on aliexpress but i really don't trust that site at all.

    If by that, you mean putting the black probe on ground and then testing the 5 and then 10V with the positive probe then yes. it read something like 0.8 on both.
    Now being a complete novice and not trusting my ability to use a multimeter, i then tested the them again using an L.E.D. the bulb was extremely dim and would pulse - no difference in brightness from both outputs.

    Thank you both for replying, i appreciate this. :)
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    So did you have the multimeter set to a voltage or current range?

    And what prompted you to "test" this power supply.

    As far as I can tell right now, what you are seeing could be as a result of the power supply protecting itself.

    Measure the output on a voltage range and tell us what you get.
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