1. dicamarques

    OP dicamarques Definitely not Bruce Wayne.
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    Just got a switch handed over to me that doesn't turn on, check it with a multimeter and the battery does indeed charge.

    Tested the caps around the MT chip and found no shorts.
    The only shorts I found were the big caps around one of the buck regulators MAX77621AEWI+T
    upload_2021-1-24_10-54-39.png .
    .

    After that, I tested some voltages on the back of the board:

    upload_2021-1-24_10-57-42.png

    The 5V blue point was missing, and some of the yellow points were also missing.

    So my guess might be the buck that died, and I don't need to replace any of the "problematic" chips .

    Any tips?
     
  2. JaapDaniels

    JaapDaniels GBAtemp Advanced Fan
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    sounds like it, just first remove the caps to see if the chip really is the problem and it's not one of the caps.
    could be the problem on it's own.
    if 5V/4V is missing then there's a great change it's the buck.
    it seems not every part get's it power supply, wwich is a good reason for any system to break startup before it starts.
    just hope there's no data corruption.
     
  3. dicamarques

    OP dicamarques Definitely not Bruce Wayne.
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    4V works, 5v doesnt.

    I still need to find someone with a hot air station around where I live
     
  4. JaapDaniels

    JaapDaniels GBAtemp Advanced Fan
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    i don't know to help you there, i know any alectronics repairshop around here has one, if there's an industrial closeby, i'd say there should be some shop... it's not that cheap but it's essential these days...
     
  5. CHTechRepair

    CHTechRepair Member
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    The shorts you are measuring on MAXX77621 aren't likely true shorts. I've gone over this a lot those rails are very low voltage and therefore very low impedance. A diode mode measurement can confirm a true short here. Follow my guide's solution #1 for tips on where to go when you have battery charging but no power at all. It becomes a goose chase quickly without a known good board to try and find issues. MAXX77620, SMC/Southbridge, GPU, and eMMC/Firmware are all likely candidates and there are few tests to confirm where the issue lies.
     
    Last edited by CHTechRepair, Jan 27, 2021
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  6. dicamarques

    OP dicamarques Definitely not Bruce Wayne.
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    Where should I measure the 0.8v to the cpu?
    Also this switch was previously altered to use the RCM
     
  7. notrea11y

    notrea11y GBAtemp Regular
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    Last edited by notrea11y, Jan 29, 2021
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