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I measured voltage using a multimeter between PP3-PP27 and it was fluctuating between 0.01V to 0.06V is this normal? The entire problem can be found here: USB ports recieving power but not working on Raspberry Pi 3B
Please help me resolve this issue

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  • You should add this information to your original question, instead of creating a chain of questions that are linked to each other. May 21 at 15:54
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    @LjmDullaart It makes less sense to unconditionally add information to a question if this means slowly morphing the question (which this does) into something that would invalidate existing answers. This is not information that anyone asked to be added to clarify the question. It's essentially a separate question. Note that neither of these is actually the first question by the OP in diagnosing the problem. He is proceeding logically through a problem that poses multiple questions something we discourage people from cramming into a single post.
    – goldilocks
    May 21 at 16:50
  • @goldilocks That's exactly my point. Thanks again :)
    – Kiran
    May 22 at 3:27
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    I realize the bit about invalidating answers where there were none sounded a bit daft, but it's about the practice: If the other question were "as is" problematic and required more information according to other users, then yes, taking that and asking a whole new question is counter-productive. But in this case it seems to me that the OP had come up with a conjecture about the nature of the problem that to be valid needed confirmation:
    – goldilocks
    May 23 at 14:21
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    It wasn't someone who knows what the voltage across PP3-PP27 should be, saying you need to check this and let us know what the value is, it is someone wondering about the possibility. So there is a fairly simple, straightforward independent question there -- albeit one which is (according to Milliways) currently unanswerable definitely -- which need not be tied down into the other, rather long and convoluted one. Which, again, encouraging people to break down long convoluted questions into shorter simple ones where possible is a good thing.
    – goldilocks
    May 23 at 14:21
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You are clutching at straws and attempting to follow magic answers.

The full circuit details of the Pi are not published so no one actually knows what PP27 is. It is possible to trace circuitry on a board (I have done this) but it is very difficult on a multi layer board.

I do not doubt that you have some problem but searching the web is not going to solve it.

Guessing from your earlier posts I expect that you have blown up the chip which controls USB power.

From memory the chip is programmed to provide 1200mA (controlled by a MOSFET on Pi2) which has inbuilt overload protection.

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  • So you suggest that I bin this board and get another one? I just want to be really sure before I do that
    – Kiran
    May 22 at 3:29
  • And this is how I knew what PP27 is for raspberrypi.stackexchange.com/questions/91901/…
    – Kiran
    May 22 at 3:36
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    @Kiran The Pi(3/2/B+) USB Current are supplied through a Current-Limited Power Switch (AP2553?) (U13), although this is not shown on the published schematics. This is someone's deduction and is unclear if this is input or output, but either way it is dead. You can find specs for the AP2552/ AP2553/ AP2552A/ AP2553A if you are interested.
    – Milliways
    May 22 at 6:37
  • Sure I'll look into that. So there is no way of repairing my RPi? Thank you so much for your help.
    – Kiran
    May 22 at 9:47

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