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Thread: One Component on Teensy 4.1 gets very hot

  1. #1
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    One Component on Teensy 4.1 gets very hot

    Hi there,

    My teensy 4.1 used to work perfectly but, just now, when I plugged it in to the computer and tried to upload code I got the following error:

    No Teensy boards were found on any USB ports of your computer.
    Please press the PROGRAM MODE BUTTON on your Teensy to upload your sketch.

    I tried pushing the button, restarting my computer, and using a different usb cable. Nothing helped. I then noticed that one of the components on the board gets very hot very quickly when it is plugged in. Does that mean that the board is ruined beyond repair? I don't know which component is which. I am including a picture of which component is getting hot.
    Click image for larger version. 

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  2. #2
    Senior Member PaulS's Avatar
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    You may want to check out this thread.
    Most probably something [bad solderjoint?] is shorting the 3V3 output.

    Paul

  3. #3
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    Thank you so much for the quick response. I did not solder anything on the teensy board, and it worked well when I first bought it. How would I find a bad solderjoint? Is it possible to fix it or do I need a new board?

  4. #4
    Senior Member PaulS's Avatar
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    First I would do a visual inspection using an optical magnifier. Check for loose/missing/shifted/misplaced components. Also check for tiny solderballs/metal particles anywhere that may short signal lines.
    Don't forget to check the bottom side as well.
    Then using a voltmeter, measure the actual voltage between the 3V3 pin [marked "3V" on the PCB] and GND pin.

    Paul

  5. #5
    Senior Member PaulS's Avatar
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    Is it perhaps possible to send a close-up photo of your board?

    Paul

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    Click image for larger version. 

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    Click image for larger version. 

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  7. #7
    Senior Member PaulS's Avatar
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    The little wire in the red circle is not supposed to be there:

    Click image for larger version. 

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    Paul

  8. #8
    Senior Member PaulS's Avatar
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    Is the top of the package of the chip in the yellow circle nicely flat? It looks like a little bulge is sticking out. If so, then the regulator might be killed.

    Click image for larger version. 

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    Paul

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    Thank you for noticing that. I removed that wire and tried again. However, I am still having the same problem. The same component is getting hot and the computer cannot find the teensy. However, I am not noticing any bulge in component. Do you think it might be dead anyway? Is there a way to fix it?

  10. #10
    Senior Member PaulS's Avatar
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    Before concluding that the regulator and/or board is killed, you could do 2 more tests:
    1. with the USB cable connected measure the voltage between the 3V3 pin [marked "3V" on the PCB] and GND pin. If it's not around 3V3, there is some short between these pins.
    2. without the USB cable or other power supply connected, measure the resistance between the 3V3 and GND pin. My Teensy 4.1 measures around 8.3KΩ.

    Paul

  11. #11
    Senior Member PaulS's Avatar
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    Oops, sorry, I mixed up Teensy 3.2 and Teensy 4.1. The chip that is running hot is the MKL02Z32VFG4, the so-called Bootloader chip.
    That chip should not get hot as far as I know.
    Please forget the what I said and asked above.
    Not sure what to do next, perhaps replace the chip? But it would be sensible to get to the cause of running hot first.

    Paul

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    Would it make sense for me to mail the chip back to the factory then?

  13. #13
    Senior Member PaulS's Avatar
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    The problem is that little wire that you removed from the board. That could have been around the board anywhere and may have shorted out some other lines with a failing board as result. Normally this is not covered by warranty. And as you stated in your first post, the board used to work perfectly...
    It happened to me long time ago with a non-Teensy board as well - also a little piece of wire/solderblob lying around the board. I just wrote the board off as my own error.

    Mailing the chip/board back to PJRC for repair is not economical I assume.

    Paul

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    If it is helpful, I just noticed a second component that is getting hot. It is circled on the pictureClick image for larger version. 

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  15. #15
    Senior Member PaulS's Avatar
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    That's the DMG2305UX, a P-channel enhancement mode MOSFET that is setup to function as a low voltage drop diode. It carries the 5V USB voltage to the 3V3 regulator. That FET should not get hot at all.
    Hmm, I'm afraid the board is end-of-life...

    Paul

  16. #16
    Senior Member PaulStoffregen's Avatar
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    Very unusual for either of those 2 parts to get hot.

    Usually when things go wrong, the PTC fuse (small white part near the USB connector and 3V pin) gets hot. The voltage regulator (6 pin part just above the center pin of the USB host pins) also tends to get hot if something is shorting the 3.3V power. Those 2 parts are right next to the 2 parts you indicated as heating up....

  17. #17
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    Quote Originally Posted by PaulS View Post
    I'm afraid the board is end-of-life...

    Paul
    To me "end of life" means "no longer manufactured". I'd just say the boards fried!

    [ To "end of life" in the industry means to set a schedule for the phasing out of a particular device's
    production. Often seen as "That part's been EOL'd". Before that, if you are lucky, you'll see "no longer
    recommended for new designs" slapped over datasheets and search results. ]

  18. #18
    Senior Member PaulS's Avatar
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    I know EoL well, I should have said end-of-its-life... :-)

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