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Thread: Teensy 4.1 dead

  1. #1
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    Teensy 4.1 dead

    Well I had everything working like I wanted it and decided to try and power the Teensy from a 12v -> 5v buck converter on Vin. Not sure what happened, but the light does not come on anymore and the USB sound is not made like it usually does when plugging USB to my PC.

    I found a few test procedures on the forum
    - I'm getting 3.3v and 5v on their pins when powered via USB
    - Unpowered resistance from 3.3v to ground is only 33 ohms
    - 3.3v on the program pin doesn't change when the reset button is pressed

    Is there anything I can do to revive this thing? I've had it for a week!

    Thank you.

  2. #2
    Senior Member+ defragster's Avatar
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    Given no voltage drop on Program pin pressing the Button - then a 15 sec Restore Button press would fail as well if the bootloader chip is not seeing the button?

    But won't hurt to try: Press Button and at 13-17 seconds if seen the RED LED will flash saying to release the button to execute the Restore of Blink sketch.

    Supposing nothing on PCB feels HOT since the 3.3v and 5v measure properly?

  3. #3
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    I tried holding the reset button for 30 seconds and never saw the led flash.

    Nothing is hot, but the main chip does get warm.

  4. #4
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    After leaving it on USB power for a while to see how hot things get, I noticed a few components getting hotter than the rest.

    - The small square SMT chip next to USB Host D+ pin - 125 degrees F
    - The 2 PSRAM chips I soldered on the back - 160 F

    Does that tell me anything? Thanks for your help.

  5. #5
    Senior Member BriComp's Avatar
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    - The small square SMT chip next to USB Host D+ pin - 125 degrees F
    That's the 3.3V regulator.
    Perhaps take off the two PSRAM chips.

  6. #6
    Senior Member PaulStoffregen's Avatar
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    PSRAM chips don't consume a lot of power. The 3.3V regulator can easily power them up.


    Of the many things written here, this one seems extremely strange to me:

    Quote Originally Posted by formula349 View Post
    - 3.3v on the program pin doesn't change when the reset button is pressed
    Can you double check this? The pushbutton is wired to the Program pin and GND, so pressing it should directly short that signal to zero volts.
    Last edited by PaulStoffregen; 05-14-2022 at 05:14 PM. Reason: typo

  7. #7
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    You're right. I was looking at the pinout upside down...
    The program pin does drop to 0 when the reset is pushed, but only has 0.22v on it otherwise.
    I'm going to remove the PSRAM chips tomorrow and see if that helps anything.

  8. #8
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    Well removing the PSRAM chips did not make a difference.

    Why would I get 3.3v off the regulator but only .2v on the program pin?

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