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Thread: Damaged my Teensy 4.0 :-(

  1. #1
    Junior Member
    Join Date
    Jan 2020
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    9

    Damaged my Teensy 4.0 :-(

    Hi,

    I think this is my own fault.

    I was trying to go cheap, didn't have any long-tailed female pin sockets.
    So I used some stiff copper wire for pins.
    But that lead to hard insertion force into my project board.
    And hard removal too. I think that's when I did it.

    When I applied power nothing happens.

    Just between pin 11 and the reset button there are two small devices.
    The one next to the button looks munched. I must have pried against
    it I suspect.

    So I need to order another Teensy 4.0.

    While I'm waiting for that, could someone tell me what that device is?
    Maybe I have one or something that would substitute.
    Yes it is small. I have a microscope and the board is DOA,
    so why not give it a try.

  2. #2
    Senior Member PaulStoffregen's Avatar
    Join Date
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    21,319
    Quote Originally Posted by ChrisHoward View Post
    Just between pin 11 and the reset button there are two small devices.
    The one next to the button looks munched. I must have pried against
    it I suspect.
    That part is this diode.

    Click image for larger version. 

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    If the other diode and nearby parts are still ok, maybe try adding a coin cell or an external 3.3V power supply to VBAT. This diode is only needed for the chip to boot up (power on the VDD_SNVS_IN pin) which causes it to turn on the main 3.3V regulator. If you add 3.3V on VBAT (add it while the rest of the board is unpowered), maybe you'll be able to make use of this damaged Teensy.

    You could also try putting 3.3V directly onto the 3.3V pin. But that will only work if the 3.3V power has a fast startup time, like a physical switch. VDD_SNVS_IN needs to get power before or at worst case together with the rest of the chip. If externally applied 3.3V rises too slowly (as many power supplies do), the chip will see power at other pins before VDD_SNVS_IN, due to the diode drop. The chip only boots if VDD_SNVS_IN is powered first, which is why Teensy 4.0 has this diode circuit and the main 3.3V regulator is enabled by the chip's power management.

    If more stuff if broken, then that board is probably a complete loss. But here's at least a couple simple things to try to make use of it without that broken diode.

  3. #3
    Senior Member
    Join Date
    Aug 2017
    Posts
    172
    Quote Originally Posted by ChrisHoward View Post
    Hi,

    I think this is my own fault.

    I was trying to go cheap, didn't have any long-tailed female pin sockets.
    So I used some stiff copper wire for pins.
    But that lead to hard insertion force into my project board.
    And hard removal too. I think that's when I did it.

    When I applied power nothing happens.

    Just between pin 11 and the reset button there are two small devices.
    The one next to the button looks munched. I must have pried against
    it I suspect.

    So I need to order another Teensy 4.0.

    While I'm waiting for that, could someone tell me what that device is?
    Maybe I have one or something that would substitute.
    Yes it is small. I have a microscope and the board is DOA,
    so why not give it a try.
    Looks like you may have crunched a diode for VBAT or VDD in. There are two diodes one for VBAT and one for VDD (3.3v) from the voltage regulator. Probably steering diodes. Either way if the diode for VDD is inoperative then the Teensy will not power up. You could check the BOM for the T4 and replace the the broken diode with the appropriate part.

    Does anybody know if there is a BOM for the T4. I thought I saw one but maybe it was for something else. They are very small and I am not sure if they would be easy to replace

    Edit: Had the wrong diodes
    Last edited by wwatson; 01-26-2020 at 04:41 AM. Reason: Wrong diodes

  4. #4
    Junior Member
    Join Date
    Jan 2020
    Posts
    9
    Putting voltage on VBat(+)/Gnd(-) did the trick!

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