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Thread: Teensy 4.1 faulty voltage regulator?

  1. #1

    Teensy 4.1 faulty voltage regulator?

    My 2 week old teensy was working before, however, often when i did a reset the small red led came on and nothing happened. The uploaded sketch would not run.
    But after disconnecting the power and plugging it in again, it would work.

    Tonight this happened again, but when i plugged it back in...... Nothing!

    No led, No small red led. No running sketch!

    After connecting it to USB (usually use it with the VIN) it wouldn't work either. So i took my multimeter and measured the VIN pin which gave me 5V.
    Then i measured the 3V pin (almost next to the VIN pin) and it gave me 0.48V. So i measured the other 3.3V pin and it gave me 0V.

    I measured the pins of the voltage regulator on the teensy and only one pin gave me 2.68V

    So i think i have a faulty regulator. Am i right?

    I have been very cautious not to overpower/over-voltage the teensy with external power. I never used USB AND external power together.
    It seems not to be my fault so can i apply for a replacement?

  2. #2
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    Quote Originally Posted by Mano1979 View Post
    My 2 week old teensy was working before, however, often when i did a reset the small red led came on and nothing happened. The uploaded sketch would not run.
    But after disconnecting the power and plugging it in again, it would work.
    Mano1979:

    I can't speak for whether you have a failed regulator or not, but I wanted to provide some clarifying info WRT one of your statements. The button on the Teensy is a "programming" button, not a "reset" button. When pressed, the Teensy enters "programming mode" (waiting for a download over USB). Additionally, holding the programming button should result in a quick flash on the red LED after ~15 seconds. Releasing the button should then do a full flash erase and restore to a known-good LED blink program. You might try this to see if you can revive your Teensy this way.

    Good luck & have fun !!

    Mark J Culross
    KD5RXT

  3. #3
    I tried to push the button for 15 seconds and more, but it does nothing. i even found that the square chip closest to the usb port get's warm when i plug it in.
    i know the button is not a reset button, (allthough it is called that quite often all around the web) but it does work that way. the program restarts after pressing the programming button.
    Though i see now why the red led came on and the sketch would not run.

    Thank you for your reply!

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by Mano1979 View Post
    Then i measured the 3V pin (almost next to the VIN pin) and it gave me 0.48V. So i measured the other 3.3V pin and it gave me 0V.
    Usually this means something is shorting the 3.3V power to GND. The voltage regulator gets hot because it's trying to deliver as much current as it can. Fortunately, it has a thermal protection built in which limits how much it will output. There is also a 500 mA PTC fuse (which is really just a low-ohm resistor which grows in resistance as it gets hot) which also serves the limit the current when things go wrong. The regulator and PTC fuse are almost never the problem. They get hot because something else is going horribly wrong, trying to short out the power supply.

    These problems are tough to diagnose. But the fact that you're seeing different 3.3V-to-GND voltages is a good sign. That makes it easier to find the problem. The "closer" you are to where the short is happening, the lower the voltage you'll measure. You'll see slightly higher measurements "farther" away, because the large current is traveling through wires or ground planes which do have some resistance and cause a small voltage change. It can take a little intuition or guesswork about where the current is actually flowing, but generally when something is directly shorting the power, you'll see little or no voltage near the problem.

    Zero volts is a good sign. That usually means the short is wire or something metal. Measure something like 0.6 volts or more often means the short isn't a good conductor. Often those types of shorts happen inside the chips, usually because they were destroyed by some condition like touching 5V power to the 3.3V power line or the signals which aren't 5V tolerant. Obviously if the short is a damaged chip, there little hope of repair. But if the short is a wire that somehow got connected between 3.3V to GND, the good news is a Teensy almost always survives that sort of problem once you find and remove it.


    I tried to push the button for 15 seconds and more, but it does nothing.
    Yup, when you don't have 3.3V power, the button won't do anything. The MKL02 chip runs from the 3.3V power supply, so you can expect it to not work until you have proper power again.

  5. #5
    The problem is that there is nothing connected to the teensy. i removed it from the project. and it used to work, but suddenly stopped working without any changes...

    So i can assume it is dead... is there any guarantee? i mean can i get a replacement? i guess it is not normal if a teensy fails within 2 weeks right?

  6. #6
    By the way, there seems to be a short between GND and 3.3V. but not externally. so it must be in the voltage regulator right?

  7. #7
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by Mano1979 View Post
    By the way, there seems to be a short between GND and 3.3V. but not externally. so it must be in the voltage regulator right?
    Shorted power is almost always somewhere other than the regulator, but the regulator gets hot because it is trying to deliver maximum current into the short.


    Quote Originally Posted by Mano1979 View Post
    i guess it is not normal if a teensy fails within 2 weeks right?
    All sorts of problems and mistakes are quite normal with soldering and connecting external circuitry. If 5V or higher voltage is accidentally touched to the 3.3V power, or to pins which aren't 5V tolerant (all the I/O pins on T4.1), the chips can be damaged in a way that is similar to a 3.3V power shorted to GND.

    The main question is whether the board was working when it arrived, if it was in working condition before connecting other stuff.

  8. #8
    I agree to a certain extent. Components like transistors, mosfets and voltage regulators, do tend to short when they break. There is nothing connected to the teensy and the short is still there. And nothing changed since it whas working before.

    And yes, it worked when it arrived, but it has been a bit fuzzy since the beginning (see first post).
    No 5V touched the 3.3V logic pins. I am very carefull with those things and i have a degree in electronics engineering, so i know my way around electronics (for over 30 years now).

    The simplest conclusion is that there was a bad component in the batch (which happens) and that it gave out with the slight use i put it through.

    I understand that it's easier to think that the user did something wrong, hence braking the teensy, but i'm quite sure this whas not my fault.

  9. #9
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    Did you inspect the Teensy with a magnifying glass and good light?
    Sometimes with these dense ciruits a tiny stray solder bead or a tin whisker can lock it all.

    A latched-up CPU can happen not only by touching 5V. even an ESD massive enough could kill the Teensy, because the internal ESD protection has limits.
    Dry weather or air conditioner and a synthetic fabric or carpet somewhere?

  10. #10
    I did inspect it with a loupe (with build in light) and didn't see anything.

    I know ESD can be a problem, that is why i always discharge before handling any electronics. But i'm sure i didn't touch it between it working and it stopping tot work.

  11. #11
    Senior Member PaulStoffregen's Avatar
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    Can you show us photos of this problematic Teensy 4.1?

  12. #12
    Sure you can download them here:
    https://we.tl/t-w48fGvd8xZ

  13. #13

  14. #14
    Senior Member PaulStoffregen's Avatar
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    Was this Teensy 4.1 purchased directly from PJRC, or through a distributor?

    If it came directly from us, please email me or Robin with the 6 digit order number and a link to this forum thread. If you no longer have the 6 digit order number, we can try to look it up, but we'll need info like your shipping address and the approximate date of the order.

  15. #15
    It whas ordered from a distributor. TINYTRONICS.NL
    Does that mean i have to take this up with them?

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