I think my Teensy 4.1 is broken

D

Drodru

Member
My Teensy 4.1 does not work. When I connect it to my computer, nothing appears. I tried to measure heat, and the mosfet is really hot, but not the main chip. Does this have any type of solution?
 
Do you happen to have a multimeter? First I would measure the voltage on the Vin pin and 3V3 pin. Should be ~5V and ~3V3 respectively.
Is indeed FET Q1 getting hot or its neighbor U4 (the 3V3 regulator)? Details on the schematic and component locations at the bottom of this page.
Please also closely inspect the board for solder shorts. Is there any other circuitry connected to the Teensy 4.1?

Paul
 
Nothing is connected, just the USB. The 3V3 regulator is indeed the hot one. I measured the voltages, 4.8V in VIN and none in 3V3 (all with ground). 3v3 is shorted with GND. Do you think if we replace it we can solve it or its a bigger fail?
 
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Please give measurements in numbers, rather than "none in 3V3" - is this 0.00V, 0.0V, 0.1V ,0.5V? This level of detail is usually very revealing.

If its 0.1V or less I'd suspect a hard short somewhere, you have to find it and fix it - the regulator will be hot because of the short, so there's no point replacing the regulator until the short is found - do you have access to a thermal camera? Sometimes they can pick up on a small solder tail or something like that causing a short.

If its more like 0.4V or something like that the regulator might faulty, or some other chip, some more investigation will be needed, but it starts to make sense to replace the regulator.
 
If you have a DVM, disconnect USB cable and allow a few minutes for caps to discharge. Then use ohmmeter to measure resistance from 3V3 to GND. Like MarkT suggested, there could be a short to GND on the pcb somewhere. Replacing the regulator would be a waste of time. You will have to find the short. Most often one can find it with careful visual inspection.
 
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