Teensy 4.1 3.3V shorted with GND and a chip part is broken

liudr

Well-known member
So I've used this board for a couple of months without issues. I wanted to connect to Serial1 so I soldered two rows of headers to it. Coincidentally after soldering on the headers the device stopped working. I touched it and it almost burned me. I measured with a USB power meter and it is pulling 500mA of current. I tested the pins. 3.3V now shorted to GND. I also discovered a broken chip resistor or else on the back side, near the host pins. I'm pretty good with soldering irons and reflow ovens. I could find no faulty soldering job but I wonder what that broken chip was, which could help me understand what happened and whether I could repair it.
Screenshot 2022-03-25 205536.jpg
 
It seems like resistor R8 is broken. From the bottom of this page:

Capture.PNG

Its value is 100kΩ and it pulls down the enable signal from the processor to the TPD3S014 current-limit switch for the USB host power. See the schematic on the same page.

With respect to the 3V3 shortened to GND: please do a close visual check (again) for small metal particles or solder balls.

Paul
 
Thanks PaulS. I checked over and over. I saw no solder jumpers or balls or else. Is it possible that static electricity may have destroyed the output capacitor of the 3V3 regulator and it's shorting? I don't have time to spend on this board now. I'll later remove the regulator and test again. Will need small hot air gun nozzle for this ;)
 
Back
Top