marcocipriani01
Member
Unfortunately, my new Teensy 4.1 broke because of a short circuit from 3.3V to GND. I connected a HX711 load cell amplifier the wrong way around, so VCC was connected to GND and GND to 3.3V (those damn DuPont connectors!). Other than that, there were two GPIOs connected to the HX711 data lines and the whole board was powered exclusively from the 5V pin. This bad connection caused the HX711 chip to short itself, so now if I measure resistance between VCC and GND I get ~10Ω. A busted HX711 is not a big deal, but this also forced the 3.3V Teensy output to ground. This event only lasted 5-10 seconds, because I noticed the over-current protection on my 5V power supply had tripped and the Teensy was not blinking. Nothing was hot to the touch and there was no magic smoke. I removed the HX711 and connected the Teensy to the PC, but no luck. It was dead.
Today I bought a reflow station and removed the NCV8186AMN330TAG 3.3V regulator from the Teensy 4.1, because that's what is likely to have broken. I connected the Teensy to the PC with a USB cable to give it 5V, then I powered the 3.3V line with a regulated power supply (in this order to comply with the power-up sequence suggested here). Sadly, the board didn't power up again. It consumes about 200mA at 3.3V, the MIMXRT1062 chip is fairly warm and the computer detects nothing. I ordered a new NCV8186AMN330TAG from Mouser but my hope is mostly lost for this poor Teensy (unless someone knows what else to do).
Now, however, I would like to understand why the Teensy was killed by a simple short like that, so hopefully it won't happen again - and next time I'll make sure to use JST-XH instead of DuPont. The Teensy 4.1 has a 500mA polyfuse and the voltage regulator is rated for 1A. I don't think the polyfuse protected the board at all because the 5V power supply's current limit was set to 1A, and it was maxing out since the overcurrent/short indicator was on. This is weird, but I have no other explanation. The MIMXRT1062 built-in voltage regulation shouldn't be broken because it's completely independent from the 3.3V line. A short on that line shouldn't even break the main or bootloader MCUs, they just wouldn't power up. Same for the ethernet and USB host chips. Despite all this, the Teensy seems lost forever. If you have any insight on what might have broken, please let me know. I'd like to turn this event into a learning experience for the future.
Today I bought a reflow station and removed the NCV8186AMN330TAG 3.3V regulator from the Teensy 4.1, because that's what is likely to have broken. I connected the Teensy to the PC with a USB cable to give it 5V, then I powered the 3.3V line with a regulated power supply (in this order to comply with the power-up sequence suggested here). Sadly, the board didn't power up again. It consumes about 200mA at 3.3V, the MIMXRT1062 chip is fairly warm and the computer detects nothing. I ordered a new NCV8186AMN330TAG from Mouser but my hope is mostly lost for this poor Teensy (unless someone knows what else to do).
Now, however, I would like to understand why the Teensy was killed by a simple short like that, so hopefully it won't happen again - and next time I'll make sure to use JST-XH instead of DuPont. The Teensy 4.1 has a 500mA polyfuse and the voltage regulator is rated for 1A. I don't think the polyfuse protected the board at all because the 5V power supply's current limit was set to 1A, and it was maxing out since the overcurrent/short indicator was on. This is weird, but I have no other explanation. The MIMXRT1062 built-in voltage regulation shouldn't be broken because it's completely independent from the 3.3V line. A short on that line shouldn't even break the main or bootloader MCUs, they just wouldn't power up. Same for the ethernet and USB host chips. Despite all this, the Teensy seems lost forever. If you have any insight on what might have broken, please let me know. I'd like to turn this event into a learning experience for the future.