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tetrabiodistributed / papra-pcba

Printed Circuit Board Assembly (PCBA) for the PAPPRa m12 controller
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Investigate blown rev .2 PCB #41

Closed mechatroniks-git closed 3 years ago

mechatroniks-git commented 3 years ago

At the end of the 4/10/22 build party, tested new IP rated DC cable, which had short, fried Mark's M12 control board.

mechatroniks-git commented 3 years ago

Powered up m12 board, found 5V regulator was hot and only outputting 1.4 VDC.

5V regulator has overcurrent and thermal protection, likely kicking in Downstream device likely shorting to ground.

Measured less than 10 ohms between 5V and ground, not good.

Lifted pin 1 of ATtiny (5V) and short went away, ATtiny is fried, will replace.

Looking at the circuit, it is very likely that a short condition at the DC jack can drive +12V into ATTINY thru the unused, but connected FAN-SENSE pin. Recommend we remove this connection. Same for GND-SWITCH.

mechatroniks-git commented 3 years ago

MOSFET also blown. Replaced, board is now working. Same failure mode, shorted output can fry the MOSFET and ATTINY. Will be resolved in V.5 of PCB, for now, don't short the output and you will be good.

ATtiny was replaced with 214, but 2K code space fills up, so had to remove startup knight-rider LED sequence to fit. Same issue likely with the 204 flavor. Also, v2.3.1 of the MegaTinyCore has a bug with this chip, created issue. V2.9 works.

darraghbr commented 3 years ago

It might be worth adding an eFuse IC? It would replace the polyfuse, and could provide overcurrent, overvoltage and short protection.

https://www.ti.com/power-management/power-switches/efuse-hotswap-controllers/overview.html?keyMatch=EFUSE&tisearch=search-everything

mmroden commented 3 years ago

closed by #43