Does anyone know a reason why the digirig would fry itself while left plugged in over night while the radio was off? I am even more confused because whatever the issue was caused both the digirig and raspberry pi to become completely unusable.
my ‘guess’ is that there was insufficient grounding of either PC, radio, or both.
the go juice found a path to ground via the digirig.
again, just my guess
good luck
kb0wlf
From what web research has to say, the failures in RPi’s MXL7704 PMIC are most common from either wrong connections of 3.3V rail or supplied power. Digirig only takes 5V from the USB so it’s either caused by some other periphery using 3.3V or the power supply.
Here are the relevant details:
The MXL7704 PMIC is a common failure point on Raspberry Pi boards because it is highly sensitive to certain electrical mistakes. While it doesn’t usually “blow up” with a physical explosion, it can burn out internally, often leaving a small scorched mark or a “magic smoke” smell.
The most frequent causes for this chip to fail include:
Electrical Shorts
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5V to 3.3V Short: This is the most common “death sentence” for the chip. If you accidentally bridge the 5V and 3.3V pins on the GPIO header (for example, with a metal screwdriver or a slipped multimeter probe), the PMIC will immediately try to “clamp” the excess voltage. This process typically destroys the internal 3.3V regulator, permanently bricking the board.
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3.3V to Ground Short: Directly shorting the 3.3V rail to ground can also cause the chip to overheat and burn out as it tries to provide current to a dead short. [1, 2, 3, 4, 5]
Power Supply Issues
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Overvoltage: Using a “dumb” power supply or a cheap buck converter that fails can send more than 5V into the board. The MXL7704 is not designed to handle high voltage spikes and will often fry instantly if it sees anything significantly above 5.1V.
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Polarity Reversal: On Pi Zero models specifically, accidentally reversing the polarity of the power input can destroy the PMIC and the main SoC. [6, 7, 8]
In an earlier post, I documented odd behaviour of the digirig when the radio was off. I haven’t posted that much here, so you might be able to find it. The point, IIRC, was that the digirig seemed to be in an uncertain state until the HT was turned on. While I can’t see how that might have caused /this/ failure, it does point in my mind to a possible failure mode due to being in an uncertain state.