Summary
for an attempted repair.
At first inspection the device appeared to be basically unresponsive, with none of the four fans running and no signs of life other than a few lit LEDs on the main PCB after supplying power to it. After full disassembly and with no repair guide or schematics to go by [Mark] had to start from basics, first diagnosing whether all the power rails were turning on, which they weren’t.
Eventually this led to the NXP LPC11U6x-series MCU which acts as the main power management and monitoring chip in the system. [Mark] deduced that this MCU wasn’t turning on all the power rails because it was waiting for a signal from the fan controllers on the SATA backplane. With the MCU sending the right signals here, and the fans all working when directly supplied with power, ultimately it turned out that a single SI2319 or similar P-channel MOSFET in SOT-23 package near one of the fan connectors had gone faulty.
Replacing this one MOSFET seems to have fixed the RAID array, with it now happily powering up, although the real test will be once the [Slow Mo Guys] start shoving the HDDs back into it. Assuming that this was the sole fault in the system, then it was a very cheap fix in terms of materials. It’s a real shame that repair guides or schematics aren’t made available for devices like this, even if just after they stop being produced.
I imagine that I’m being misled by the appearance of what is basically the biggest model from a consumer, desktop, line that just looks a lot like a drive shelf; but I would not have guessed at that cause of failure.
I’m overwhelmingly used to IT gear definitely being touchy about the status of its fans; but quite specifically being willing to wake up far enough to scream at you in one way or another(blinking out an error code, audible alarm, or the BMC crying about the situation on whatever interface you prefer to check it through) about the fans.
I hope that having a hard refusal to boot doesn’t imply anything ominous about how much monitoring it is doing after it starts; because that would be the main reason I’d think of for treating one fan out of spec that drastically.
If I had to guess, it’s just a boot sequence “turn on fans → wait for fans on → continue” that doesn’t ever get the “the fans are on” signal.