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After the [Slow Mo Guys] acquired a 168 TB Seagate LaCie Thunderbolt 3-based RAID storage system back in 2019 to store their video footage, they were obviously slightly miffed when suddenly it would just refuse to power up. Naturally the device was now out of warranty, the product itself no longer produced and Seagate support was less than supportive, ergo they sent the device to [Mend it Mark] 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.
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