Hello everyone. Last week the PSU in my fileserver starting acting up so the server was shutting down every 10 or 15min. The failure seem to have hit 6 of my 8 drives. The drives are not spinning anymore. They all have the same board like in the picture. They all have a identical fault. What is weird is that the two surviving drives are more recent with pcb made in Taiwan and the 6 faulty ones have pcb made in China and are two year older

-As of now I have tested the fuses and diodes near the power connector. They all tested good.
-I also tested the voltage at the input and output of both E-Switch and I got 12v and 5v at input and output pins.
-Just for testing I try swapping a good board from a spare drive I have. Same model. Drive spin with the good board but since I didn't swap BIOS chips it is not recognize by the computer.

Can someone guide me to what else I could test on the board. Thank you

I'm wondering whether the non-volatile cache (if it exists) in the ROMs is corrupt? Modern drives incorporate power loss data protection, and data is backed up in NVcache. I don't know whether your model is one of these. Another complication is that some models have unique keys in the MCU, which means that you would need to transfer both the MCU and the ROMs to a donor PCB, if you decide to go down that path.

On the hardware side, my next step would be to measure the voltages around the SMOOTH motor controller.

_________________
A backup a day keeps DR away.

Measure the voltages at the marked locations. In some cases I've boxed the entire component because I can't tell which end is grounded.

_________________
A backup a day keeps DR away.

Here are the voltage readings from each location.

Those voltages seem OK, although I confess that I don't understand the function of all of them. The fact that the -3V supply for the preamp is present would suggest that the MCU is talking to the SMOOTH motor controller, so the digital logic seems to be working.

Can you measure those same voltages on your working donor PCB?

_________________
A backup a day keeps DR away.