toshiba harddisk pcb repair

[BucketBoss]

Hi there, recently one of my harddisks stopped working. it spins up but wont appear in bios, desktop and so forth. i have a replacement pcb from an identical hdd but when i swapped the pcbs the old disk with new board didnt work nor did the new disk with the old board. i set the voltmeter to continuity and tested some of the smts, which i think were diodes, on both boards and found one (highlighted) on the old non functioning board that reads 0.345 and the corresponding smt on the new board reads 1.121. To me it seems like this is the faulty component and replacing it should fix the harddisk but my electrical knowledge only goes as far as knowing which way batteries go in a torch. As long as this is the only problem does it sound like this will work? any advice is greatly appreciated.

[fzabkar]

http://www.hddoracle.com/viewtopic.php?f=56&t=2600

[BucketBoss]

picture didnt upload. here it is

[BucketBoss]

oh

[Gyro]

That looks like one of the supply rail TVS protection diodes, possibly damaged by a surge. A simple continuity test doesn't really give meaningful results - it needs to be tested as a zener diode, or at least using the diode test function to see if it is shorted. Your continuity test does seem to indicate some sort of difference though.

Simply replacing it might solve the problem, but as explained in fzabkar's link, it might be too late for that now if the 'parameters' / fw area of the HDD has been corrupted.

It might still be worth a try though, you've nothing to loose at this point.

[testpoint1]

if no motor running, as usual, it is power supply problem, just check it.

[Gyro]

Good point. It would also be useful to know whether the spindle motor spun up with the other PCB (don't try it again!). If the disk didn't spin then it wouldn't be possible to corrupt anything. It would also make the reason more puzzling though.

[magic]

FYI,

it spins up

I wouldn't worry much about data corruption if the problem is clearly electric in nature, i.e. short from 5V to ground.

OP, check with a continuity tester if the "north" end of that diode is connected to ground ("south" is clearly at 5V). So far everybody's guess is that it's a TVS and therefore the other end should go to ground.
If so, remove it, switch DMM to diode mode and take a measurement with red probe on the 5V end of the TVS and black on ground. It should come the same as on the other disk with good TVS.
Also, check resistance of this blue thing which connects the TVS to 5V, it probably is some kind of resettable fuse.

[orbanp]

Here is my experience with hard disk repair:
https://www.eevblog.com/forum/repair/hard-disk-recovery/msg1310786/#msg1310786

I guess I was lucky.

Regards, Peter

[fzabkar]

The OP's drive spins up -- it just doesn't identify itself. This means that the PCB is most probably OK. The problem is most likely an internal one, possibly a corrupted or unreadable grown defect list or SMART module.

[FrozenHaxor]

From experience when those diodes fail, it shorts out the entire 12V line, most likely incompatible firmware between boards. You can try swapping the EEPROM chips from old board to the new and trying it that way, would help if the controller is dead, but unfortunately its most often that the EEPROM itself actually goes bad. Chances are nix.

[fzabkar]

The part number on the PCB (OA90380) indicates that the drive is a rebadged Hitachi. The problem is still most probably an internal one.

https://sep.yimg.com/ay/yhst-14437584971410/91711045-6.gif
https://www.hdd-parts.com/17110832.html