Help on an Overvoltage Failure/Repair

[will5001]

You can scrape away some of the area around the test points to expose the copper.

Takes a while to settle the readings.

Bottom pair seem to settle on 92 k ohm

Top pair more difficult to get a repeatable reading - seems to settle on 0.6 M ohm

[will5001]

Sorry for multiple posts. Just realised you asked to test it connected to HDD.

Top pair now rock solid and repeatable at 60 k ohm

Bottom pair now take a while to settle on 106 k ohm

EDIT - of course - diodes in circuits so it changes depending on which way round the probes are!

Bottom pair with red on ground 1.01 k ohm

Top pair 3.8 M Ohm

Maybe I've been staring at a multimeter screen too long and it's late

[fzabkar]

The preamp is not shorted.

Can you measure the resistance of each of the capacitors near V2? If a capacitor is shorted, then that would be bad news.

[will5001]

The preamp is not shorted.

Can you measure the resistance of each of the capacitors near V2? If a capacitor is shorted, then that would be bad news.

Doesn't appear to be any shorted capacitors. (multimeter on continuity and I tested basically all the components I could around V2)

[fzabkar]

I'm confused. Let me get back to you later.

Normally if one end of an inductor is grounded, this would suggest that it is part of a negative converter, in which case the other end of the inductor would be connected to the cathode (striped end) of a nearby diode. However, the nearest diodes appear to be associated with a different inductor.

[will5001]

Thanks for all the help - it's really appreciated.

[fzabkar]

Sorry, I don't understand what is going on in that area. It's probably safest to get a replacement PCB from a supplier such as hdd-parts.com and let them transfer the "ROM".

[will5001]

Cool - thanks for the help!

[will5001]

I thought I would take the risk and power it up! Foolhardy I know.

However - drive spun up and is recognised by windows. I'm now transferring the data.

Thank you for helping me out!

[fzabkar]

I think that V2 may be associated with the negative DC-DC converter for the preamp, in which case the diode would be inside the motor controller IC. If so, then this would be consistent with a grounded inductor.

In short, I believe that bridging the fuse (after removing the TVS diode) would be all that would be required.

The PCB in the following thread appears to be similar in this respect:

https://forum.hddguru.com/viewtopic.php?f=1&t=41021

The topmost inductor (is it actually a transformer?) might produce positive and negative supplies for the piezoelectric microactuator, but that's just a wild guess.