I've got a dead Hitachi HDD because of overvoltage (12volt). I plugged my external enclosure in with the wrong power supply. The enclosure is fine (checked it with other hard drive). The hard drive is dead and doesn't spin at all since then. By observation with bare eyes, it seems no physical damage to the PCB. After reading the forums, it looks like it maybe because of the TVS diodes.

Can someone help and tell me where my diode is? I will then test it with a multimeter, and if dead, will remove it just so the HDD spins up and I can get the data off.

Hard Drive:
HDD: 5k320-320
Model: HTS54323L9A300
Date: JAN-09


Here are threes pictures of the PCB :

Your drive does not get its power from the 12V supply, only the 5V.

Check fuse F1 and diode D1.

_________________
A backup a day keeps DR away.

Thanks so much.

Diode tests 2.35 OHMS...

The Fuse Tested as infinity (no connection) but it's hard to test because it's so small..

So I assume it's the fuse and not the Diode?

If the fuse tests bad can I just snip it out and will the hard drive spin up - or do I have to replace the fuse? Thanks.

The diode is shorted. Remove it and test it again.

If the fuse measures 0.0 ohms, then it is OK. I would measure its resistance again, this time using the F2 pads immediately alongside it. Scratch the solder if you need to get a better connection.

_________________
A backup a day keeps DR away.

Sharpened the Multimeter prongs and retested the fuse. The fuse tested as infinity (no connection).

Can i just remove the fuse or do I have to solder a piece of wire in there to replace it?

Before you do anything, remove the diode and confirm that it tests shorted out of circuit. Also confirm that the short is no longer present on the PCB.

I would also measure the resistances of the three capacitors in the attachment. This will tell us if the Vcore and Vio supplies are suspect.

_________________
A backup a day keeps DR away.

I removed the Diode with a pair of nail clippers. Solder remains, but the Diode has been removed.

The three capacities you circled in the above picture test as follows - from left most in the above picture to right most:

Bottom Left - 0.L (infinity - no connection)

Bottom Right - 3.68

Top Right Vcore - 0.07


Thank you for your help. Let me know how I should proceed.

You didn't say whether you are still measuring a short at the pads of D1 on the PCB and at D1 itself. However the Vio and Vcore measurements would suggest that the MCU is shorted (assuming you mean 3.68 ohms), so there would be no point in trying to repair the PCB.

Can you also measure the resistance between the two terminals marked with an X in the attachment? Do the same for the Y terminals.

_________________
A backup a day keeps DR away.