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Hard Drive PCB repair

LoboX

Jul 23, 2013
5
Joined
Jul 23, 2013
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Hi all, i was searching on the forum for HDD PCB repair and i found nothing. I am trying to get power to this PCB so i can turn on the hdd and extract the data is a WD hdd usually when this happens is the TVS Chips 12v & 5v makes a short. so you need to remove them, so it can work again, i have removed the TVS Chip "Diodes" and still no power. I was searching and found another PCB i test the good PCB and it works on the hdd it gives power to the drive, now i know the drive is working but i need the original PCB to extract the data. I was testing here and there, and found with my multimeter that those points on the good PCB they beep on the bad PCB it doesn't beep, so what could be the problem there?

The third picture i just want to know what are those? Since the circuits of a hdd pcb is kind of different from other electronic parts i have seen on a LCD monitor or PC motherboard, any help would be great thanks.
 

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Raven Luni

Oct 15, 2011
798
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Oct 15, 2011
Messages
798
The best thing to do is try and get a board from an identical drive. Or if you want to be hard core you can try getting the 1s and 0s off the disk. I remember reading a bit about the encoding years ago. Its basically done in such a way that the polarity is always alternating and its the length between and 2 states that determines a 1 or a 0 - its done this way since having long sections of any 1 polatiry would be much more prone to magnetic degradation and interference.
 

LoboX

Jul 23, 2013
5
Joined
Jul 23, 2013
Messages
5
Yes i know if i do that i need to remove the ROM from the bad PCB and add it to the new PCB, but right now i am focused checking why i am not getting power to the PCB, before i buy a identical PCB.

Thank you for your suggestion.
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
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Nov 28, 2011
Messages
8,393
Have you checked the fuses? There's one on the left, at a 45 degree angle, and another near the top. When the TVS goes short, high current flows and this will blow the fuse. At least it's a possibility.

The components you've highlighted in green are "zero ohm resistors" aka links. They should measure short circuit.

The components highlighted in yellow are multi-layer ceramic capacitors ("MLCCs").
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
Check the fuses for resistance from one end to the other. A fuse should read zero ohms if it's OK. If you measure any significant resistance (i.e. more than you measure with the probes shorted together), the fuse is blown.

Yes, zero ohm resistors should measure short circuit, i.e. zero ohms.

That's a very good article you have linked to.

One thing it mentions is that the zero ohm resistors may be used as fuses. It mentions this in relation to Western Digital drives. In any case, you should check the zero ohm resistors as if they were fuses.
 
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