Troubleshooting old HDD that doesn't spin?

1337Ox · May 17, 2021

Hello everyone, I would like to know your opinion on this.

So, I found my old 750GB WD harddrive (WD7500AAKS), which long time ago suddenly stopped working, it just wouldn't spin anymore.

And today I thought I might give it a try and possibly fix it? I am by NO means an expert on electronics but I think I might found the problem?

I think the problem is on the PCB, my suspect is a R100 resistor, which value should be 1 Ohm, and therefore it should read as continuous with my multimeter, but it does not.

By just looking at the PCB there doesn't seem anything wrong, burnt.

I will provide you with a photo.

I would be really grateful is someone could confirm, that this could be the problem causing the disk not to spin at all. Or if someone has another suggestion?

There is nothing super important on that drive, I am just curious if I could fix it.

WhitetailAni · May 17, 2021

Does the drive spin if you short R120 (the suspected problem resistor)?

1337Ox · May 17, 2021

Oh, I can do that without damaging something else? Also my bad, it is 0.1 Ohm resistor, not 1 Ohm, which seems like very small value to me.

mariushm · May 17, 2021

Desolder that resistor and see if it's 0.1 ohm

Also check the capacitors on the same traces with it ... check C57 , C68

You have a resistor there marked continous ... your meter is stupid, the resistor should be 0.05 ohm which is very low . Desolder it maybe and check.... but it's probably fine, would be bad if blown open.

R7 and R8 should be 1 ohm, not continuous.

Check C90 and C131 for shorts , both by the sata power connector. If they're shorted they could cause problems.

I think C131 is on the 3.3v side of the sata connector unless I'm getting confused ... if so, the hard drive may have implemented that STAND-BY feature, where if the drive gets 3.3v through one of the 3 3.3v pins, it stays in stand-by / sleep mode. Maybe use a bit of tape over those pins, or desolder the 3.3v pins completely and check.

Kilrah · May 17, 2021

If you're sure you're making good contact with that 0.1Ohm res and it's open then yes it's wrong and the resistor is probably burnt. Seems it might be there to measure the current consumption of the motor driver section, so if it's burnt the motor probably isn't getting power. Would see about replacing it.

29 minutes ago, 1337Ox said:

Oh, I can do that without damaging something else?

Should be OK, but it it burnt due to something else having failed down the line it could still damage stuff. Although there are fuses on the board so hopefully those would catch that.