WD5000AAKS PCB burned component

WD5000AAKS - 00TMA0. Burned capacitor(?) C12. There is black gunk on one end of it and even a burn mark on the soft padding material.

Perhaps I could try to replace the part if I knew where to get one.

That looks like an MLCC capacitor (Multilayer Chip Ceramic). I don’t know what it does in your circuit, but you should be able to determine whether it connects to either of the +5V or +12V supplies. If so, then you could probably run without it. Otherwise it could be involved in emergency retract, in which case you should replace it.

Multimeter pointer moves with both +5V and +12V pins and the C12 end that is facing C6. Other end doesn’t connect.

I forgot to describe the symptoms. The drive is recognized by BIOS and OS, but any read/write attempt hangs.

Your measurements are vague, but it appears that the junction of C12 and C6 connects to ground, and the other end is unrelated to either the +5V or +12V supply. In any case, the capacitor is not shorted.

That said, I can’t see how C12 would produce the symptoms you describe. If the drive is detected with its correct model number and capacity, then this means that it is able to spin up and read the reserved System Area on the platters.

Are you able to access the drive’s SMART report? Can you see its partitions in Disk Management? If not, could the drive be password protected?

Any app that tries to read SMART as well as Disk Management just freezes.

No password.

Actually I can see the drive in Disk Management if I don’t try accessing SMART first. DM wont do anything to the disk though, just gives various erros.

Virtual Disk Service logs error: A failure was encountered while retrieving the volume properties. Error code: 0x80070002@020A000D

I believe C12 may be the “boost” capacitor that provides a boosted supply voltage to the voice coil circuit. If you disconnect the board from the drive and power it up on its own, I expect that you should measure about 18V across the pins of C12.

That said, the WD5000AAKS is a “Tornado” model. This model has an 88i6745 Marvell MCU that is afflicted with a fault that mimics head or media problems.

If you wish to replace C12, and if the voltage across it is indeed 18V or so, then replace it with a 330nF MLCC capacitor. That’s the value in the application circuit in the datasheet for the L7250 SMOOTH motor controller (not the same as yours, but probably similar).

L7250, SMOOTH, spindle motor + VCM controller, ST Microelectronics:
http://wandrew.regruppa.ru/PCInfo/TechDoc/L7250(Smooth).pdf
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXyuswx.pdf

If that doesn’t fix it, and if you would like to try a board swap, then you will need to transfer the board’s unique “adaptive” data to your donor PCB.