MK6026GAX does not spin

[D_R]

Hi,

I currently have a MK6026GAX on my desk, that isn't spinning. I have another MK6026GAX, that is working. The drive was dropped. On the damaged drive, I have a short between the motor supply pins and gnd. But even with the PCB from the working drive, the drive isn't spinning up. Do I also have to transfer the ROM from one PCB to another to get it spinning up? Or is it another problem?

BTW. the drive was opened before I got it, I don't know, what was done to this drive.

[pcimage]

Is there any noise from the drive at all?

Some buzzing or some other noise?

[D_R]

There is some little noise from the drive. It sounds like someone is accelerating with his bike. I recorded it for you. The first click you hear is from my mouse applying power to the HDD.

https://db.tt/A4YtAXiH

[fzabkar]

Is this one of those models with a sticky bearing?

Is the short at the motor itself (with the PCB disconnected) or on the PCB?

[D_R]

I checked the PCB without motor.
On the defective drive and on the working one I get nearly the same resistance between all pads of 7-11 Ohm.

[pcimage]

I'd say heads are stuck to the platter.

[fzabkar]

The OP says that "I have a short between the motor supply pins and gnd". Assuming that "gnd" is the metal body of the drive, and assuming this short is at the motor itself, then there is a problem with the motor windings. In such cases there may be a solution involving isolating the metal body from PCB ground and allowing it to "float".

[fzabkar]

I checked the PCB without motor.
On the defective drive and on the working one I get nearly the same resistance between all pads of 7-11 Ohm.

What resistance do you measure between the metal body of the drive and each of the motor pins?

[pcimage]

The OP says that "I have a short between the motor supply pins and gnd". Assuming that "gnd" is the metal body of the drive, and assuming this short is at the motor itself, then there is a problem with the motor windings. In such cases there may be a solution involving isolating the metal body from PCB ground and allowing it to "float".

Never seen bad motor windings on this model.

Yes, I have seen sluggish/worn bearings which produce a different noise.

But often this causes slow down and hence heads stuck to platter, which is what this sounds like in my experience.

[D_R]

The OP says that "I have a short between the motor supply pins and gnd". Assuming that "gnd" is the metal body of the drive, and assuming this short is at the motor itself, then there is a problem with the motor windings. In such cases there may be a solution involving isolating the metal body from PCB ground and allowing it to "float".

Ok, just to be clear, I removed the PCB from the HDA. On the PCB of the defective Drive I have three pins that are shorted to GND, that are supposed to supply the power to the motor. On the working PCB, I have a resistance of about 470 Ohm to GND. And with GND I mean the Ground Plane of the PCB, on the mounting screws for example.

On the Motor only without the PCB I have a resistance of 7-11 Ohm on one Pad to another. The motor has no GND Connection, it has only the 4 wires going to it. The same measurement I have also on the working drive. So I think that the motor itself should be fine.

[pcimage]

I'm only going by the noise in the recording, which I've heard literally 100's of times before!

[fzabkar]

The patient PCB appears to have shorted low-side MOSFET drivers on each of the 3 phases. There are some diagrams in the following article.

Measuring VCM and Spindle Motor Current:
http://www.hddoracle.com/viewtopic.php?f=59&t=204&p=484
http://www.hddoracle.com/download/file. ... &mode=view

[D_R]

@pcimage
May be you are wrong this time? I opened the drive in the clean room.
https://www.dropbox.com/s/e5elb3qitiz86 ... 1.jpg?dl=0

The heads are in their parking position. But there is a lot of dust on the surface of the top platter. Especially 0.1 x 2-3mm long particles.

@fzabkar
Thank you for the links, I'm going to check them out.

[thatdellguy]

Heads are stuck between the ramp and platter. Resting position is further back on the ramp.

Ignore fzabkar on this one and send it to a proper DR facility if the data is important.

[pcimage]

Ok. Maybe not stuck on the platter, but still stuck.

Nothing to do with PCB.

[fzabkar]

Ok. Maybe not stuck on the platter, but still stuck.

Nothing to do with PCB.

The original PCB tests bad. There should not be a "short" between any phase and ground.

For example, here is the relevant area of a WD PCB:

There are 2.2K resistors (R14/R15/R16) between each of the 3 phases and the common terminal. I measure 2.2Kohm phase-to-common and 4.4Kohm phase-to-phase. This means that the resistance looking into the SMOOTH chip is essentially infinite.

That said, it's odd that all 3 phases test the same. Perhaps there is residual charge on each of the MOSFET gates, causing them to remain switched on after power is removed???

[D_R]

I don't know why I hat the short, but after I put the heads back on to the platters and then again to the ramp, the drive was spinning up and is currently on my imaging machine. But the imaging is very slow.

[labtech]

Next time a simple test is testing the patient PCB (presumbly faulty) on a working donor drive (preamp blocked) - if it spins, then you know what is going on.

[pcimage]

I don't know why I hat the short, but after I put the heads back on to the platters and then again to the ramp, the drive was spinning up and is currently on my imaging machine. But the imaging is very slow.

So, there was nothing wrong with the PCB?

[D_R]

So, there was nothing wrong with the PCB?

No, there was nothing wrong with the PCB. But I don't understand why. The drive span up with both PCBs. And after the imaging process I tested the PCB again and I still had a short to GND of three of four motor supply pins on the PCB.

Well, next time, I'm going to follow the suggestion of labtech and test the "faulty" PCB on the working drive.