WD Charger WD20SDRW-11VUUS0 power but no spin

[beefstrudel]

I have this Charger USB drive that lights up but doesn't spin with original board. If I flash ROM to an unlocked board it spins up and IDs perfectly. All modules read. Cannot read UA due to encryption however.
Anyone ever had one of these they could fix? Nothing seems shorted out on the board. It doesn't seen to even try to spin the motor up. It only pulls around 140mA.

[fzabkar]

Upload a detailed photo of your PCB.

[beefstrudel]

Hopefully this is good enough. 800067 is the board number

Attachments

[fzabkar]

I think I have identified the supply voltage test points. The preamp area is a bit confusing because I think the latest motor controllers integrate the diode within the IC, so I need to know the voltages at Va, Vb, Vc, Vd.

Attachments

TVS_fuse.jpg (74.4 KiB) Viewed 5856 times

regs1.jpg (64.37 KiB) Viewed 5856 times

bridge_regs.jpg (137.57 KiB) Viewed 5856 times

[beefstrudel]

0.001 volt on Va, Vb, Vc, Vd.
Vx was .556
Vy 2.45

[fzabkar]

And the others?

Can you also measure the other ends of the diodes at Vx and Vy? I may have screwed up the polarities. One voltage should be positive, the other negative.

[beefstrudel]

5V at the fuse, 5V at the TVS diode
V1 4.988
V2 1.812
V3 1.158
V4 .001
V5 1.002
Vx .556, 2.45 on other side
Vy 2.45, 2.34 on other side.

This is all with the ground probe on the USB connector

[fzabkar]

It looks like the bridge is missing its Vio supply. I expect that Vcore and Vio should be 1V and 3.3V. I would confirm the result by measuring the voltage at the capacitors around V4.

The missing voltages at Va,b,c,d and Vx,y could be due to the MCU not turning them on until needed.

[fzabkar]

I think I may be wrong about the bridge supplies.

Pin #14 appears to be the Vio pin. V3 and V4 appear to be Vcore.

Datasheet for JMS578 (similar to JMS579 ?):

https://www.hddoracle.com/download/file.php?id=10552

I would check all the Vxx pins.

More info here:

https://www.hddoracle.com/viewtopic.php?p=24481#p24481

[beefstrudel]

Appears the MCU is dead. Bypassed the USB controller and connected with Sata to PC3000, no status register at all.
Tried swapping MCU to another board, same thing.
I guess its unrecoverable unless anyone knows a way to get around SED v2

[fzabkar]

Is there any chance that the SDRAM could be faulty? Or the MCU crystal?

The MCU and bridge crystals appear to be identical. Maybe you could swap them (if you don't have a scope)?

I'm wondering whether V1 is a boost converter for the spindle servo or VCM. A voltage of 5V on the adjacent capacitors would be expected if the boost is not switched on. Otherwise, I would expect 10V or so.

[fzabkar]

Sorry, I missed this:

Tried swapping MCU to another board, same thing.