I have to disagree. I've been reading a lot of your post, I was almost sure I could fix that PCB myself as your post have been very helpful and I can fix standard PCB pull-up resistor, diode issue.
That one is different. SSHD with NAND are not common and I never had one before, so instead of doing something that I would regret I prefer asking. I've learned something, next time, I'll look for DC-DC converter.

I use R&D Lab PSU everyday to troubleshoot smartphone.

I'm watching a thread in another professional forum where someone, who is equipped with PC3K and Atola forensic tools, is asking where to find the ROM on a WD PCB (U12), and whether this ROM needs to be transferred to the donor. So tools are one thing, but knowing what to do with them is another. Assuming there is no NAND fault, I could troubleshoot and repair your drive with a $5 multimeter, a short length of wire, and a soldering iron. And it's not because I have any special insight, I'm just applying basic principles.

In your case there is no logical flow in your approach. Any chip level technician who has worked on microcontroller based devices understands that there are 3 primary things to check -- the power supplies, oscillator and reset pin. You don't start by examining the tiny capacitors and resistors (BTW, those tiny black components are usually resistors). These days most electronic devices, including smartphones, HDDs, motherboards and TVs, have switchmode step-down DC-DC converters. The 3 landmarks which identify these power supplies are a piece of silicon, an inductor and one or more capacitors. The silicon component sends pulses into the inductor, and the capacitor smooths these pulses to produce a flat DC output. The output voltage appears at the junction of the inductor and capacitor(s). Look for the inductors and you've found the supplies. It's as simple as that.



http://www.hddoracle.com/viewtopic.php?f=59&t=231

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A backup a day keeps DR away.

I'll look for that next time before posting.

Injecting 3,3 V didn't help, still BSY and no terminal. I am looking for a donor PCB, yet haven't found one.

This? https://docs.google.com/presentation/d/ ... 3_143_1135

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Joep
http://www.disktuna.com - video & photo repair & recovery service

Just to check, you have removed the inductor and injected on the right hand side pad?

Did you measure the resistance to ground of the line before doing that, what was the value? this will show if the nand itself shorted to ground. Is anything on the pcb or the nand getting hot and what was the draw on the 3.3v you injected?

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Line to ground = 210 Ohm.

When connected (PCB on HDD), PCB takes 0.045 from PSU.

Yes, that's it. It starts off like a kindergarten lesson, but it eventually picks up. It seems to me that Rossman didn't do much formal training on the subject, but picked it up mostly on the job.

When you get past the basics, this excellent site has a comprehensive rundown of electronics concepts, including animations.
http://www.learnabout-electronics.org/index.php

Buck converters are the most common DC-DC converters you'll see in HDDs and SSDs.

Buck Converter Operation:
http://www.learnabout-electronics.org/PSU/psu31.php

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A backup a day keeps DR away.

I'm about out of ideas other than just blindly blaming the nand. I might bridge the 3.3 back to the other pad in case it's needed anywhere else but I doubt it. Needs the experience of a Senior member of Ace support I think, I be wary of just swapping PCB's

_________________
Data Recovery Services in the UK.
https://www.usbrecovery.co.uk/

Would it worth using the ROM from an ST500LT032 to test the PCB? If the PCB then spins up the drive, we can be reasonably confident that the problem is with the NAND or ASIC. I'm assuming that both models have the same MCU and motor controller, otherwise this won't be a conclusive test.

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A backup a day keeps DR away.

I've found a cheap donor, I'll get it before end of the week, I'll keep you posted.

Drive works with donor. I'll compare voltage later.

You might like to measure the voltages on the tiny bypass capacitors surrounding the ASIC chip. To me it's not clear whether this chip needs a Vcore supply, or whether it runs solely off +3.3V.

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A backup a day keeps DR away.