I have a desktop hard disk of we 500gb internal. One day, I started my pc, it was showing to select a boot drive, no hard disk was detected. And also no spinning sound or vibration is comming from it.
I have already checked the TV's diodes, no burnt on circuit board of hdd.
Please help me. I don't want to lose my data.

Isolate the 20-pin connector, leave the motor contacts. If the engine starts. The switchboard or heads died. If it doesn't start, change the board.

How to isolate 20 pin connector

Tape or thin card like a business card.

... and whilst you're at it give the connectors a clean off and check the 0 ohm resistors around power in.

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I have done this already...all things are working and fine....but don't know what's the problem

Is there any way to check voltages using multimeter...on what points should I check voltages on pcb

I'm curious to know why you're asking where to check if all things are working and fine.

You can start with continuity on the diode D1 & D2 and then look at L1 & L2 any caps shorted to ground. What's the drive model number and PCB number. I don't think members mind helping but we can't do it for you.

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

if the motor is spinning with isolation of switch heads. so the problem is in the hermoblock, you need to change the heads.

I already mentioned that the motor is not spinning even after isolation of 20 pins
Model no. is wd5000aakx.
PCB board is 2060-771640-003 rev A.

Replace the entire PCB with Identical one and transfer U12 from patient to donor.

I want to repair this one....please try to solve this

Measure the 3 voltages (V1, V2, Vneg).

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A backup a day keeps DR away.

From a working PCB for info.

V1 : 1.10
V2 : 2.57
V- : 0.08

In terms I can understand - that is to say very simple is there a reason to measure the values on the caps and not the inductors themselves, other than ease of access ?

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Data Recovery Services in the UK.
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V- is probably 0 because the firmware switches off this supply if it doesn't detect a preamp.

I use the inductor as a test point just because I cannot always tell which capacitor is connected to it. In general I would use the least "busy" test point to minimise the risk of damage if the probe were to slip off.

_________________
A backup a day keeps DR away.

I got these values

What are the output voltage at these points?
I am getting 0V, 0.14v at all 4 pins

Also, it is showing zero continuity value from ground to these 4 pins.

I was just about to ask you to check there you should be getting around 6v. track the voltage back to the motor controller there looks like liquid damage to the pcb in that area.

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

No there is no liquid damage.

This level of corrosion is not normal. That should be a nice clean copper ground pad.

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