Question HDD failed. I swapped the PCB but it still doesn't work ?

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MorganDollar

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Dec 5, 2020
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Hi, I have a 2014 WD40EZRX 4TB HDD . One day I connected a Molex cable from my PSU to motherboard. I turned on the PC and I can smell smoke. The motherboard and my WD40EZRX no longer work. I want to retrieve the files inside the hard drive.

Symptoms of the WD40EZRX:
No spin at all when connecting to healthy PC via SATA and via USB docking.

I read on this forum about swapping PCB. I bought 2 same model WD40EZRX hard drives that has the same PCB model (Rev A 2060-77945-001). The dead drive was manufactured in Jan 2014. The 2 new drives I bought were manufactured Jan and June 2014.

I used a multimeter and detected D3 is shorted on the dead hard drive PCB (left most black chip 2nd to the lowest in the image). Image links:

Dead HD PCB board inside
Dead HD PCB Board Outside
Dead HD Label

I swapped the 2 PCB boards to the dead hard drive. The dead drive start to spin. It makes loud clicks. However, both Win 11 and Mac OS said the disk is not readable and suggest initialize. I didn't initialize. I also tried TestDisk on Mac but TestDisk says no hard drive detected. Showing images of one of the replacement drives and the error messages in Mac.

Replacement PCB Board Inside
Replacement PCB Board Outside
Replacement HD Label

Test Disk Mac Shows No HDD
Mac shows HD not readable
Mac Disk Utility Shows 0 Kb

Do I really need to swap the BIOS chip too? What other things should I do?
How likely can I retrieve the data in this drive?
 
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MorganDollar said:
I read this forum about swapping PCB.
Click to expand...
Not all that you can find on forums can be trusted, especially when the topic is either too old or the person talking doesn't know their stuff.

Replacing PCB on HDD is a bad idea.

Why?
That's why:
A common misconception is that a damaged printed circuit board (PCB) may be simply replaced during recovery procedures by an identical PCB from a healthy drive. While this may work in rare circumstances on hard disk drives manufactured before 2003, it will not work on newer drives. Electronics boards of modern drives usually contain drive-specific adaptation data (generally a map of bad sectors and tuning parameters) and other information required to properly access data on the drive. Replacement boards often need this information to effectively recover all of the data. The replacement board may need to be reprogrammed. Some manufacturers (Seagate, for example) store this information on a serial EEPROM chip, which can be removed and transferred to the replacement board.

Each hard disk drive has what is called a system area or service area; this portion of the drive, which is not directly accessible to the end user, usually contains drive's firmware and adaptive data that helps the drive operate within normal parameters. One function of the system area is to log defective sectors within the drive; essentially telling the drive where it can and cannot write data.

The sector lists are also stored on various chips attached to the PCB, and they are unique to each hard disk drive. If the data on the PCB do not match what is stored on the platter, then the drive will not calibrate properly. In most cases the drive heads will click because they are unable to find the data matching what is stored on the PCB.
Click to expand...

What your HDD is missing, for the very least, is the sector map. Sure, it may have a new PCB but without the most crucial part, it is a dead drive. Nor does it have proper firmware (BIOS) either.

If you have valuable data on HDD and want to recover it, bring your HDD to data recovery firm and be prepared to pay a lot more than usual, thanks to your "tinkering".
 
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Aeacus said:
Not all that you can find on forums can be trusted, especially when the topic is either too old or the person talking doesn't know their stuff.

Replacing PCB on HDD is a bad idea.

Why?
That's why:


What your HDD is missing, for the very least, is the sector map. Sure, it may have a new PCB but without the most crucial part, it is a dead drive. Nor does it have proper firmware (BIOS) either.

If you have valuable data on HDD and want to recover it, bring your HDD to data recovery firm and be prepared to pay a lot more than usual, thanks to your "tinkering".
Click to expand...

@Aeacus, the only "sector map" in the ROM would be for defects in the SA, and it is extremely rare to see any. The defect maps and translator for the user area are stored entirely within the SA.

To the OP, measure the resistance of R67 (the zero-ohm resistor near D3). If it is open circuit, then there is a real risk that the preamp on the headstack has been damaged, in which case your DIY adventure is over. In fact, I see a possible burn mark on the motor controller IC (U1). If this chip is damaged, then the preamp would definitely be at risk.

Here is usually what happens as a consequence of these badly designed PCBs:

http://www.hddoracle.com/viewtopic.php?p=5033#p5033

I always recommend the following PCB supplier, as they include a ROM transfer in the price:

http://www.hdd-parts.com/17124424.html
 
Last edited:
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fzabkar said:
@Aeacus, the only "sector map" in the ROM would be for defects in the SA, and it is extremely rare to see any. The defect maps and translator for the user area are stored entirely within the SA.

To the OP, measure the resistance of R67 (the zero-ohm resistor near D3). If it is open circuit, then there is a real risk that the preamp on the headstack has been damaged, in which case your DIY adventure is over. In fact, I see a possible burn mark on the motor controller IC (U1). If this chip is damaged, then the preamp would definitely be at risk.

Here is usually what happens as a consequence of these badly designed PCBs:

http://www.hddoracle.com/viewtopic.php?p=5033#p5033

I always recommend the following PCB supplier as they include a ROM transfer in the price:

http://www.hdd-parts.com/17124424.html
Click to expand...
Hi @fzabkar, I measured the rsistance of R67. It is 66.1 ohms. So hopefully this is a good news?

​

 
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Hi @fzabkar, I retested. Here are the results:
PCB Board from failed hard drive: R67 is about 66 ohms. R64 is 0.01 ohms.
PCB Board from working hard drive: Both R67 and R64 is 0.01 ohms.

If 66 ohms high enough to be open circuit here?
Is there any chance I can retrieve the data by swaping the PCB board with BIOS chip transferred?
 
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Did you remove D3? If not, then I think you are seeing the resistance of the rest of the circuit, not the resistance of the zero-ohm resistor.

What is the resistance between SATA +5V and ground (any screwhole)? Do this with the PCB on and off the drive. In this way you will be measuring the preamp as well. You can compare these measurements against your donor.

What is the resistance of D3?
 
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Hi @fzabkar,

All readings are SATA 5v pin to screwhole on PCB.

PCB from failed drive readings:
Failed PCB alone without hard drive: 67.2 ohms.
Failed PCB attached to failed hard drive: 36.1 ohms.
Failed PCB D3: 0.08 ohms -- this is why I said it is shorted

PCB from working drive readings
Working PCB alone without hard drive: Very high 150k+ ohms.
Working PCB attached to working hard drive: Very high 150k+ ohms.
Working PCB attached to failed hard drive: 71.6 ohms.
Working PCB D3: Very high 150k+ ohms.

Do these tell you anything?
 
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That cable connects to the spindle motor. The preamp is connected to the 20-pin connector (J1 on the PCB). The burnt cable in my linked photo is inside the HDD.

Donor Drives is the only other company that I'm aware of that offers a firmware transfer service. However, I don't recommend them. They are more expensive, anyway.
 
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