I have got a 250GB Western Digital WD2500AAJS-40VWA1. I took it out from an iMac and need to do some data recovery.

The HDD is recognised by windows (and Linux), can access the file system and copy data from it. However it works for only few minutes, after that the HDD gets extremely slow (100 B/s) and the PCB becomes very hot. At that time I start to get I/O errors. I have to wait few hours to cool the PCB to copy for few minutes.

I am using DDrescue to copy data and sometimes it gets stuck. When stuck, the HDD spins up again and again resulting very hot PCB. Sometimes the HDD automatically unmounts itself.

Can anyone help me to identify the problem with the HDD and probable solution?

Thanks in advance

Given your drive model and symptoms, my guess would be that the problem is firmware corruption (which causes the drive to run slow and eventually it may not allow access to data at all). The only solution I know of requires expensive data recovery tools. I don't believe there is any DIY fix for this problem (besides trying to grab very small files quickly before it stops working, if possible).

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It would be not difficult to find out which chip on PCB is running hot. Clean PCB contacts to the motor and multi-pin connector using pencil eraser. If doen't help, consider adding radiator to the overheating chip and 12V fan. If it extend working period, you can hope finishing cloning after few cooling cycles.