Hi

A friends harddrive that came with his laptop had suddenly become inaccessible.
The drive spins up, the head would run over the platter 2 times every 2 seconds. Not much more than that.

After a while of trying this and that, I suspected the head to be the cause of the problem. I have previously successfully changed headunits on harddrives so this was a piece of cake.
Now with the new head the drive behaves pretty much the same. SO the head exchange was pretty much for nothing. I then changed the PCB. with the new PCB the drive sound more "normal", the heads moves around like if it is reading. in SeaTools it shows up with correct serialnumber of the new board. but it doesnt show the correct size (1TB), instead it shows 0.
when I try to initialize the drive, I get the error "data error cyclic..."

I suppose I have to copy the bios or firmware from the old PCB onto the new...? Can this be done by software or do I have to physically move the chip?

IMO, it is easier to move the chip. If you have a hot air rework station it is a piece of cake. The chinese 858D units are about $70 and will work okay for occasional use. Mine hasn't caught on fire yet.

It won’t be the PCB.

Either the drive has media damage or something’s gone wrong with your head swap. These are to easy to change heads in.

Put the heads back in the donor drive with it’s own PCB and see what happens.

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Yes, then if the donor works okay after putting the heads back in, also try putting the patient PCB on the donor drive (with the donor heads). If the drive starts clicking or making weird mechanical noises, the heads probably aren't compatible.