Hi,

Im new on both this forum as well as on the topic. Since my Hitachi HDD stopped working some time ago i've been looking for a PCB to make it work again. Due to a defective external case the disk stopped working (didnt make any noise or movement, not detected by bios). Fortunately i found a working drive, same model, MLC and same code (first two lines) on the sticker on the pcb and same code on the chip (details given below).

However, my defective hdd wont work with this new pcb. When i place the pcb of the defective hdd on the new, working drive it actually does spin and work (able to transfer data). Does this mean that the problem does not lie with the pcb or could it be possible that my defective drive needs his own bios chip from the original PCB? This might sound silly since the other drive can work with both pcb's. However, the problem was caused by a power failure so my guess (hope?) is that the PCB would be defective, not the drive itself.

Could it be that 1 hitachi drive can boot with 2 different pcb's while another drive needs its own bios? Any help is more then welcome

Hitachi deskstar
Model: HDS722525VLAT80
P/N: 14r9249
MLC: BA1254
2 LINES ON THE STICKER: OA29245 (and) ba1327_
code on the infineon chip: OA29003

NB. Al these match on the 2 different drives

Many thanks in advanced!

From the info given:

1. It's very rare for two Hitachi drives to be able to work off the same PCB, so you are very "lucky" to find two PCB's with NVRAM containing the same SA starting address.

2. If your "bad" drive doesn't spin with either PCB, and the "good" drive spins and works with both PCB, then chances are your preamp is blown. This is rare without the PCB failing too, but not unheard of.

If that's the case, then it's the end of the road for DIY

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Thnx for the help!

Is there any way to make sure its the preamp and/or exclude any other possibility?

I would stick a business card between the HDA contacts of the new PCB and new drive. If the drive still spins up, then this will prove that the PCB doesn't need to see a preamp in order to spin up. If this turns out to be the case, then I would perform the same test with the old PCB on the old drive. If it spins up with the business card in place, then this would suggest that the preamp may be shorting the negative supply.

Another test would involve measuring the resistance between ground and the negative supply when the PCB is on the HDA.

Is this your board?

http://www.hdd-donor.com/pics/1343216345.jpg

If so, then measure the voltages at the 100uH coils (L1 and L3) with the board off the drive. One will have a negative voltage (eg -3V, -5V). This will be the negative supply for the preamp. Now power off the PCB, reinstall it on the drive, and then measure the resistance between ground and the same test point. If the resistance is low, then the preamp will be shorted.

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