Seagate 7200.12 overvoltage damage

[shaun]

Hi there,
just a question regarding the expert's experience with 7200.12 overvoltage damage.
The drive was in an external case and a 19VDC notebook adapter was plugging in.

The 12V suppressor is dead short. I replaced it as I did on dozens of drives sucessfully, it spins up but immediately starts to click repeatedly.
An identical PCB with the SO8 flash swapped (just to make sure) does the same.

Is it likely for this type that I have damaged parts in the closed drive assembly?
Anything worth checking (serial terminal) before sending it off to a DR company if the customer wants to pay?

thanks,
Stefan

[pepe]

Hi Stefan,

Preamp is toasted most probably, which is dangerous, coz it can apply write current uncontrolled, and it leads to destruction of data and servo on surfaces.
So if you are not familiar with cleanroom work i advise to stop things here and if the drive goes to a dr company, warn them about the preamp damage.
It just MUST NOT be powered up in this state.

pepe

[northwind]

Hi Stefan,

Preamp is toasted most probably, which is dangerous, coz it can apply write current uncontrolled, and it leads to destruction of data and servo on surfaces.
So if you are not familiar with cleanroom work i advise to stop things here and if the drive goes to a dr company, warn them about the preamp damage.
It just MUST NOT be powered up in this state.

pepe

+1
exactly so.

[shaun]

Thanks guys, that's what I wanted to hear. Actually, no, but it was what I feared.
Some drives in the past seem to be better protected or less sensitive, when I found a shorted TVS, the drives were mostly fine.
This one isn't. Maybe it's the difference whether the SMPS is plugged into the drive while energized, so with +19 on the output caps vs. being plugged into the drive first and then run into current limiting while starting up against the TVS.

Whatever, I've not worked on HDDs on the clean bench for several years now and don't plan to do it again, so I'll send the customer to one of the DR companies the IT business I worked for usually consults.

[fzabkar]

It seems odd that an overvoltage on the 12V supply could kill the preamp. If the +5V electronics is OK, as it appears to be, and if the -5V supply is within spec, then I'm wondering how the preamp could have been affected.

I would measure the -5V supply. You could also try isolating the spindle motor and communicating with the preamp registers via terminal.

[pepe]

he has replaced the pcb with rom swap, and it clicked, so it is very likely caused by preamp malfunction.

[fzabkar]

I understand that, but I'm still wondering how the fault could be related to the overvoltage.