First I thought this could be a classical one: After a power surge, a chip on the PCB on my Maxtor Diamondmax Plus 9 200 GB burned out (the little one on the left labeled "SMOOTH") and the HDD didn't spin anymore. Following the experiences here and elsewhere, switching the PCB with an identical one could help. So I did - and it burned, too. This time it was the little IC on the upper left corner of the board. Now, I looked for professional help and contacted Ontrack Recovery. After a week of diagnosis, the result was a knockdown: Because of severe damage to the hardware including the read head, all attempts were unsuccessful.
Meanwhile, I obtained another suitable PCB and tried it out (there was nothing to lose). The disc began to spin but wasn't recognized. After a while, a clicking noise (presumable the reading head hitting the edge/case) set in - but no circuit burning.
Now, I'm regaining hope: Is there anything else worth to try out? Could another PCB work? Has the ROM to be switched? Or is a read head damage still possible?

Addition: It's not exactly a clicking noise, more some sort of scratching/"searching" noise (but it doesn't sound like a headcrash or something else doing damage). It starts about 15 second after power-up, it is permanent and nearly regular (sometimes two of these noises follow up each other very fast).

Sometimes when u get a PCB burned, some times the shortcut damaged the MHA

If u get a one click could be SA but if u heard countinusly click could be a Bad Head or preamplifier

Sounds like preamp to me, this often causes PCB burn

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Preamp chip on the MHA got burnt initially(it was shorting inside and burning your donor board).
In Ontrack they probably replaced the MHA or just the preamp but it didn't work and they didn't even bother to put their donor MHA back into donor.

So anything I (or somebody) can do?