First up, not expecting any miracles or such; but thought I'd still see what options could be throw around.

What's been done:
* Already consulted with clean room specialist, based on their experience, and customer's budget, this really wasn't going to be a viable option
* Dedicated linux recovery box with SATA dock combined with ddrescue 1.19, external switching power relay for the drive and a custom script

What's happening:
* Drive will infrequently finally come to life on the linux recovery box, enough such that it gets assigned a device name (/dev/sdc etc) and then ddrescue and get to work.
* In the last 3 days I've managed to get ~60GB of data off, which is about half of what I was hoping to get, but now the drive is being extra reluctant to come back to life.
* Drive will spin up, knock 4 times, pause, and repeat about 4 times before spinning down, and then repeat that whole process about 2 more times before I find I have to power cycle the drive to get the attempt to start all over again.

What I'm wondering:
* Is there a way to work the drive via its serial control port to make it come back up but perhaps with various heads turned off?
* Suggestions?

Again, I realise there's not a lot of hope for this drive and I know power-cycling grind out isn't going to do it much good in its current condition, but this is an EOL situation so it's a case of just seeing what I can get with what's left.

Regards

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You have a backup...right? | Tech Repairs on YouTube

I'm afraid there aren't many things you can do. It looks like one or more of the heads are dead.
Which would mean that the drive needs clean room work. Without that, you're only spinning your wheels turning the drive on and off (and you're causing more damage, as you already know).

I have never used 'free' (or 'pirated') tools like WDR or such and I am not aware if these tools have the ability to disable heads etc, so perhaps someone else can consult on this. If they can, and it's EOL as you said, then perhaps you can pinpoint which heads are dead and image the rest of them. But don't hold your breath about the result.

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SandForce SSD Recovery
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Thanks Northwind, appreciate the comments.

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You have a backup...right? | Tech Repairs on YouTube