I have a hard drive that I KNOW to be broken (it's a 6.4GB Seagate
from a physically demolished eMachine) but just for the challenge, I
want to see what I can get out of it.  When I plug it in to known-good
power supply, the drive spins up, emits 5 distinct "chirps" and then
spins down.  This is different than anything I've run into before, its
not a BIOS beep code (its hooked up to JUST a power supply) and by the
looks of it (yes, I opened it!), the arm is extending to its limit and
clicking rapidly to make a beep-type sound.  Anyone know if these
beeps are a sort of specific failure code (SMART or otherwise) or is
this an unspecified error?
I don't think I'm going to get anything from this drive, but I'd like
to know for future reference.  Thank you.

Yes your drive was completely knackered even before you opened it up.
When things die, one can at least extract a bit of knowledge by
examining the internals. It?s what I do too. Damned good magnets
inside HDs and the disks make alternative coasters to CDs. Not
absolutely sure if there is a prime fault but causes could be loss of
the FAT, the boot sector, the read circuitry or anything further down
the line. I have fixed a few HDs but the success rate is low and I?ve
never managed to fix a ?click click? failure.

As I mentioned before on another question, my brother (who is not a
techy) lost a hard disk to PSU failure -- a rare relatively
occurrence. He went and bought an identical (cheap) disk on ebay and
swapped the electronics, thereby retrieving all his holiday pictures.
Jammy!

So if the failure was on board you might have been able to salvage
your data, but I more suspect that ?click? failures are surface
faults. Wouldn?t it be really good if FAT and boot sector were
redundantly duplicated by the manufacturers.

Incidentally, the clicking sound is just the mechanism banging off the
end stops because it can?t find the data.

Best

It's a beautiful piece of technology inside, I'll tell you that much.
Thanks for sharing the bit about swapping the electronics... I've yet
to venture that far into hard drive repair/recovery but there's
certainly a lot more to the story than "oh it's just a bad hard drive"
... Now I don't have a cleanroom but it's good to know what's going on
inside.  This seems like an electronics failure rather than a
mechanical failure because it seems to me like the drive was designed
to make this specific sound exactly 5 times and then shutdown but I've
never heard of disks giving off specific audible clues as to their
malfunction.
It looked like the machine was thrown over a fence and beaten with a
bat, plus it was rained on.  Though I didn't have any expectations for
the disk, it powers up just enough to tell me something and I'm
curious as to what that is ; )

:-)

Best