>         Got a HDD that stopped working.  I'd like to get some data off it, but
> want to try and do it myself (it's that tinkering thing).  It spins up.  I
> do NOT hear the normal scratchy noise like when the heads crash.

Well, thats a promising start.

>         Tried putting it in the fridge for 30 min. and then running it (had a
> couple people say this might work).  No luck.
>         Tried tapping it on all sides.  No luck.

Tapping is for when the heads stick to the drive platter.

>         So, I bought another drive exactly like it.  First I tried swapping the
                                     ^^^^^^^^^^^^^^^
INCLUDING the revision level of the electronics??

> electronic board from the good HDD to the bad HDD.  No luck.

A good start but the HD preamps or servo amp may have been toast. A write
amp failure would wipe out the servo sectors and render the platter unreadable.

>         So, I started to get desperate.  I too apart the drives and took the head
> units out and swapped them.  No luck.  At this point I have swapped

You'd have to get the 'home' position -exactly- correct for the drive
to initialize properly. Did it try to move the heads across the platter?
Did it bang them at one end, several times trying to find home track?

> EVERYTHING from the good drive to the bad drive except the platters and
> motor that makes them spin and still have had no luck.  The PC just doesn't

Did they bad platters spin at the correct rate? If one field (or FET) of the
drive motor was out, it shouldn't spin, but if it did, it would
be slow and so the data would not decode properly.

> see the HDD there at all.  I can put a good HDD in there and it works fine

Even with the NEW electronics? Generally a drive will respond to
a 'drive identify' command even if there are problems with the media.
What make/model of drive are you trying to resurrect?

> (so it's not the PC itself).

A reasonable presumption, assuming that when you moved the heads over,
you also moved the matching electronics. Even then, they have
changed the way they write the tracks and so the firmware
won't recognize the old platter format (hence the importance of matching
the revision levels).

>         I moved everything back to the good HDD and it still works.  I know the

Wow. You can fix my dead drives anytime. I did the same as you, but the
Seagate guts simply refused to recognize the platters after the move back.
(the 1.6GB drive were notorious for failure).

> whole deal about "clean room environment", but hey it still works for now.

As long as you keep the big sticky stuff off the media, you can do ok
with a final blast of canned air to clean it off.

>         Anyway, does anyone have a clue what to try?  Since I swapped everything,
> I can't figure out what's wrong.  Is there something you have to do to make
> the new head unit recognize a new set of platters?

I think your problem may be a difference in the media formatting between
the old and the new. Did you try using the New heads with the OLD
electronics in case it was a preamp problem (Connor drives were bad
for servo amp failure).

Do you have a scope that you could use to compare the head signals
between the two drives? If a head controller failed, it could wipe
out the servo sectors with the results that you describe above (new
everything but still no joy). It could also be that you didn't quite
get the home position correct so try again with new heads/old electronics
IF you see that sll heads product correct looking signals. You'll need
at least a 50Mhz BW scope to see the RF envelopes correctly.

Robert

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