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G8MNY  > IBM      08.10.21 10:00l 63 Lines 3071 Bytes #999 (0) @ WW
BID : 48915_GB7CIP
Subj: Laptop HDD Repair
Sent: 211008/0755Z @:GB7CIP.#32.GBR.EURO #:48915 [Caterham Surrey GBR]
To  : IBM@WW

By G8MNY                                (New Feb 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

I have an old DEL black & white laptop ideal for /P packet work, as it has the
same 12V socket connections as the TNC & Rig. But over the last few years it
has been more & more difficult to boot up from cold. I say cold as if you leave
it to warmup, or apply a lot of heat (hair dryer) to the drive, you hear a
click & it works 100% with no errors at all.

As this is not a practical solution & compatible replacements are unavailable
(a memory stick & adaptor was my next port of call). Not to be out done &
having a background in real engineering (PRESTEL) on old exchangeable drives, I
decided to strip down the small HDD, to see what was wrong! Opening a sealed
drive not in a clean room, I thought would nearly always result in a damaged
head crashed drive, but I was wrong & have got away with it OK!

Inside the drive you see          - - - - - - - - - - - -
this sort to layout.            /  _-─~~─-_      Park    |
                                 /~        ~\    Magnet
The tiny heads are on the     | /            \  ┌─/      |
end of an pivoted arm which    |        H\    | │*/          H=Heads
also has the head moving     ||           \\   | ││park  |   o=Arm Pivot
bare actuator coil inside     │   Axle()  arm\ │ ││Arm
a powerful magnet.           ||              \ \_││      |
                               |              \ o ===\\
Under the iron oxide          | \  Platters  / \_//    \\|
covered recording platters       \          /   ||coil//
is the brushless platter        \ ~─-.__.-─~       \\ //  |
motor, axle & main bearing.       - - - - - - - - - - - -

As this is a laptop drive head parking (put heads on an inside track for
landing & have less vibration during transport) is important, & this is where
my trouble is.
A steel park arm limiting the head travel, normally sticks the park magnet at
power off. But when cold the actuator coil has not enough force to unstick
this, however when hot this is not quite so powerful, & you can hear a click as
the actuator frees the arm from the magnet. At the end of the arm is a tiny
sliver of something to give a magnetic residue gap to limit the magnet pull.
I now suspect this has worn down a few microns increasing the park magnets
holding power.

This was really an old dodge for sticky relays etc, I applied a sliver of
sticky tape about 2x 3mm to the face the park magnet. This will undoubtedly
wear through in a few 1000 parks but it certainly works! Care was taken not to
"touch" or "breath" on anything in the drive especially the patters, & to
refit the cover as soon as I had finished, each time I looked etc.

I have the old Norton DT (DistTest) utility that runs under DOS, that can
quickly test the whole drive, & also scandisk etc, so far it says no errors, &
it has always booted up from cold OK.

Why Don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP

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