hard drive data recovery

From: Christian Fandt <cfandt_at_servtech.com>
Date: Tue Jul 14 09:20:35 1998

At 17:51 13-07-98 -0700, you wrote:
>On Mon, 13 Jul 1998, Tony Duell wrote:
>> What we now need is for some brave person (me, Allison???) to take a
>> number of old (and dead) drives, make a clean box, pull them apart,
>> document everything, and write a repair manual....
>I would love to help with this effort as I'm very good with my hands and
>the whole point of starting this thread was to guage the practicality of
>home hard drive repair, but currently I wouldn't have the time to embark
>on such an endeavor, although at some point I will. I hope that whatever
>tricks I'm able to pioneer with respect to hard drive repair will be
>passed on in FAQs.

Good! We'll be watching, Sam! :-)

>I've already noted the discussions on building a clean box and at some
>point will be creating one. QUESTION: Is there a way to determine just
>how clean such a clean box is after its built? Is there some meter that
>can be hooked-up to the exhaust opening that will give you a particulate

Yes there is a device used to count particles in the air. But you may not
like the cost of them.

My job involves work in our Class 10,000 cleanroom at my place of
employment. A few of you others out there either once had or now work in
such a company that has cleanroom(s), or possibly had spent time in a
cleanroom as a service person.

I can give a brief primer on how a cleanroom is built and short definition
of the federal standard of cleanroom classes if some of you are interested.
That would give a picture of the environment within which the drives had
been manufactured and what one would do to make a simple one for his/her use.

We make linear encoders of which the finest line size of the ronchi ruling
on the encoder substrate is 4 microns (157.48 millionths of an inch.)
Figure one micron = 39.37 millionths of an inch (0.00003937"). Most dust
particles in 'free air' (the air we normally live in and breathe everyday)
are in the 0.5 to 10 micron range. Therefore, keeping the air _clean_
during the manufacturing process has benefited us extremely well. Of
course, semiconductor manufacturers fabricate microprocessors, transistors,
all other IC's in cleanroom environments. Those hokey Intel TV
advertisements with cleanroom workers in full body suits are actually not
far off the mark with regard to the actual need to keep a class 10 or 100
cleanroom clean when making chips with sub-micron features.

I had purchased a particle counter at work to check the "cleanness" of the
air in various zones in the cleanroom. These machines are somewhat
complicated though the basic concept used for counting particles is not.
Most particle counters are sensitive. The one I bought is able to "see",
therefore count, a *single* particle as small as 0.5 micron. Our unit has
similar specifications as other typical brands of particle counters but it
still cost us a little over US$10,000. Used equipment dealers have them for
less but it's still not reasonable for the hobbyist or even a very small
business. Maintenace parts and calibration is also a bit high.

BTW, the air quality in most areas of our cleanroom stays at less than 100
particles per cubic foot. Very clean when considering that outside air
which is relatively clean (say, the proverbial fresh mountain air) has
100,000 to 500,000 particles per cu. foot -more with forest fires, etc.

If I do decide to tinker with some of my dead hard drives, I plan to bring
them to the plant some weekend and have at it :-) I'll just slip on a
boufont (sp.?) cap as a hair cover, special gloves, my lab coat and maybe a
face mask of some sort, setup at an empty table and away I go!

>count? My Panasonic vacuum cleaner has such a detector that triggers a
>dual-color LED on the front panel: it lights red if it detects dirt
>particles passing through the hose and green if the particle count is
>below some threshold.

This is an extremely simplified version of a particle counter. I can
envision it as having a simple LED emitter, probably IR, on one side of the
hose and a photodetector on the opposite side. The detector and the analog
front end may be rather sensitive to differentiate minute changes in light
intensity. When significant amounts of dust and crap are sucked thru the
hose the light is slightly occluded whichs lowers the output of the
photodetector which then trips the circuit driving the red LED on your
Panasonic vac. This is much too coarse of a device to measure air quality
in any home-built glovebox/cleanroom any of us may build. It serves to show
the homeowner that the Panasonic company's wonderful Model Such-and-Such is
doing a great job at cleaning their house. Pure marketing gimmick but kinda
neat on a home vac anyway IMO.

>> Yep, this is an interesting thread for me...
>Me too!

Thanks for starting the discussion Sam, as a few of us who have the
resources will need to get into it in the future -if not now. I can offer
additional ideas and advice from my own cleanroom experience to the group
on setting up a work area using either homemade or used commercial "clean
benches", etc.

Regards, Chris
-- --
Christian Fandt, Electronic/Electrical Historian
Jamestown, NY USA
Member of Antique Wireless Association
        URL: http://www.ggw.org/freenet/a/awa/
Received on Tue Jul 14 1998 - 09:20:35 BST

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