15 Jul
1998
15 Jul
'98
6:06 a.m.
At 09:50 15-07-98 -0400, you wrote:
< Alright for some :-). Alas most of us don't have access to a clean room.
< Even if I was working at a place which had one, I can't believe they'd be
< too happy if I wandered in with an HDA and started stripping it.
Majorly true.
I worked in pharmaceuticals and though they didn't use super clean rooms
(class 10,000 worst case) the equipment was under a laminar airflow curtain
with a flow of 100 linear feet per minute and the air under there was class
100. The air flow was obvious ly of the the machine then into the room
where super clean was less important.
This is the case in our cleanroom. I do in fact already work on stuff that
has to be kept clean by taking it into the cleanroom. I work on it in a
room area that is not in the 'critical' clean region of the group of rooms
consisting of the whole cleanroom. Our cleanroom is built to class 10,000
but as Allison states, because of the laminar flow (figure an air flow
pattern kept strictly parallel to the direction it is traveling, no
turbulence) the cleanest areas in those critical areas are under that air
curtain.
If I took a 5.25" DEC drive in there to work on, it would be at a desk in
front of a Balzers vacuum coating system which uses four LSI-11/23
(KDJ11-AA) processors for controlling various parts of itself (we do NOT
load substrate for coating through the front door, we only clean and
maintain the unit there, therefore it is one of the "dirtiest" areas of the
cleanroom). The drive would feel it is amongst friends <g>.
< I would have thought looking for backscattered light would be more
< sensitive and easier to set up. Still not sensitive enough for a clean
< box, of course (in this form).
The air flow and the sensing area cross section are important. Using a
light source like a laser is helpful in getting the backscatter brighter.
This is the problem of how many Angeles can dance on the end of a pin.
You build a clean box and use a good HEPA filter. With 100-200cfm of
incomming clean air once the dust in the box has been blown out it will be
clean especially if gloved hands are the only thing inside.
I'e heard a lot of "good luck", "it will not last" and "too
dirty" from
those that haven't. I've done it, when RD53s and 54s were in desperately
short supply here and it does work without the clean box with some care.
Obvious tricks like wearing nylon gloves to avoid finger prints, a canister
of dry air to blow things off and keeping the unit covered when possible
all reduce risk.
Allison
I feel that when precautions and care are taken such as what Allison states
above, one would have a quite functional cleanbox workstation. He/she could
be fairly confident that intrusion of the platter area of a drive would
yield a successful repair -if the source of a problem is indeed found(!).
--Chris
-- --
Christian Fandt, Electronic/Electrical Historian
Jamestown, NY USA
Member of Antique Wireless Association
URL: http://www.ggw.org/freenet/a/awa/