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March 2005

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Subject:
From:
"Dehoyos, Ramon" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Dehoyos, Ramon
Date:
Thu, 24 Mar 2005 10:03:17 -0500
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        I would like to see the gauss measurements that start affecting the on-off state of a transistor my self or that assure without a doubt that would not affect them at all. So far I have found not a thing. Even if someone from a company states that are not affected them still does not prove it 100%. How many products claim one thing or another and fail in real life. One way  that I would unscientifically prove it, is to have every type of memory chip, program them, place them in a magnetic field and check their programs again. It may turn out to be an old wives tale that memory chips are not affected by magnetic fields and someone may get burned. In the mean time I would err on the cautious side.
        Regards,
        Ramon
	

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of George Patrick
Sent: Wednesday, March 23, 2005 5:05 PM
To: [log in to unmask]
Subject: Re: [TN] Magnetic Screwdrivers


Ramon:

I'd appreciate that.  It would be a help to see the gauss measurement where
the charges start being affected.  As an "old-timer" tech myself, I distrust
"somebody said" things. I have been burned too many times by
"old-wives-tales" that turned out to have no basis in fact :)

--
George Patrick
Tektronix, Inc.
Central Engineering, PCB Design Group
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
Phone: 503-627-5272         Fax: 503-627-5587
http://www.tektronix.com    http://www.pcb-designer.com

It's my opinion, not Tektronix'



-----Original Message-----
From: Dehoyos, Ramon [mailto:[log in to unmask]]
Sent: Wednesday, March 23, 2005 13:42
To: TechNet E-Mail Forum; Patrick, George H
Subject: RE: [TN] Magnetic Screwdrivers




      All our product uses SS hardware so magnetized screw drivers do not
help, but one of our old timers techs that deals with testing of boards
said: Magnetized screw drivers scramble the programs. So it is not about
erasing the program but altering it. One or many transistors that switches
from high to low will alter the program. It may not happen all the time, but
if it happened one time in a hundred it would be one too many. I tried to
get something in writing about this possibility from big companies that
build EPROMs. Some did not response and one said that the fellow that did
this kind of experiments retired. When ever the right time comes, I will do
some experiments and get back with you.
        Regards,
        Ramon


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of George Patrick
Sent: Wednesday, March 23, 2005 4:24 PM
To: [log in to unmask]
Subject: Re: [TN] Magnetic Screwdrivers


OK.  I have looked at the postings.

I still see nothing that would lead me to believe that a weak magnetic field
could erase an EPROM.  Last time I heard, EPROMS were programmed by
electrical charge (the programming cells are capacitors) and a weak magnetic
field shouldn't induce enough current to change that charge.  I would buy an
High power X-ray erasing them, the current induced by that could be enough
to change the charge and do the job.  I just don't see it happening from the
gauss produced by a magnetized screwdriver tip.

I would still like to see any current references to the contrary if I am
wrong, though :)

--
George Patrick
Tektronix, Inc.
Central Engineering, PCB Design Group
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
Phone: 503-627-5272         Fax: 503-627-5587
http://www.tektronix.com    http://www.pcb-designer.com

It's my opinion, not Tektronix'



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bloomquist, Ken
Sent: Wednesday, March 23, 2005 12:45
To: [log in to unmask]
Subject: Re: [TN] Magnetic Screwdrivers


I would check the TechNet archives. There was a pretty extensive discussion
on this subject a few months ago.

KennyB

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