Path: utzoo!mnetor!uunet!husc6!cmcl2!phri!cooper!gene
From: gene@cooper.cooper.EDU (Gene (the Spook) )
Newsgroups: sci.electronics
Subject: Re: build-it-yourself EPROM erasers
Message-ID: <1207@cooper.cooper.EDU>
Date: 20 Feb 88 03:30:24 GMT
References: <1714@aurora.UUCP>
Organization: The Cooper Union (NY, NY)
Lines: 47

in article <1714@aurora.UUCP>, jbm@aurora.UUCP (Jeffrey Mulligan) says:
> 
> From article <21651@clyde.ATT.COM>, by gwu@clyde.ATT.COM (George Wu):
>> 
>>      A shown in an earlier post, a pretty inexpensive and cheap UV eraser
>> can be built. But why not use a huge piece of expensive equipment;
> 
> 
> I am surprised that noone has mentioned just setting the little devils
> outside in full sunlight for a couple of hours.  This is obviously feasable
> only in certain parts of the country and when tight schedules do not
> have to be maintained, but would seem to be the cheapest solution.

Erasure by sunlight can take up to a week or two in most places. Unless
you have a short UV filter to cover up the window, you'll also throw
every other wavelength the sun has to offer at the poor little bugger.
I doubt that it could kill the chip, but why take chances?

You erase EPROMs with short UV (ie: less than 2500 A). Fluorescent bulbs
etc. emit longer UV (about 4000 A), which can erase the chip *over* *time*.
That means your computer's BIOS could eventually be erased by casual
exposure to fluorescent lighting (usually at the worst possible time!),
but it is inefficient at best to try to erase an EPROM using this method.

I made an el Cheapo UV box with a $20 bacteriological (sterilizing) lamp
and a small matching fixture. Mounted in a (rather cumbersome) box with
conductive foam on the bottom, the lamp does just as much as the store-
bought variety eraser. Total cost was about $40. Now, I see much more
compact and useful erasers for ~$60, sometimes less. If I had to do it
all over, I'd probably just buy the cheapest UV eraser on the market.
After all, they *do* get the job done, even without fancy bells and
whistles. Have fun!


					Spookfully yours,
					Gene

					...!ihnp4!philabs!phri!cooper!gene


	"If you think I'll sit around as the world goes by,
	 You're thinkin' like a fool 'cause it's case of do or die.
	 Out there is a fortune waitin' to be had.
	 You think I'll let it go? You're mad!
	 You got another thing comin'!"

			- Robert John Aurthur Halford