29 Jan
2009
29 Jan
'09
8:28 a.m.
--- On Thu, 1/29/09, Dave Dunfield <dave09 at dunfield.com> wrote:
From: Dave Dunfield <dave09 at dunfield.com>
Subject: Re: EPROM erase times and lifespan
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Date: Thursday, January 29, 2009, 11:11 AM
Hehe, yeah, I really didn't want to risk ruining any chips, so when I built the
eraser, the timer was top priority. I used the timer out of a junked microwave oven,
replacing the horrible membrane keypad with the numeric keypad sawed off the end of a
damaged Apple IIe platinum keyboard. So mine even has a nice little VFD telling me just
how much time is remaining, a nice little *feep* *feep* *feeeeep* to tell me that it's
done, and best of all, the little VFD flashes "COOK" at the bottom while
it's running :)
Oh, and it doubles as a clock...
But, yeah, I guess I'll try setting the timer
for
longer now, to ensure they're good and blank. I
was always told that too much UV would damage the
chips - I've never left one in for more than say,
15 minutes before. Next time I need to erase
some,
I'll put 'em in for longer than three or five
minutes...
Which is why a timer is a good thing ... I can tell you
from personal experience
that forgetting a tray of EPROMs in an untimed eraser
overnight leads to non-
functional devices. The ones I left in for an hour seemed
to be OK, but I wouldn't
do that on a regular basis - after about the third time I
left the tray in
overnight, I ripped the timer out of a dryer we were
disposing of and made it an
integral part of my eraser. PS: Since you don't know the charactistics of
your
lamp, I'd err on the cautious
side ...
Yeah, hence why I initially experimented with the three and five minutes. That gets most
of 'em 'blank', but I think I'm going to try aroud eight or ten minutes
next time, to get them 'blanker'. Some chips required two doses of three minutes,
others still weren't blank after that. I haven't tried those again yet, but
perhaps I need to do more experimenting.
-Ian