The only "baking" I've heard about with
EPROMs was *annealing* on the
original prototypes from Intel. I want to say that was before they figured
out UV erasure and were zapping the things with X-rays for erasure. You
won't be doing any EPROM annealing in a home oven :)
It's been my experience that usually defective 2708s or 2716s will fail to
program, rather than fail to erase. Be aware that some of these old EPROMs
take quite a while to erase. Newer stuff like 2764s are usually done in
around 15 minutes with my old UV eraser, but I've had to run old 2708s and
1702s for much longer, 30+ minutes usually. I think my eraser uses a 15W
lamp, for reference.
Try programming all zeros and see if it'll take. If it does, try and erase
them. If you start seeing some bits flip to one but not all of them,
increase exposure time. If you get up around an hour and you still have
zeros in some positions, the EPROM is likely bad. If you're debugging or
developing on something, I wouldn't bother messing around with potentially
bad EPROMs, especially 2716s since those are still pretty available. You
can also drop a 2816 EEPROM in there (there are other pin-compatible
EEPROMs, SEEQ had one, there may be others).
And, of course, be aware that Texas Instruments' 2716 is its own thing and
not compatible with the common 5V-only 2716s. They called their Intel 2716
compatible a 2516.
Thanks,
Jonathan
On Wed, Dec 13, 2017 at 10:33 AM, Michael Zahorik via cctalk <
cctalk at classiccmp.org> wrote:
My homemade 8080 CPM machine used a number of
2708 and 2716 EPROMs. that
was 40 years ago. This machine is still running and I use it, but since I
had trouble with the EPROMs, I switched to EEPROMs. I would also be
interested in hearing about whether or not baking would work and how to do
the baking, exactly. I have a bunch of old EPROMs, that I figured were
dead, but maybe not? Mike Zahorik
From: Holm Tiffe via cctalk <cctalk at classiccmp.org>
To: dwight via cctalk <cctalk at classiccmp.org>
Sent: Wednesday, December 13, 2017 9:17 AM
Subject: Re: EPROM baking
Hmm..I've read about that baking in conjunction with 1702A too..but
don't remember the source of that discussion. I know that ppl suggested
it for proms that would'nt program correctly...
Regards,
Holm
dwight via cctalk wrote:
When I was at Intel, years ago, I recall the
baking was only to repair
the retention of the EPROMs. It was not to fix random
failures.
It sounds like your EPROMs have various failures that wouldn't be
helped by
baking.
Each time the EPROM is programmed, there is a slight increase in the
leakage of
the floating gate. This was typical after thousands of
program/erase cycles. Baking them repaired the damage to the insulating
layer that was damaged.
Dwight
________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of william
degnan
via cctalk <cctalk at classiccmp.org>
Sent: Wednesday, December 13, 2017 6:18:16 AM
To: Mark G Thomas; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: EPROM baking
On Wed, Dec 13, 2017 at 9:08 AM, Mark G Thomas via cctalk <
cctalk at classiccmp.org> wrote:
Hi,
I am working on several projects requiring 2708 and 2716 EPROMs, and
am finding some of my chips will not erase, and some will not take
a program. I've also learned more in the past week than I wanted
to know about repairing Data-I/O 29a/b programmers.
I vaguely remember in the 1990s baking such EPROMs in the oven, but
I do not remember temperature or time. I was surprised that Google
didn't turn up anything useful with this info.
I'm sure someone here will have some notes on EPROM baking.
Mark
Mark,
If this is an issue about reviving bad eproms? I assume you have tried
the
regular stuff.
What process are you using now to erase 2708/16's? I have a simple
eraser
unit and it seems to always work. Some eproms go
bad but I never have
issues with erasing them. My point is that maybe you need a better prom
eraser unit. I would avoid baking them until you have exhausted other
options. Not sure what others think. This topic has come up before
here,
about putting them outside and all that. The
erasers are all over ebay,
and the hardware store is full of the correct types of lighting, why not
make a box that will do the job? I assume there is more to it that
simply erasing them.
Bill
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