Re: overexposed CMOS EPROM

On Aug 2, 6:02 pm, Eeyore <rabbitsfriendsandrelati...@xxxxxxxxxxx>
wrote:
orange wrote:
On Aug 2, 5:10 pm, Eeyore <rabbitsfriendsandrelati...@xxxxxxxxxxx>
wrote:
orange wrote:
well I've done it, I apparently overexposed the EPROM (27c400) by UV
lamp. (now I know there is such thing)

How long did you give it ?

Graham

I think about 4(min) (the scale is not labeled it goes from 1 to 10).
but I have exposed it twice in succession. the window was dirty and I
wasn't aware of the danger.

8 mins isn't going to break it by miles. I bet it's barely erased it.

Does it blank check ok ?

well that is the problem, its ALWAYS blank, full of FFFFFF..
it doesn't even start programming..

BTW, I've got another EPROM that programs ok, but fails to verify.
strange thing is that when I read it and save it to file, that file is
the same as original, no errors. But willem still fails to verify it..



I used 30 mins as a typical erasure time. If in doubt an hour won't hurt.

they say here to increase it every minute:
http://wiki.xtronics.com/index.php/How_EPROMS_Work#Erasing_an_EPROM



Graham

p.s. if you can find a suitable programmer (see ebay) flash is SO much
better.

.

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