overexposed CMOS EPROM

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.

Does it blank check ok ?

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

Graham

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

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..

they say here to increase it every minute:

Is the programmer reading it right ?

Home built Willem ? I've only ever used commercial programmers and had no problems. Sometimes an Eprom will go 'bad' (rarely). Chuck it.

Not an especially useful site. Try a manufacturer's app note if you can still find one.

Graham

fom the replies - sounds more like you may have a flakey programmer, or you tried to program it with the wrong algorithm and put 21v on a 12.5v programming line.

Greg

Oh yes, that'll kill it nicely. Early 12V Eproms only had the voltage printed on the package rather than a different part number.

Graham

you

nted

but, the thing is, I managed to program two other chips with same setup and they verified OK, and also work fine. the only difference is that those 'good' eproms are 120ns and the bad ones are 150ns. they were all bought second hand, and only god knows how many times rewritten.

all chips can be read with no problem. yes, the willem is home built, but looks pro..

Did the 150ns Eproms EVER work ? Either in the programmer or target system ?

Graham

...and for some, the "A" version was the lower programming voltage part.