Strange issue with 27C512

[KenshinPT]

Hey guys!

I know that parallel EPROMs are not the latest hi-tech technology but I have a problem to solve.

I have two equipments which have a 27C512 EPROM. One of them is faulty the other is OK. I found that the problem is the memory.

So, as to replace the memory, I read the dump from the good EPROM using a Genius G540 programmer. The dump was read OK (I guess).

Them, as far as I know, I used a new and blank 27C512 also from the same manufacturer (ST) to program it.

However, the programming failed. I just got a 73h on the 1st position, and the rest full of FFh. The strange is that the 1st position of the original dump is not even a 73h!!!! ^^!

Then, as I don't have (yet) a UV eraser, I tried to erase on the sun... yes I know it could take a couple days/weeks depending on the sun.

But the must strange thing is that after a few hours of sun... I got "zeros" where I had "ones". How can that even be possible? The UVC only changes "zeros" to "ones"... not the vice-versa :/

Do you think that the new EPROM is faulty? When I bought it it was supposed to be new and blank!

Thanks!

[vuno01]

bro use a bank note checker
and erase them in about one hour or so
and they extremely cheap aswell

[BigJ]

Sometimes when I program a ST 27c512, I get verification errors, so I just click on the program button a few times (2 or 3 times) over until it verify ok. But this only happens with ST chips. Never have any issues if I use AMD chips though.

[KenshinPT]

bro use a bank note checker
and erase them in about one hour or so
and they extremely cheap aswell

Are you sure a bank note checker work? Did you already use that method?

I am saying that because I think those note checkers use a black light and black lights won't erase EPROM...

Well, like a regular fluorescent bulb, they can do it but it can take like a year or so.



Sometimes when I program a ST 27c512, I get verification errors, so I just click on the program button a few times (2 or 3 times) over until it verify ok. But this only happens with ST chips. Never have any issues if I use AMD chips though.

Thanks for the tip!

Which programmer do you use? Genius G540?

I tried to do what you said above, but after the write I can't write anymore bit into the EPROM unless I erase it with UVC rays!

Well... there is a trick to write non blank EPROMs, but you can only write "zeros"! If you have a "one" that you need to change to "zero" you can only do that with UVC radiation.

Thanks though!

[paro44]

Maybe you get some new ideas from this thread: http://www.digital-kaos.co.uk/forums/f152/eeprom-fm27c512-errase-252006/

[KenshinPT]

Just to keep you guys posted! I tested with the bank note checker for 10 minutes, 20 minutes, 1 hour, 2 hours, 4 hours and 8 hours.

No success on erasing it!

Today I am gonna use a UVC lamp to check if the problem is the EPROM, or not!