I bought some used 27C256's in a lot on ebay. They had not been blanked. Based on the label and the data on the chip I gather they are pulls from motherboards circa 1990.
All chips I've purchased previously have arrived blank. If I needed to erase and rewrite one of those, 20 mins in my eraser has done it.
I did a bunch of these for 20 mins. I read them in the programmer and it came back all FF. The blank check completes ok. They all error out when trying to write new data. I did a second erase on some of them and same story.
I sent an email to the seller and they said I need to put them in a UV chamber for 24 hours. That sounds like bullshit to me but I thought I would check here first. Is it possible a chip is not erased even if it reads back as blank?
All chips I've purchased previously have arrived blank. If I needed to erase and rewrite one of those, 20 mins in my eraser has done it.
I did a bunch of these for 20 mins. I read them in the programmer and it came back all FF. The blank check completes ok. They all error out when trying to write new data. I did a second erase on some of them and same story.
I sent an email to the seller and they said I need to put them in a UV chamber for 24 hours. That sounds like bullshit to me but I thought I would check here first. Is it possible a chip is not erased even if it reads back as blank?