EPROM re-use

SuperBee4406

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I have a possible bad EPROM on my Star Trek PCB. Can I just erase the chip and reburn the chip, or should I buy new chips?

Star Trek has 24 EPROMS.

Also can I use the ROM files from mame to burn from, or should I get the files from somewhere else?
 
I find many 'Bad' are just due to image on rom gets corrupted (mostly due to window not having cover). After it gets erased, image burns onto the rom fine and crc read is verified. After erase, if it still shows not being blank, then odds are it is physically bad. I would not just toss a rom away that is bad on a pcb. I will 1st test the rom itself to see if it is just the image that is bad or the rom itself.

Kevin
 
Agreed. Most 'bad' ROMs are simply corrupt. EPROMs work by storing a charge in a gate, and over time these can dissipate (bit rot). Exposure to UV light can also damage the contents of the chip. Rarely are the chips themselves bad - and if they are, you'll find out soon enough as you go to re-use them.

Recently I worked on a Donkey Kong Jr. board. It must have been left exposed to a suitable light source for a while, as all five ROMs on one side of the board were corrupt (no covers on the windows). The chips themselves are fine.

-Ian
 
I've had to replace hundreds of EPROMs / PROMs / Masked ROMs over the years. Early on when I was trying to be frugal and save the EPROMs from an untimely death, I'd say 80 - 90% of the time, the EPROMs were not in condition to be reused. After awhile, I just started replacing them outright to save on time. I still think that bad ones should just be pulled and replaced with fresh parts.

On the other hand, PROMs and masked ROMs - they will need to replaced 100% of the time, no question about it. :) I think masked ROMs were made to fail!

Dave
 
Hehe. Definitely agree with the mask prom bit :) No saving those.

I guess I've just been lucky. I've run across very, very few 'bad' EPROMs that I couldn't salvage. Ocassionally, you'll find some that won't blank all the way - I've had luck programming the whole thing with zeroes, then erasing it again. Sometimes you even have to do it twice. In my opinion, it's worth a shot, and costs nothing to try.

EPROMs that have had mechanical damage, on the other hand, corroded/broken pins, cracked housings, etc - those are just plain bad from the get-go and can't be salvaged. I've had a couple of the old-style ceramic with gold legs type chips where the legs have somehow rotted out, and they just fall off if you so much as touch them wrong. I think it's the same thing happening to them that happens to 70's era TI chips, the underlying metals corrode under the plating.

But, then again, I'm from a hobbyist/hardware hacker perspective, and it's always worth the extra effort to me to salvage whatever I can.

-Ian
 
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