Seeking Opinon on EPROM Problems

e. These are Karaoke machines which are modified CD/DVD players.

rth that was even weirder but that was only one out of a bunch. Also, out o f a bag of EPROMs they have the same symptoms. We got alot of parts that ar e used and that is something totally else to deal with.

these EPROMs around (I spent the better part of a day switching them...

Well, if the EPROMs were really in a bag... that usually isn't proper stor age. Read and generate checksums for the EPROMs; if the checksum is wrong, diffe rent from others with the same version label, that's a bad part. I wouldn't waste time erasing/reburning old parts (are they UV EPROMs, or f lash, or EEPROM?), I'd just program a flash replacement. The parts are cheap enough, and 'the better part of a day' is not.

Of course, generate a checksum after burning, verify that before using the part.

One symptom that EPROMS can exhibit is speed related. You can test them all day in an EPROM programmer, but they still won't work in the product. This was a problem in some early Compaq 386 laptops. And some TEK instruments. Reading the device in the programmer, then writing it back fixed 'em. The laptop ones failed again eventually. As I recall, the designers let some of the control lines on the prom float. I guess that allowed some electrons thru to contaminate the bits. New chips soon exhibited the same symptom.

e. These are Karaoke machines which are modified CD/DVD players.

rth that was even weirder but that was only one out of a bunch. Also, out o f a bag of EPROMs they have the same symptoms. We got alot of parts that ar e used and that is something totally else to deal with.

these EPROMs around (I spent the better part of a day switching them to nu merous mainboards)Would you think the EPROMs went defective or they got hit with a software error, like having the plug pulled at the wrong time ? The se things DO have mechanical power switches.

h of them really cheap and they ARE the problem.

ng costs money. But if I order a shitload of ICs and the same thing happens that is worse.

be software I need zero parts. Just put in a chip with a the good data and bam it is done. How long it lasts depends on alot of things, cosmic rays n shit. (I shit you not, there are articles on that, in fact should I put a f oil tape on top ?)

? Note that we also got rush jobs. Not really rush but they have been ther e long enough.

Most of what I see are the 25 series eeproms that Chinese and Black Friday TVs come with and they do corrupt. They also will sometimes suffer eeprom hard failures.

Many times, I can pull the eeprom and copy it (assigning it a file name tha t denotes it's questionable status) and write it right back restoring norma l function. When this works, I change the file name to indicate it's a goo d .bin file.

Other times, I can copy the file but need to program a new blank for it to work.

Most of the times though, I can't get a good file from the old eeprom (simp ly corrupted) and need a good file. Of course, manufacturers won't supply the .bin file but any TV I get in for repair gets it's eeprom pulled and co pied regardless of what it's in for. If I'm forced to buy an eeprom or a m ain board I pull that eeprom and copy the file to my computer so I won't ha ve to buy another one.

Eeproms are cheap. Typically you can get 10 of any given number for less t han $10 including postage from China.

I am not familiar with the machines you are repairing, but I might be able to help you have your questions better understood.

EPROMs are erasable programmable read only memory. They are erased by shining UV light in that little window. The cover keeps stray UV light out - NOT "cosmic rays and shit". One thing to keep in mind is you MUST erase them before reprogramming them. Later parts were EEPROMS. EE stands for Electrically Erasable. Those don't have the little windows. You don't Flash PROMS, EPROMS, or EEPROMS. You program them.

Modern technology uses none of the above. Instead, a completely different technology called flash is used. So, when you flash something, you are updating the flash memory in the device - not an EPROM.

Best of luck with your repairs.

I misspoke, they are EEPROMs.

I would say mistype but that implies a typo, which it is not, I called them the wrong name.

Bottom line is I think you all got me talked into getting new EEPROMs for these things.

The 27 series EPROMs are about $1 each from Chinese vendors on eBay. These are used, erased and "tested". New ones in small quantities (yes, they are still made) are around $40 each.

In my case, the $1 ones are worth the gamble, but I am not getting paid for my time and effort, and if they fail, I can just pop one out and put in a new one.

If I were getting paid for my time, or selling a product, you can be sure I would buy new ones.

Geoff.

Electrical drop-in replacements in flash are not unavailable; 5V, 128k x 8bit Flash is under a buck a chip at DigiKey, in PLCC packages that can be mounted in a socket on an adapter to your (probably) DIP-style sockets.

If there's many sizes, though, it could be awkward to adapt to some of the old parts sockets. It looks like the 32-pin DIP is still available, in 1M, 2M, 4M bit sizes. "SST39SF040-70-4C-PHE" is the 4M version.