Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old January 8th 16, 06:32 AM posted to sci.electronics.repair
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I have a bunch of the same units now that I kinda work for factory service. These are Karaoke machines which are modified CD/DVD players.

I get like three different symptoms on certain models. OK there was a fourth that was even weirder but that was only one out of a bunch. Also, out of a bag of EPROMs they have the same symptoms. We got alot of parts that are used and that is something totally else to deal with.

Anyway, when you find there are only three major symptom sets that follow these EPROMs around (I spent the better part of a day switching them to numerous 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 ? These things DO have mechanical power switches.

But then this is a Chinese manufacturer and they might have gotten a batch of them really cheap and they ARE the problem.

To exacerbate this dilemma, these things are shipped in worldwide. Shipping costs money. But if I order a ****load of ICs and the same thing happens that is worse.

If it is a software thing, I got the EPROM copier and if it is likely to 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 ****. (I **** you not, there are articles on that, in fact should I put a foil tape on top ?)

And what if I get cheap EPROMs and they go bad ?

Well, that's the question. Start flashing the chips I got or get new ones ? Note that we also got rush jobs. Not really rush but they have been there long enough.

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Old January 8th 16, 08:26 AM posted to sci.electronics.repair
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On Thursday, January 7, 2016 at 9:32:43 PM UTC-8, wrote:
I have a bunch of the same units now that I kinda work for factory service. These are Karaoke machines which are modified CD/DVD players.

I get like three different symptoms on certain models. OK there was a fourth that was even weirder but that was only one out of a bunch. Also, out of a bag of EPROMs they have the same symptoms. We got alot of parts that are used and that is something totally else to deal with.

Anyway, when you find there are only three major symptom sets that follow 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 storage.
Read and generate checksums for the EPROMs; if the checksum is wrong, different 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 flash, 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.
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Old January 8th 16, 11:51 AM posted to sci.electronics.repair
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Default Seeking Opinon on EPROM Problems

On 1/7/2016 9:32 PM, wrote:
I have a bunch of the same units now that I kinda work for factory service. These are Karaoke machines which are modified CD/DVD players.

I get like three different symptoms on certain models. OK there was a fourth that was even weirder but that was only one out of a bunch. Also, out of a bag of EPROMs they have the same symptoms. We got alot of parts that are used and that is something totally else to deal with.

Anyway, when you find there are only three major symptom sets that follow these EPROMs around (I spent the better part of a day switching them to numerous 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 ? These things DO have mechanical power switches.

But then this is a Chinese manufacturer and they might have gotten a batch of them really cheap and they ARE the problem.

To exacerbate this dilemma, these things are shipped in worldwide. Shipping costs money. But if I order a ****load of ICs and the same thing happens that is worse.

If it is a software thing, I got the EPROM copier and if it is likely to 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 ****. (I **** you not, there are articles on that, in fact should I put a foil tape on top ?)

And what if I get cheap EPROMs and they go bad ?

Well, that's the question. Start flashing the chips I got or get new ones ? Note that we also got rush jobs. Not really rush but they have been there long enough.

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.
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Old January 8th 16, 01:26 PM posted to sci.electronics.repair
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Default Seeking Opinon on EPROM Problems

On Friday, January 8, 2016 at 12:32:43 AM UTC-5, wrote:
I have a bunch of the same units now that I kinda work for factory service. These are Karaoke machines which are modified CD/DVD players.

I get like three different symptoms on certain models. OK there was a fourth that was even weirder but that was only one out of a bunch. Also, out of a bag of EPROMs they have the same symptoms. We got alot of parts that are used and that is something totally else to deal with.

Anyway, when you find there are only three major symptom sets that follow these EPROMs around (I spent the better part of a day switching them to numerous 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 ? These things DO have mechanical power switches.

But then this is a Chinese manufacturer and they might have gotten a batch of them really cheap and they ARE the problem.

To exacerbate this dilemma, these things are shipped in worldwide. Shipping costs money. But if I order a ****load of ICs and the same thing happens that is worse.

If it is a software thing, I got the EPROM copier and if it is likely to 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 ****. (I **** you not, there are articles on that, in fact should I put a foil tape on top ?)

And what if I get cheap EPROMs and they go bad ?

Well, that's the question. Start flashing the chips I got or get new ones ? Note that we also got rush jobs. Not really rush but they have been there 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 that denotes it's questionable status) and write it right back restoring normal function. When this works, I change the file name to indicate it's a good .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 (simply 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 copied regardless of what it's in for. If I'm forced to buy an eeprom or a main board I pull that eeprom and copy the file to my computer so I won't have to buy another one.

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

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Old January 8th 16, 04:06 PM posted to sci.electronics.repair
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On Friday, January 8, 2016 at 12:32:43 AM UTC-5, wrote:
I have a bunch of the same units now that I kinda work for factory service. These are Karaoke machines which are modified CD/DVD players.

I get like three different symptoms on certain models. OK there was a fourth that was even weirder but that was only one out of a bunch. Also, out of a bag of EPROMs they have the same symptoms. We got alot of parts that are used and that is something totally else to deal with.

Anyway, when you find there are only three major symptom sets that follow these EPROMs around (I spent the better part of a day switching them to numerous 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 ? These things DO have mechanical power switches.

But then this is a Chinese manufacturer and they might have gotten a batch of them really cheap and they ARE the problem.

To exacerbate this dilemma, these things are shipped in worldwide. Shipping costs money. But if I order a ****load of ICs and the same thing happens that is worse.

If it is a software thing, I got the EPROM copier and if it is likely to 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 ****. (I **** you not, there are articles on that, in fact should I put a foil tape on top ?)

And what if I get cheap EPROMs and they go bad ?

Well, that's the question. Start flashing the chips I got or get new ones ? Note that we also got rush jobs. Not really rush but they have been there long enough.


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 ****". 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.


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Old January 8th 16, 07:10 PM posted to sci.electronics.repair
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Default Seeking Opinon on EPROM Problems

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.
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Old January 11th 16, 09:04 PM posted to sci.electronics.repair
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Default Seeking Opinon on EPROM Problems

whit3rd wrote:
I wouldn't waste time erasing/reburning old parts (are they UV EPROMs, or flash, or EEPROM?), I'd just
program a flash replacement. The parts are cheap enough, and 'the better part of a day' is not.


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.


--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379

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Old January 12th 16, 06:02 AM posted to sci.electronics.repair
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On Monday, January 11, 2016 at 12:04:07 PM UTC-8, Geoffrey S. Mendelson wrote:
whit3rd wrote:
I wouldn't waste time erasing/reburning old parts (are they UV EPROMs, or flash, or EEPROM?), I'd just
program a flash replacement. The parts are cheap enough, and 'the better part of a day' is not.


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.


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.


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