eprom question

coinopjunkie

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I want to replace some eproms with the code tmm275120-25 do I need to get the same ones or are other compatible? This is for a road blasters PCB with corrupted eproms if that matters.
 
You should be able to replace these with any 27512 series eprom. The pinouts will be the same.
 
Just make sure the # after the dash is the same or lower (-25, -20, -17, -15, etc....)

You can also use 27C512 EPROMs too...
 
another question

Just make sure the # after the dash is the same or lower (-25, -20, -17, -15, etc....)

You can also use 27C512 EPROMs too...

If an eprom won't erase does that mean its bad? and I found a tms27c512JL in my junk pile but does not have a -25,-20 etc it does say LDQ 8839 but I think that is a date code? Will this work ?
 
If an eprom won't erase does that mean its bad?

Sometimes. Usually it just means that you didn't clean the window well enough. Just a tiny bit of goo is all that's required to block the UV light getting to one tiny area, and it'll fail the blank check. I've even had a few chips where the window had a bubble or defect in it, which requires erasing the chip at an angle to get the rest of the die exposed. There were also a few where the die was bigger than the window - also requiring contortions to erase.

I've also had a couple old chips that were stubborn to erase. Program the chip with all 00's, which you can do no matter what is currently on it. If it fails to program/verify, then it's definitely a bad chip - but it should program. Then erase it. If it won't blank check, read it back in and see how much the data is changing - see if it's getting blank.

But yeah, it might just be a bad chip.

-Ian
 
Justing putting in my two cents, the -25 and the -20 are the speed at which the EPROM can read the data, so you always want something that is the same OR faster. Just wanted to point that out to anyone else looking at this thread.

Yeah I usually use Goo Gone to clean the window on my EPROMs when I can't get them erase completely. Use a little bit of goo gone and then a bit of windex and I'm good to go. I have had some old EPROMs that just go bad, but I think I've only encountered 2 or 3 out of all the ones I have ever tried programming.
 
not listed

Maybe.

Look up the data sheet for it at http://www.datasheetarchive.com and see what the speed values are for a version of chip that doesn't have it labeled.

RJ

Thats funny my chip manufacture is not listed mine is made by texas instruments. I would think that I would need a spec sheet specific to that maker right?
 
Thanks

Justing putting in my two cents, the -25 and the -20 are the speed at which the EPROM can read the data, so you always want something that is the same OR faster. Just wanted to point that out to anyone else looking at this thread.

Yeah I usually use Goo Gone to clean the window on my EPROMs when I can't get them erase completely. Use a little bit of goo gone and then a bit of windex and I'm good to go. I have had some old EPROMs that just go bad, but I think I've only encountered 2 or 3 out of all the ones I have ever tried programming.

So is the lower the number the faster it reads ? Funny thing to me at least, the reason I read and compared all these chips were for missing graphics on my game, when I first read this chip it read fine but did not compare to the dump so I tried to erase it now it comes up with an error saying it does not recognize the chip under that description, so I think that chip is done?
 
So is the lower the number the faster it reads ? Funny thing to me at least,
The number is the access time in nanoseconds. The lower the number, the fewer nanoseconds it takes to read the data, and thus the faster it is.

I tried to erase it now it comes up with an error saying it does not recognize the chip under that description, so I think that chip is done?

What do you mean by this? Does it give you this error when you try to program the chip, or does it give you this error when you try to blank check it? Are you sure you have the correct chip selected in the programmer software? Can you program the chip full of 00's?

-Ian
 
The number is the access time in nanoseconds. The lower the number, the fewer nanoseconds it takes to read the data, and thus the faster it is.



What do you mean by this? Does it give you this error when you try to program the chip, or does it give you this error when you try to blank check it? Are you sure you have the correct chip selected in the programmer software? Can you program the chip full of 00's?

-Ian

It errors when you put the chip in or blank check it or try and program it. Anytime you send any command it tells you that the chip is not what device you selected you can hit ignore but none of the other chips give this error and this one didn't use to either. Yes I'm positive I put the chip in correct.
 
if your programmer is OK with other chips but gives errors on your chip and you selected the right chip from the programmers menu. then the chip is probably bad or there is corrosion etc on the pins that is causing problems. You might try cleaning the chip first, but if that does not work you can always get a new chip 27C512s NOS and used 27C512 are pretty cheap on ebay.
 
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