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The mT RAM investigation thread. Show yours, good or bad....


Level42
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I'd like to do some investigation if there might have been just a certain batch of bad mT RAM chips that got into 800XLs and XE machines.

 

The datecoding isn't immediately obvious but maybe we can find some patterns....

 

I'd like to see pictures of the full,sets (if on board) wether good working or bad.

 

Please specifiy GOOD or BAD and the number which I think is a datecode like here, 431 and 438.

 

Here's a set that has been working fine in Fred_M's 800XL which he bought in 1984 or so, it had the VLSI,s directly soldered so must be Tramiel era I guess.

 

GOOD-431 and 433:

post-25272-0-28890400-1514468860_thumb.jpg

Edited by Level42
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Dear Level42,

 

it doesn't look like a bad batch to me.

On the Commodore site (uhh ohhh evil I know)

where a lot of μT Ram Chips used.

I repaired a lot of c64 boards.

As a general rule: is it a μT, it is probably

dead, is it a different ram chip, it is most likely in good condition.

So, it must be a general problem with the

rams made by that company.

 

Stefan

Edited by Stefan Both
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I agree about that Stefan but _maybe_ ....just _maybe_ .....because the pic I showed is Fred_M's original first 800XL....and still working fine....so not ALL mT's die.

 

I have a 130XE with all mT's (except the usual top left position of course) that also works just fine....

 

I'll continue posting pics as I go along and find more mT's .....good or bad......, even if it's just for me :)

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My original 800XL is still working just fine. Probably purchased around the same time (1984-ish) - mT memory is all good.

 

I have also had several 800XL's, 65XE's and 130XE's pass thru my hands. The only one's I had issues with were the 65XE's and mT chips were bad. Replaced all with socketed and just replaced the bad memory with original mT chips I had. The 800XL's and 130XE's were just fine, but can't recall if all of them had mT or not.

Edited by NISMOPC
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I have a non working 130XE here that I got on eBay about 5 years ago. Haven't investigated cause of it's problem (full white screen on powerup from memory) so it's not necessarily bad Ram, possibly it's the CPU.

 

It's got a single Sharp (8629) LH2164-12 at the top left.

The remaining chips in the left bank are all MT 4264-12 (8722)

On the right bank, the chips are the same MT except the 5th one down which is date (8726)..

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Great to hear guys but please....pictures or at least check the datecodes on all the chips ....please :)

I posted a picture the last time you got a bee in your bonnet regarding mT ram, in that thread looking for one different chip on a board otherwise filled with mT. I’ll post it again tonight if you still need it.
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Here's my own trusty 130XE (which I just retrobrighted.....looks like factory fresh) RAM.

 

All mT except the usual top left position and three different datecodes:

 

450

501

8503

8504

 

Actually, a very interesting and helpful set I have there !!!

 

It very much looks like mT used a three digit datecode first, so 450 would be week 50 of 1984, and 501 would be week 1 of 1985.

Then....it seems mT had some new-year resolution and decided to add the 8 before the previous way of coding, so the 8503 is obviously week 3 of 1985 and naturally 8504 week 4 of 1985.

 

It's interesting and makes sense since these productionweeks are pretty close to each other. I can see that maybe production stopped in the last two weeks or so because of X-mas and new year break....not sure but would make sens...so probably there are no RAMs with week 52, maybe even 51 or....this could be just random.

 

Even so, they are pretty close to each other in production date.

post-25272-0-31429400-1515196521_thumb.jpg

Edited by Level42
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By the way, the NEC has datecode 8445, so not very much off from the dates of the MTs. That leads me to believe that Atari ordered (considerably less amounts of) NEC RAMs at the same time as they did mTs......in other words.....this is another indication they knew what they were doing and the different brand RAM on top,left is very deliberate and not random thing.

 

Of course, this is just one machine so....the more pics/info, the more we could conclude from this....

Edited by Level42
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My original 800XL is still working just fine. Probably purchased around the same time (1984-ish) - mT memory is all good.

 

I have also had several 800XL's, 65XE's and 130XE's pass thru my hands. The only one's I had issues with were the 65XE's and mT chips were bad. Replaced all with socketed and just replaced the bad memory with original mT chips I had. The 800XL's and 130XE's were just fine, but can't recall if all of them had mT or not.

 

Well....I'd love to see any pictures if you have them, at least of your original 800XL, or at least all the datecodes of those RAMs.

 

Now....AFAIR, when Tramiel took over, the 800XL was either kept in production or maybe started up again a bit later...and the first XE was the 130XE. The 65XE's came later....this might be an indication that earlier mTs might be just fine....we need more data :):)

Edited by Level42
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Picture of the spare 130XE board I fixed earlier in another thread.

 

ALL RAMs were dead.....every single one INCLUDING the NEC.

 

To me this is an indication that this machine was fed with too high voltage from a bad or C64 power supply.

Even with mT RAMs that die of natural cause, I have not seen ALL mT RAMs to be bad, and usually the single different brand one is always fine.

 

Nevertheless....here's the picture....

 

Datecodes 8503, 8504 and 8505. So at least they keep the 4 digit datecode.

The NEC has 8447....another indication that the datecodes look to be running pretty much in parallel between the NECs and mT's......

post-25272-0-83465200-1515198001.jpg

Edited by Level42
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I posted a picture the last time you got a bee in your bonnet regarding mT ram, in that thread looking for one different chip on a board otherwise filled with mT. I’ll post it again tonight if you still need it.

Didn't find the picture, can you please post it here, thanks !

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Didn't find the picture, can you please post it here, thanks !

 

Here you go. All good last time I powered it up (last year sometime). Machine needs a Mylar repair for the keyboard but the RAM passes the self test. I've never run any of the more comprehensive memory tests on it.

 

post-30400-0-03203800-1515201961_thumb.jpg

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go to the thread for editing privs...

 

http://atariage.com/forums/topic/135961-important-note-regarding-post-editing/?p=1641211

 

you ask for the priv and state why it's needed and it may be granted.

 

 

Thanks for that tip Doctor !

 

Or just pony up a few bucks to help Albert keep the lights on to become a Subscriber and then you can edit for MUCH longer. :)

 

(Just being snarky - you *can* edit for much longer but you will need special privileges for a post older than a day or two, I think.)

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