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Replacing bad RAM in 130XE

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Hello fellows, so another question about bad RAM in 130xe. I was looking at this product:
https://lotharek.pl/productdetail.php?id=291

But, it only has 64K, and the 130XE has 128K. So, does that mean it would not fix the issue?

My 130XE motherboard has these 2 chips socketed. Not sure which socket that the 64K Lotherek product would go in. Maybe someone here knows?

130xeboard3.jpg

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The SRAM board goes under the CPU (so, the chip at the rear in the photo). The SRAM board should allow the computer to boot and work normally; you will experience issues when accessing extended RAM only if DRAMs in the second bank are bad.

 

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2 hours ago, flashjazzcat said:

The SRAM board goes under the CPU (so, the chip at the rear in the photo). The SRAM board should allow the computer to boot and work normally; you will experience issues when accessing extended RAM only if DRAMs in the second bank are bad.

 

Hello Flash Jazz Cat, I've seen some of your videos on Youtube. Keep up the good work! So, I took a picture of the RAM diagnostic shown below. From what I've read, this only shows there are bad chips in bank 1, and the test doesn't proceed to bank 2 if bank 1 has bad chips.

 

So, if that is correct, both banks might have bad RAM chips. So, my plan would be to buy some RAM chips off Ebay and attempt the piggy back to "fix" the RAM and allow the test to continue to bank 2.

 

If only bank 1 contains bad RAM, I can use Lotharek's 64K chip and the job is done? I think Lotharek's chip would still require some soldering of a few wires, but I should be able to do that even with my old eyesight and shaky soldering hands. I couldn't find any documentation that shows exactly how to install it.

 

Is that all correct? I've posted a pic of the RAM test. Any idea which chips would be bad from the piggy back test? The 130XE has 16 chips.

 

Also, any recommendations for RAM chips on Ebay (make, model, type, and whatnot)?

 

Cheers! Jason.

ramtest.jpg

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Hello Fellows,
 

So, I took a picture of the 130XE RAM diagnostic shown below. From what I've read, this only shows there are bad chips in bank 1, and the test doesn't proceed to bank 2 if bank 1 has bad chips. The 130XE has 128KB of RAM.

 

So, if that is correct, both banks might have bad RAM chips. So, my plan would be to buy some RAM chips off Ebay and attempt the piggy back to "fix" the RAM and allow the test to continue to bank 2.

 

If only bank 1 contains bad RAM, I can use Lotharek's 64K chip and the job is done? But, I'd only have 64K, not the full 128K in the 130XE?

 

I think Lotharek's chip would still require some soldering of a few wires, but I should be able to do that even with my old eyesight and shaky soldering hands. I couldn't find any documentation that shows exactly how to install it. Maybe it doesn't require any soldering.

 

Is that all correct? I've posted a pic of the RAM test. Any idea which chips would be bad from test result? The 130XE has 16 chips.

 

Also, any recommendations for RAM chips on Ebay (make, model, type, and whatnot)?

 

Cheers! Jason.

ramtest.jpg

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If you have the chips to diagnose it, and it works... then use them to replace the chips. No need to go through all the extra trouble and money to fix it then. A simple fix as opposed to something more involved.

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3 minutes ago, _The Doctor__ said:

If you have the chips to diagnose it, and it works... then use them to replace the chips. No need to go through all the extra trouble and money to fix it then. A simple fix as opposed to something more involved.

Thanks for the reply, but I don't have the chips as I don't know which type to use, and per my post, I don't know which chips are bad from the picture I posted. Also, I don't know if Lotharek's 64K chip will disable the remaining 128K in the 130XE RAM.

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Have many RAM chips has your 130XE?

 They are on the left side of the board. Maybe post a picture.

 

Atari RAM will not tel you which chips are bad. You could either use RAM test Eprom or Sys Check cartridge to figure out bad chips

Edited by archeocomp

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11 minutes ago, archeocomp said:

Have many RAM chips has your 130XE?

 They are on the left side of the board. Maybe post a picture.

 

Atari RAM will not tel you which chips are bad. You could either use RAM test Eprom or Sys Check cartridge to figure out bad chips

There are 16 chips.

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33 minutes ago, archeocomp said:

Than you need 4164 type DRAM

http://www.minuszerodegrees.net/memory/4164.htm

 

They can be found super cheap on Aliexpress

 

Also look here at post #5, you can quickly test second bank

https://atariage.com/forums/topic/281132-atari-130xe-4164-best-replacement-or-upgrade-ram-chips/#comments

Ok, thanks. I found this on ebay:

NEC        µPD4164C-15    150 ns    NMOS    N.C.    128cycle/2ms

 

But, the original MT chips have different cycles of 256:

Micron    MT4264-15    150 ns    NMOS    N.C.    256cycle/4ms 

 

No idea what difference that makes, and if NEC is good memory?

 

Also, found this:

T.I. TMS4164-20NL 4164 64K Dynamic RAM

Don't know what "NL" means?

 

Would TI be better than NEC?

 

Thanks.

 

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8 hours ago, jmprice_314159 said:

Ok, thanks. I found this on ebay:

NEC        µPD4164C-15    150 ns    NMOS    N.C.    128cycle/2ms

 

But, the original MT chips have different cycles of 256:

Micron    MT4264-15    150 ns    NMOS    N.C.    256cycle/4ms 

 

No idea what difference that makes, and if NEC is good memory?

 

Also, found this:

T.I. TMS4164-20NL 4164 64K Dynamic RAM

Don't know what "NL" means?

 

Would TI be better than NEC?

 

Thanks.

 

My understanding is that less refresh cycles type DRAM than needed is not harmful, it just means new DRAM will get 256 refresh cycles even though 128 would be enough.

 

Micron is the worst DRAM type, so any other is better. I used NEC as replacement because they do no retain information too long after power off. Power cycling to get computer to initial state (cold reset) requires that you have wait 10 second or even more before you can switch the computer on again if DRAM retains its information too long. Otherwise it will not initialize properly and get stuck thinking DOS or other program is still loaded. That unnecessary waiting nerves.

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Swap the Main and Extended 64K to allow a memory tester like Shoestring's, or Sys-check to test the extended as base RAM 64K by cris-crossing R110 /R111 like so:

474371312_130XESwappedResistors.thumb.jpg.5a31f1e6eccfe8632a62ca5d8641b19d.jpg

This can also be a quick and dirty way to get a non-functional 130XE to boot, if the base 64k is bad, and extended 64K is good.

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