4116 RAM Tester

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DDE
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4116 RAM Tester

Fellow Hobbyists,

 

Hi, I’m new here, but I’ll been reading this forum for years.  I’ve been looking for a good way to test the ram on my various Apple II’s, Clone, and 16K RAM cards.  Since I didn’t find a readymade solution, I decided to create my own and I would like your thoughts on this project.  It is based on the work of several others:

https://www.youtube.com/watch?v=MVZYB54VD2g

https://forum.defence-force.org/viewtopic.php?p=15035&sid=17bf402b9c2fd97c8779668b8dde2044

To keep it simple, I use a step-up voltage module and a reverse voltage module.  It’s powered through the Nano (I covered the Nano LEDs as I find these really annoying).  It seems to work well, and after testing almost a hundred ram chips, I found several bad on an unused 16K card I have.  I totaled up the parts cost, and it’s around $18.

Thanks,

DDE

 

macnoyd's picture
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It looks like you've done a good job of it

It looks like you've done a good job of it. 

Are you planning on selling the PCB's?

DDE
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4116 Ram Tester

Hi, yes, eventually. But I'm really looking to help support the vintage computer community (Apple II) as so many others have (and so many on this forum have).

-DDE

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Really cool !

Could it be easily adapted to test the 4K x 1 RAM chips found in the Apple I ?

 

(During the past 4 months my own Apple I build was blocked most of the time by running DRAM tests. So far I found 1 truly bad DRAM (which even spat into the bus so that the monitor program produced lots of superflous stars but almost worked) and 6 suspect / flakey ones out of more than 200 of various brands (Intel, Mostek, Motorola). 

 

Seems that 40+ year old NOS DRAM really need some thorough testing !

 

Beware that some of the faults / bit disturbances take a lot of observation time to find (I use 1 week running Mike Willegals RAM test 24/7).

 

Back in the day when the radiation sensitiviy issue with DRAMs was discovered (around early 1980s ???) some daring engineers used DRAMs as an altimeter and it worked  well enough to marvel at the perils of living at high altitude.

 

Anyway, if you make PCBs please consider to test 4k x 1 and 64k x 1 DRAMs, too.  And some option to run tests for a long time without any user intervention.

 

Of course there are lots of other DRAMs. But for 1970/80s vintage microcomputers the 4k x 1, 16k x1, and 64k x 1 as used in the Apple I, II, IIc ... will cover a lot of ground. 

 

 

 

 

 

 

 

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