Super Stand Alone System Test shows errors?

+xucaen · July 21, 2018

... although I could use some tips for finding the correct IC extraction tool.. I had no idea remove an IC could be so complicated. o_O

+DrVenkman · July 21, 2018

IC removal is easy for socketed boards, which yours is. Just take a very small flat blade screwdriver (I use a jeweler's screwedriver) and slide it just a little way under one side of the chip between the bottom of the chip and the socket, then twist gently. It will rock that end of the chip up a tiny bit. Repeat on the other side, going slowly. Repeat once or twice alternating each side and the chip will come out. If you use too much force, it'll lift completely from one side and bend the legs on the other side. Easy peasy.

Edited July 21, 2018 by DrVenkman

+xucaen · August 2, 2018

Reseat all the chips first if they are socketed. Almost sounds like a thermal issue, (if not a power issue). Does it pass the test fine after being cold?

I was just re-reading this thread, and just wanted to ask about passing the test when cold...

What happens is, I turn on the 800xl and run the memory test. Everything seems find, then after about 5 minutes the ROM bars turn red. If I turn it off and back on again same thing - looks fine for about 5 minutes then the ROM bars turn red...

Question: would the chips cool down that quickly if I just turn it off and on again? If this were a heating problem I would expect the ROM bars to be red after shutting it off and on... that's what I wanted to ask.. what do you think?

I inquired to Best Electronics about replacing the chips and he mentioned that these chips usually do not fail. so now I am wondering if it could be something else...

Cheers.

+xucaen · August 2, 2018

U2 is a bog-standard 74LS138N logic chip. Any electronics retailer should have them. Mouser has them for 84 cents apiece, about 65 cents in quantities of ten. Shipping will kill you though. I'm sire Digi-Key and the other electronics stores are about the same.

The others are Atari-specific. Best Electronics will have them. Shoot them an email and ask for pricing and payment info.

EDIT: misunderstood your question. U3 is the MMU. It's directly underneath the cartridge connector. U2 is the 74LS138N chip directly below that one. They're common to every 800XL board revision, so far as I know.

Actually, your information is very helpful!

I think I found the logic chip on digikey, thanks for the tip. I don't usually do this sort of thing so I never know what to look for (I'm a software engineer, not an electronics engineer ;-) )