russg Posted February 25, 2014 Share Posted February 25, 2014 (edited) The memory came today but as was foreshadowed, it did not fix the problem. Still same problem as before. Oh well. I did a "push check" on each IC - making sure they were all solid. Interesting result - pushing on U17 made the system work better for a short time. Immediately after pushing on U17 I had 2 successful boots before it failed again. U17 is labeled 1100008-01 which is the GTIA. Separate Note - the chip that originally had a bent pin was U22 - C012294-19 which is Pokey. I had found either pin 20 or 21 was bent under the IC and not making contact. I have since straightened it and made sure it is seated OK. That would be /K2 or /K3 as per schematic. That would cause issues with Keyboard scan. This could not have passed initial burn in that way. Must have been replaced by an owner, and done poorly. In summary, I should start next with trying to swap these 2: U17 - since physical motion affects its behavior. U22 - since the prior owner was running it with one pin open-circuit for who knows how long. Is there any commonality with the 400? I have a dead 400 I could rob. Looks like I could steal both of them (depending on whether I have a GTIA or CTIA) - A101 / Pokey is on the motherboard, and A301 is the CTIA/GTIA on the CPU board. A CTIA should be OK, at least for testing. The POKEY from the 400 should be OK. You don't know if the 400 chips are sound. I have made a 'test' 800XL, fully functional and fully socketed. Just the motherboard, no case or keyboard. I guess PM me if you're interested. I'd say it would fit in a USPS Priority mail box. It would cost more to ship than just the 40 pin LSIs. I wish I new more theory of operation. The 130XE Sam's Computerfacts in a recent post would give instructions on troubleshooting. Your GTIA sounds promising. The chip ID are the CO numbers, eg. GTIA CO14805. I can't estimate shipping, but I'm sure it would be more than $15. Best Electronics sells about all the 800XL chips, once you've found the culprit(s). Edited February 25, 2014 by russg Quote Link to comment Share on other sites More sharing options...
ryanr256 Posted February 25, 2014 Share Posted February 25, 2014 Funny. I just messaged him about a Rev. D motherboard I have laying around. It's not socketed though. -Bob Quote Link to comment Share on other sites More sharing options...
russg Posted February 25, 2014 Share Posted February 25, 2014 Funny. I just messaged him about a Rev. D motherboard I have laying around. It's not socketed though. -Bob MIne is a Rev A2. Quote Link to comment Share on other sites More sharing options...
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