TroyQ Posted December 3, 2017 Author Share Posted December 3, 2017 Small update: Start off with the "troubleshooting" section in the service manual & also download a TTL logic data book. This really helped me fix my 65XE. http://blog.3b2.sk/igi/post/Sams-Computer-Facts-ATARI-130XE.aspx I use the same logic probe for checking stuff quickly but a scope is more ideal ( it's better than nothing I guess ). Also, a logic comparator or EPROM device programmer with TTL logic / RAM test will go a long way. I have an EETools TopMax which is great for checking mask roms / EPROMs , TTL logic and different types of RAM but it's quite expensive. I don't know what I'd do without it. Super big thanks for this link! I didn't see it at first, but I found the logic table for all the ICs in that PDF. I have been busy, so only had a chance to do an initial sanity check of "am I using the logic probe correctly and getting accurate results" Looks like I am. I tested FREDDIE against the Logic Chart in the PDF and had 3 discrepancies: pin 21 should pulse and I get low, pins 34 & 38 should pulse and I get high. Pin 21 is A12, pin38 is R/W and pin 34 goes to pins 3 on DRAM (if I understand the schematic correctly). I know I need to do some more testing, but that to me looks like the issue is memory subsystem related. An address line (A12) is stuck low and the R/W is stuck high (trying to write?). RAM or FREDDIE I am guessing? Quote Link to comment Share on other sites More sharing options...
Level42 Posted December 3, 2017 Share Posted December 3, 2017 I already told you what I think it is.... 1 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted December 3, 2017 Share Posted December 3, 2017 almost all dead 130's I have repaired had bad ram in particular most non working Ataris had that or MMU problem... some had bad support chip rarely did I have a dead Fred.. lastly were the big chips.. there was a thread the indicated what was dead based on video color or symptoms at one time not sure if it was here on AA but it was surprisingly good at times... red tint or screen, blue tint or screen, black screen, screen that flashed, garbage on screen (variants of garbage on screen) etc etc... 1 Quote Link to comment Share on other sites More sharing options...
1050 Posted December 4, 2017 Share Posted December 4, 2017 I know I need to do some more testing, but that to me looks like the issue is memory subsystem related. An address line (A12) is stuck low and the R/W is stuck high (trying to write?). RAM or FREDDIE I am guessing?No smoking gun is my take away so far. FREDDIE appears to be working and stuck trying to read a lower address. The bar over the top of the WRT of ram pin 3 indicates a write happens with negative assertion. /WRT also means this same thing. /CAS, /RAS as well, both are high until those signals are brought low to assert them. So R/W is both a contraction and logical state declaration which can be taken for just a contraction using a forward slash by the casual reader. /WR would be confusing and not nearly as sexy. Hexy? For the moment I would move on to the cheaper or easier to replace MMU/OS Rom looking for non- functional chips if one can be found first. No joy there then socket and replace ram to try again. A 2nd machine could be testing the ram removed looking for bad ones. I certainly don't see a dead FREDDIE if shoestring's post #48 excellent advice flies in an upright manner. Quote Link to comment Share on other sites More sharing options...
TroyQ Posted December 30, 2017 Author Share Posted December 30, 2017 Its been a bit since I've been able to do any troubleshooting on this but I've finally had the time and I've found a solution: Bad ANTIC chip. Things it was not: Bad RAM ** (replacing the RAM did not fix the failure, but afterwards, the logic probe produced accurate results on the FREDDIE chip - so it is possible there were also bad RAM) Bad CPU Bad GTIA Bad 10uF or 22uF caps I think I got lucky with my 130XE board in that it was not too much trouble desoldering / adding sockets. By my count, I did 452 pins total and no lifted traces or anything bad. I now have a mostly socketed motherboard. I may still socket the rest of the chips and replace the 4.7uF & 470 uF caps just to satisfy my own OCD-ness. I saw there is another thread for tracking good/bad Mt RAM. I'll put the original ram back in and post the results and pix there. Again, thanks to everyone and their advice on this. 5 Quote Link to comment Share on other sites More sharing options...
Level42 Posted December 30, 2017 Share Posted December 30, 2017 (edited) Wow....great you persisted and got it fixed !!! Yeah Id love to know about the old RAM bu be careful if there are anynsolder rests on the pins they might damage your brand new sockets,,, Edited December 30, 2017 by Level42 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted December 30, 2017 Share Posted December 30, 2017 Congratulations! There's nothing quite so satisfying as pulling a machine back from the dead with your own hard work and perseverance! Quote Link to comment Share on other sites More sharing options...
Spanner Posted December 30, 2017 Share Posted December 30, 2017 (edited) Great well done,I have a 130XE too that I use,Got it in the 90s,I have a 800XL but some of the keys don't work on the keyboard,like that better. Edited December 30, 2017 by Spanner Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted December 30, 2017 Share Posted December 30, 2017 800XL keyboards--- the more you use them the better they work 1 Quote Link to comment Share on other sites More sharing options...
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