MAC-42 Posted August 21, 2014 Share Posted August 21, 2014 I picked up my 600XL on eBay some months ago. It wasn't working at the time; I needed to replace the PIA chip to get it functioning again. All seemed well at 16k after that, but I wanted to upgrade it to 64k. Following the instructions I found here, I bent the appropriate pins, soldered wires between them and the appropriate pads on the board...and it worked. Or so I thought. Periodically, after being left on for a while whether I'm using it or not--I use it almost exclusively for programming rather than for gaming--characters would appear on the screen at random locations. Sometimes the screen would have a few of these scattered around, while other times would see the screen covered in gobbledygook. Each time, the computer would freeze and need to be powered down. I undid my work, cleaned it up and redid it, especially around the pads on the board. (I'm modest at best with a soldering iron, and those pads are mighty close together.) Same problem. I've confirmed that the correct pins are bent up and the correct pads are connected up, so I can eliminate that much human error in this mess. I haven't tried reversing the upgrade to see if this improves things. To be frank, I'm not sure that this was in full working order at 16k as I never really used it much in that configuration. Maybe there were more extensive problems than just a bad PIA when the machine arrived. Anyway, I thought I'd post the latest bunch of stuff that appeared on the screen and see what anybody can make of it. Quote Link to comment Share on other sites More sharing options...
Rybags Posted August 21, 2014 Share Posted August 21, 2014 The Ram itself might be bad. You can install the Ram chips without doing any of the other upgrade process - that's what I did initially. You can then verify that 16K of it actually works, then do the rest of the process. Note there was a "wrong" procedure floating around, but I'd guess if you took instructions from here they should be right. There's always the chance the problem is somewhere else, but if the machine was stable with 16K then it tends to point to something you added. I should think if you bungled the other stuff that the machine wouldn't work properly at all. Do the Ram chips get hot? Also, do you have another XL you can swap parts from? Maybe try the PIA, MMU and CPU from another machine. 1 Quote Link to comment Share on other sites More sharing options...
MAC-42 Posted August 21, 2014 Author Share Posted August 21, 2014 The Ram itself might be bad. You can install the Ram chips without doing any of the other upgrade process - that's what I did initially. You can then verify that 16K of it actually works, then do the rest of the process. Note there was a "wrong" procedure floating around, but I'd guess if you took instructions from here they should be right. There's always the chance the problem is somewhere else, but if the machine was stable with 16K then it tends to point to something you added. I should think if you bungled the other stuff that the machine wouldn't work properly at all. Do the Ram chips get hot? Also, do you have another XL you can swap parts from? Maybe try the PIA, MMU and CPU from another machine. I actually ran computer with the 4464s plugged in to confirmed that they worked in the unmodified configuration...of course, I didn't run them very long, either. I suppose you may be right that the RAM itself is bad. The RAM chips aren't hot--none of the chips get unduly warm, in fact. I still have the original 4416s; can I plug these back in in the modified configuration and get the system running at 16k? I found the instructions in a post here, yes. I think it was sloopy who posted the one I used, and I confirmed it against other versions floating around online. Should be fine there. I don't have any other XLs, but I did pick up an MMU at the same time as the replacement PIA. Never have used it as all seemed right after replacing the PIA. I can swap it in to see what happens, though. Thanks very much for your thoughts, Rybags. Quote Link to comment Share on other sites More sharing options...
ClausB Posted August 21, 2014 Share Posted August 21, 2014 Is the RAM socketed? Did you solder any chips directly? Did you use static protection? What is the full part number of the 4464s? Quote Link to comment Share on other sites More sharing options...
russg Posted August 22, 2014 Share Posted August 22, 2014 (edited) I picked up my 600XL on eBay some months ago. It wasn't working at the time; I needed to replace the PIA chip to get it functioning again. All seemed well at 16k after that, but I wanted to upgrade it to 64k. Following the instructions I found here, I bent the appropriate pins, soldered wires between them and the appropriate pads on the board...and it worked. Or so I thought. Periodically, after being left on for a while whether I'm using it or not--I use it almost exclusively for programming rather than for gaming--characters would appear on the screen at random locations. Sometimes the screen would have a few of these scattered around, while other times would see the screen covered in gobbledygook. Each time, the computer would freeze and need to be powered down. I undid my work, cleaned it up and redid it, especially around the pads on the board. (I'm modest at best with a soldering iron, and those pads are mighty close together.) Same problem. I've confirmed that the correct pins are bent up and the correct pads are connected up, so I can eliminate that much human error in this mess. I haven't tried reversing the upgrade to see if this improves things. To be frank, I'm not sure that this was in full working order at 16k as I never really used it much in that configuration. Maybe there were more extensive problems than just a bad PIA when the machine arrived. Anyway, I thought I'd post the latest bunch of stuff that appeared on the screen and see what anybody can make of it. I can't make anything of your screen. Antic and GTIA are major display chips. My solution is to swap chips, but you'd need a working, socketed motherboard to do that. You don't give your location, so I probably don't live where you could bring your 600XL over. I"ve thought of a 'LIBRARY' socketed 800XL mb. But the shipping and deposit would cost more than a new computer from Ebay/Best/B&C/Craig's List/etc. As my ID says, I live in Cleveland, Ohio. Edited August 22, 2014 by russg Quote Link to comment Share on other sites More sharing options...
Rybags Posted August 22, 2014 Share Posted August 22, 2014 If you put the 16K ones back in, the system will still see it as 64K - likely the system won't be able to start up normally. Quote Link to comment Share on other sites More sharing options...
MAC-42 Posted August 22, 2014 Author Share Posted August 22, 2014 Is the RAM socketed? Did you solder any chips directly? Did you use static protection? What is the full part number of the 4464s? The motherboard is socketed, so there was no need to directly solder chips. I do keep myself grounded. The 4464s are TMS4464-15NL; my original 4416s were TMS4416-15NL. For whatever it's worth, the RAM always checks out on the self-test. I've left that running with the 4464s for ages at a time and never had it report a problem. Guess it depends on how good the self-test RAM checks are. Quote Link to comment Share on other sites More sharing options...
MAC-42 Posted August 22, 2014 Author Share Posted August 22, 2014 As my ID says, I live in Cleveland, Ohio. Yeah, I'm down in Florida. Not exactly just around the corner, sadly. Thanks for the offer, though. Quote Link to comment Share on other sites More sharing options...
MAC-42 Posted October 5, 2014 Author Share Posted October 5, 2014 Just posting an update (and, hopefully, a possible resolution) to this post. I obtained a 600XL with known-to-be-working chips this weekend. The first thing I did was to remove the ANTIC from the original (the upgraded, problematic one) and replace it with the ANTIC from the new one. It's given me a good excuse to play games and code all afternoon as I wait to see if things go wrong. I'm about 4.5 hours into running this new configuration without problems. Usually, I would see things going wrong by now. With a bit of luck, I might have a solution to the problem. If that's not it, well, we'll move on to the GTIA and try again. Quote Link to comment Share on other sites More sharing options...
Paul Westphal Posted October 7, 2014 Share Posted October 7, 2014 All 600xl's are socketed and HongKong 800xl's are to. Pick one up off ebay for parts, cheap. Quote Link to comment Share on other sites More sharing options...
MAC-42 Posted October 7, 2014 Author Share Posted October 7, 2014 (edited) All 600xl's are socketed and HongKong 800xl's are to. Pick one up off ebay for parts, cheap. That's what ended up happening. All is well now, and I have spare chips as far as the eye can see now. My last post was just a note for anyone down the line who encounters something similar. Edited October 7, 2014 by MAC-42 Quote Link to comment Share on other sites More sharing options...
rockdoc2010 Posted January 21, 2015 Share Posted January 21, 2015 well i had the same problem! infant mortality did the 64k upgrade and all was good turned the system back on and i got tearing of video on right side of screen also got shift of red and blue when doing the self test it didnt work! i swapped all the sugested chips.. no joy i moved the upgrade to a new 600xl , and it all worked as advertized! Flawless IT IS WINTER AND I DO HAVE CATS Quote Link to comment Share on other sites More sharing options...
repetto74 Posted April 2, 2017 Share Posted April 2, 2017 I am having exactly the same problem with my 600XL!! I did the upgrade to 64k and was working really good for a few days then suddenly it started putting garbage characters on screen and then the same garbage as in the picture (with screen rolling up and down). I do have replaced both rams (already new as for used to mod the machine to 64k) with two new ones but no luck. In my case the freeze will pop up after a few minutes from cold power up. My rams are labelled 41464C-12 and were confirmed compatible. I have already swapped 64K RAMS/GTIA/ANTIC/CPU/PIA and POKEY with no luck. MMU runs very hot quickly (C061618 in U2) it may be suspicious but where I may find a replacement for it? I did not try to revert to the original 16K config, I may want to try but need then to dig out also the TTL marked 74LS51 in U16 as the leg has been broken during the mod and just a wire soldered now (cannot make this pin to contact the socket anymore). Would really like to fix this. Quote Link to comment Share on other sites More sharing options...
R.Cade Posted April 2, 2017 Share Posted April 2, 2017 You can replace the MMU with a modern 16v8 GAL that runs cool. Most newer EPROM burners will handle them... Quote Link to comment Share on other sites More sharing options...
repetto74 Posted April 2, 2017 Share Posted April 2, 2017 Sounds interesting :-). Is the binary available for burning it into the 16V8GAL? Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted April 3, 2017 Share Posted April 3, 2017 Sounds interesting :-). Is the binary available for burning it into the 16V8GAL? mmupal.zip Quote Link to comment Share on other sites More sharing options...
repetto74 Posted April 3, 2017 Share Posted April 3, 2017 Hi Flashjazzcat ! Million Thanks ? Quote Link to comment Share on other sites More sharing options...
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