Shift838 Posted March 31, 2023 Share Posted March 31, 2023 (edited) I was able to secure a 1200xl that looked to be in good shape, however upon trying to boot I get the black screen when powered on. I know the cable is good, i know the voltage regulators within the 1200xl are outputting 5v. I have reseated all the chips as they are all socketed. Still no go.. Tested all the DRAM chips with a DRAM tester and they all passed. I have left the unit powered up to see if any of the RAM chips are getting hot and they are not, but i did find the DMPAL16L8 is getting quite a bit hotter than any other chip. Could this be the culprit? If so, where can I get one of these (I don't even know what this PAL is doing since i am pretty new to the ATARI). If it can be replaced, can it be replaced with a GAL and if so which one and where do I get the file to program it? Edited March 31, 2023 by Shift838 Quote Link to comment Share on other sites More sharing options...
Beeblebrox Posted March 31, 2023 Share Posted March 31, 2023 (edited) It could also simply be a dead cpu. Plus just because ram chips are testing OK doesn't mean there aren't bad sockets, cold solder joints, etc etc. Post a few hi res images of the top and underside of the board as a start. Edited March 31, 2023 by Beeblebrox Quote Link to comment Share on other sites More sharing options...
Shift838 Posted March 31, 2023 Author Share Posted March 31, 2023 i'll get a few pics. I also tried to swap the Pokey and the C012294 but still the same issue. Quote Link to comment Share on other sites More sharing options...
Shift838 Posted March 31, 2023 Author Share Posted March 31, 2023 Here are a couple of pics of the board. Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted March 31, 2023 Share Posted March 31, 2023 (edited) transistor can behind rf modulator on pcb riser looks corroded clean flux off PCB so we can see if they are bridged etc. might be conductive residue in there. make sure VIA s are filled in... Edited March 31, 2023 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
Shift838 Posted March 31, 2023 Author Share Posted March 31, 2023 4 minutes ago, _The Doctor__ said: transistor can behind rf modulator on pcb riser looks corroded is that part of the rf modulator? if so, i'm not using it. I have a composite monitor cable and svideo monitor cable. Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted March 31, 2023 Share Posted March 31, 2023 (edited) did you catch the rest of the list? Edited March 31, 2023 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted March 31, 2023 Share Posted March 31, 2023 9 minutes ago, Shift838 said: is that part of the rf modulator? if so, i'm not using it. I have a composite monitor cable and svideo monitor cable. And you are sure the cable is wired properly for Atari's 5 pin? Do you get any sound when you turn the unit on? Quote Link to comment Share on other sites More sharing options...
Shift838 Posted March 31, 2023 Author Share Posted March 31, 2023 9 minutes ago, kheller2 said: And you are sure the cable is wired properly for Atari's 5 pin? Do you get any sound when you turn the unit on? the cable works on my 800XL no problem. Quote Link to comment Share on other sites More sharing options...
Shift838 Posted March 31, 2023 Author Share Posted March 31, 2023 26 minutes ago, _The Doctor__ said: transistor can behind rf modulator on pcb riser looks corroded clean flux off PCB so we can see if they are bridged etc. might be conductive residue in there. make sure VIA s are filled in... i'll be working on the rest of this list later this evening. Quote Link to comment Share on other sites More sharing options...
Shift838 Posted March 31, 2023 Author Share Posted March 31, 2023 Looking at some photos in the internet and all the photos of the 1200XL show a different IC for the MMU. this 1200XL has a PAL in the MMU socket, wonder why.. Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted March 31, 2023 Share Posted March 31, 2023 That is the correct MMU for the 1200XL Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted March 31, 2023 Share Posted March 31, 2023 the MMU in the 1200XL is diff'rent to the other XL/XE models - not interchangeable Quote Link to comment Share on other sites More sharing options...
Shift838 Posted April 1, 2023 Author Share Posted April 1, 2023 (edited) 4 hours ago, kheller2 said: That is the correct MMU for the 1200XL this MMU seems to get pretty hot, much hotter than any other IC on the board, so I am wondering if it is bad. Is the 1200XL MMU code available to be programmed to a GAL somewhere? I have some GAL IC's that I can use. I know many people have ripped the 1200 MMU/OS out and gone back to the 800XL for the best compatibility but before I decided to do that, i want to at least see it boot.. Edited April 1, 2023 by Shift838 Quote Link to comment Share on other sites More sharing options...
+bob1200xl Posted April 1, 2023 Share Posted April 1, 2023 The first thing that happens on any Atari is RESET. If you aren't getting flashes and clicks when you power on, you may have a stuck RESET line. Can you measure RESET after you power on? It should be >>4v on pin 40 of the CPU. U16 drives RESET. Unplug the keyboard. The MMU runs hotter than the other chips. xxx609 is 1200XL xxx618 is 800XL. Bob Quote Link to comment Share on other sites More sharing options...
Shift838 Posted April 1, 2023 Author Share Posted April 1, 2023 So i found the issue. It's a dead PIA C014795-12. I swapped it out with a good one out of my 800XL since it uses the same IC and bam. So does anyone have a spare PIA C014795-12 they are willing to part with? PM me.. 2 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted April 1, 2023 Share Posted April 1, 2023 (edited) Synertek P6520A It's just a garden variety 6520 you could probably even use a 65B21 MC68B21P Edited April 1, 2023 by _The Doctor__ 2 Quote Link to comment Share on other sites More sharing options...
Shift838 Posted April 1, 2023 Author Share Posted April 1, 2023 22 minutes ago, _The Doctor__ said: Synertek P6520A It's just a garden variety 6520 you could probably even use a 6521 I fount a couple of the Synertek P6520A chips for about $2.00 each. Ordered and will see. 3 Quote Link to comment Share on other sites More sharing options...
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