+DrVenkman Posted September 25, 2017 Share Posted September 25, 2017 Here's a pic of the back label: IMG_4101.JPG If this turns out to be some kind or early production model, that will just motivate me that much more to get her up and running again! So no date code on the label. The early <16K serial number and EPROMS for system ROMs makes me think yours is an early example indeed, probably November/December 1982. Any chance there's an assembly date label on the front edge of the board near the keyboard connector? This indicates the board's date of assembly (in this case, Week 14, 1983) Quote Link to comment Share on other sites More sharing options...
Deteacher Posted September 25, 2017 Author Share Posted September 25, 2017 So no date code on the label. The early <16K serial number and EPROMS for system ROMs makes me think yours is an early example indeed, probably November/December 1982. Any chance there's an assembly date label on the front edge of the board near the keyboard connector? This indicates the board's date of assembly (in this case, Week 14, 1983) Assembly Date.jpg There are no date stamps, labels, etc. that I can see anywhere on the motherboard, but I can always take a closer look. Maybe there's something on the underside, but I'll check for that tomorrow. Quote Link to comment Share on other sites More sharing options...
ACML Posted September 25, 2017 Share Posted September 25, 2017 There are no date stamps, labels, etc. that I can see anywhere on the motherboard, but I can always take a closer look. Maybe there's something on the underside, but I'll check for that tomorrow. How did you acquire this unit? Was it from someone from Sunnyvale? Quote Link to comment Share on other sites More sharing options...
Deteacher Posted September 25, 2017 Author Share Posted September 25, 2017 (edited) How did you acquire this unit? Was it from someone from Sunnyvale? I bought it off a guy from Maryland on CL about a year ago. His dad was an electronics repairman and when he died, he had a ton of Atari/Commodore/Tandy/etc. stuff. The 1200xl was packed in original Styrofoam, but did not have the box for it. I don't know if this was new or not, but it was clean as hell. I got it and a bunch of other stuff for cheap. I already had an 800xl, but I'd never heard of the 1200xl so I bought it out of curiosity. When I brought it home, the keyboard didn't work, but I read up on how to clean the mylar, which brought the keys back to life. I'm getting more and more curious about this unit now. Edited September 25, 2017 by Deteacher Quote Link to comment Share on other sites More sharing options...
beamer320i Posted September 25, 2017 Share Posted September 25, 2017 (edited) You might find this video of interest, it's from when Jon (Flashjazzcat) upgraded my 1200XL and found said EPROM's , along with the unusual cartridge connector.. https://www.youtube.com/watch?v=QcovJAqYSE4&t=1s EPROMS, etc are mentioned at 6:45 onwards... Edited September 25, 2017 by beamer320i 4 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted September 25, 2017 Share Posted September 25, 2017 I've had three or four 1200XLs with OS EPROMs through my hands, so didn't consider them especially rare. Never took much notice of the serial numbers, though. Quote Link to comment Share on other sites More sharing options...
Deteacher Posted September 25, 2017 Author Share Posted September 25, 2017 So, I just got off the phone with Best Electronics. He thinks that the 6502 crapped out on me while doing the chip swaps. So, to kill 2 birds with one stone, he's sending me 2 of the 6502s (one for the 1200xl and one for the 5200) along with 8 ram chips for the 5200. He's fairly certain that will bring both machines back to life. I should have my order by the end of the week, so I'll post my results probably this weekend. Thanks for sharing the video, Beamer! I'll definitely sit down and watch it. In spite of these problems, I am learning a lot, so it's not all bad. 3 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted September 26, 2017 Share Posted September 26, 2017 So, I just got off the phone with Best Electronics. He thinks that the 6502 crapped out on me while doing the chip swaps. So, to kill 2 birds with one stone, he's sending me 2 of the 6502s (one for the 1200xl and one for the 5200) along with 8 ram chips for the 5200. He's fairly certain that will bring both machines back to life. I should have my order by the end of the week, so I'll post my results probably this weekend. Thanks for sharing the video, Beamer! I'll definitely sit down and watch it. In spite of these problems, I am learning a lot, so it's not all bad. While you are back in there, can you take a picture of both sides of the 1200XL board. You do have a very early board it seems, especially with EPROM chips in there.. I'm not certain what chips are all original now (5200 vs 1200) to look at some date stamps, but its still an interesting unit. 1 Quote Link to comment Share on other sites More sharing options...
Deteacher Posted September 26, 2017 Author Share Posted September 26, 2017 While you are back in there, can you take a picture of both sides of the 1200XL board. You do have a very early board it seems, especially with EPROM chips in there.. I'm not certain what chips are all original now (5200 vs 1200) to look at some date stamps, but its still an interesting unit. Sure! Won't get to it until the weekend, but absolutely. I'm very curious about this unit, myself and I'll provide all info I can. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted September 26, 2017 Share Posted September 26, 2017 So there's a bunch of oddities in the 1200XL motherboard design that I wonder if we'll ever get to the bottom of. Jon says he's seen a number of 1200XL's with 28-pin EPROMs for system ROMs; I've got three 1200XL's these days, all of them with 24-pin mask ROMs, yet two of the three have 28-pin sockets. The board has a number of jumpers that can be configured in a couple different ways to enable 28-pin or 24-pin ROMs ... That's great and all but one has to ask: why? Why did Atari design a board that can be configured in several ways? Why did they use EPROMs in production machines? Why did they install 28-pin sockets in machines with 24-pin ROMs and sometimes (as in one of mine) only 24-pin sockets? None of this makes a lot of sense for a design that was *intended* to be Atari's new flagship home computer. Quote Link to comment Share on other sites More sharing options...
1050 Posted September 26, 2017 Share Posted September 26, 2017 The 1050 is built the same way though and it is a 'flagship' device. The issue was (I'm thinking) that cost of plastic OTP rom was too volatile for them to commit to any one design until the age of the XF551 came along for example where there is no jumper nonsense at all. Paranoia might have played a part too, once trapped into a mask rom design, the dirty bat rastard chip suppliers had them over a barrel and would only turn the screws then you see. So I'm looking at your single eprom 1200XL and thinking that with some deciphering of jumpers and whatnot one could use that extra socket to hold a BASIC eprom and have built in BASIC. Maybe there is nostalgia involved in using a cart though? Many other possibilities for those not going the route of installing heavy weight modern toys that negate to some extent the need for a spare OS socket in the first place. Still just fun to think on too. It's there and it's handy so what can we do with it? Quote Link to comment Share on other sites More sharing options...
ACML Posted September 26, 2017 Share Posted September 26, 2017 So there's a bunch of oddities in the 1200XL motherboard design that I wonder if we'll ever get to the bottom of. Isn't that the truth. Someone please tell me why Atari went through the expense of putting in a better video circuit then didn't connect the chroma line to the monitor jack? Why would anyone do this? Surely it cannot be an oversight. Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted September 26, 2017 Share Posted September 26, 2017 AFAIK, there are only two motherboard versions (and by versions I mean who made the board) I call them the light green and the darker green versions. There is TT for a patch for CPU timing issues (If I remember that correctly) which I just found a 1200XL that has it. I have personally have never seen EPROM or 28pin versions, nor the REV 11 OS - but there is a TT article on how to replace the EPROMS with ROM and also with the newer OS that supposedly fixes a reset timing issue. This is all from memory -- so I might be a bit off. 1 Quote Link to comment Share on other sites More sharing options...
Lord Thag Posted September 27, 2017 Share Posted September 27, 2017 Isn't that the truth. Someone please tell me why Atari went through the expense of putting in a better video circuit then didn't connect the chroma line to the monitor jack? Why would anyone do this? Surely it cannot be an oversight. I'd bet it was. Atari was legendary for one department not knowing what the other was doing. Remember when Kevin interviewed Arik Wilmunder about Star Raiders 2? He worked on it for months only for Atari to realize... 'oh. shit. we already released Star Raiders 2. Nevermind!' I'm not a hardware expert at all, but I'd guess all the design elements were relics from when the 1200xl was the Sweet 16 project. All those unreleased expansions and peripherals that never saw the light of day. Who knows? Quote Link to comment Share on other sites More sharing options...
Deteacher Posted September 28, 2017 Author Share Posted September 28, 2017 Ok, latest update: I received my new 6502 in the mail today (that was fast!) I popped it in and...same result. Still get the pink band across the screen with the cart in the slot, and a plain black screen with the cart out. I called Best Electronics back and he said that another chip is bad...somewhere. He's thinking it might be a bad RAM chip, but I'm still thinking it might be the Antic or the GTIA. He said my only option at this point is to keep swapping chips with known good ones. Unfortunately, I don't have anything compatible. Even if I did, I'd be hesitant to risk killing another machine for the sole purpose of testing chips. So, I could either keep buying chips, or try to find someone with more knowledge on this machine than me. Having said that: Is there anyone on here that would be willing to take a crack at this? I can send the motherboard to you (since it's already taken apart...and it would be cheaper to send just the board than the entire hulk of a machine.) I would pay for shipping both ways (from Newark, DE) and pay for your services. If you're willing, could you please PM me? Or, if anyone has any other suggestions of what I might be able to try, I'll take any and all help I can get. I do not want to just toss this. Quote Link to comment Share on other sites More sharing options...
Paul Westphal Posted September 28, 2017 Share Posted September 28, 2017 (edited) Deteacher, That's the first time I've seen a 1200XL with 28 pin EPROMS for the factory OS. Just curious, what's the serial number on your 1200XL. I am speculating that you might have a "very" early 1200XL for it to have EPROMs at U12 and U13. I could be way off. Maybe you or a previous owner tried a different OS, but then returned it to Rev 10 not wanting to reset the W6-9 jumper (reverts back to 24 pin ROMS). Look at the empty pads at W6. Looks like they are filled in at the factory. You might have a "very" early production 1200XL (i.e. the ROMs weren't available yet). If you need a new ANTIC and GTIA, another cheap alternative is to buy a cheap CPU board from a 400 or 800. The ANtIC and GTIA are the same as the one used in the 1200XL. The CPU might or might not be. If it (400/800 CPU board) has four smaller IC's, its the 6502B and won't be compatible, but if it only has one smaller IC (board CO15500), then it has the 6502C (SALLY) and that too is the same as the 1200XL. B&C sells the CO15500 CPU board for $20 and has the ANTIC, GTIA and SALLY that is compatible with the 1200XL. Oh crap, I let that secret out. those won't last long. I restored ONE 1200xl Mobo that had the XL O.S. sockets from the factory, and that one went to Joe Decuir for $20. It was the only one I saw out of the ten I restored. Edited September 28, 2017 by Paul Westphal Quote Link to comment Share on other sites More sharing options...
yorgle Posted September 28, 2017 Share Posted September 28, 2017 Or, if anyone has any other suggestions of what I might be able to try, I'll take any and all help I can get. I do not want to just toss this. I sent you a pm. If you're interested, I have an extra motherboard you could have for shipping cost. It booted the last time I had it in a 1200xl. 4 Quote Link to comment Share on other sites More sharing options...
Deteacher Posted September 28, 2017 Author Share Posted September 28, 2017 PM sent! YES, please! Quote Link to comment Share on other sites More sharing options...
Paul Westphal Posted September 30, 2017 Share Posted September 30, 2017 Score on that one! Quote Link to comment Share on other sites More sharing options...
Deteacher Posted October 10, 2017 Author Share Posted October 10, 2017 Update: Thanks to Yorgle's generosity, my 1200xl is alive and well again. I'm still going to work on repairing my bad motherboard. Would be great to have a spare on hand. One thing is for sure. I'm never going to use her for testing purposes again. Thanks to all for all the help and advice you've offered to me. I've learned a lot from this experience and I'm looking forward to tinkering around some more with my bad board. Still have some chips to swap out. I'll be placing an order with Best very soon. 3 Quote Link to comment Share on other sites More sharing options...
JGRAHAM2 Posted June 7, 2022 Share Posted June 7, 2022 On 10/10/2017 at 7:30 PM, Deteacher said:I'm looking forward to tinkering around some more with my bad board. Still have some chips to swap out. I'll be placing an order with Best very soon. Did you ever get the bad board fixed? Quote Link to comment Share on other sites More sharing options...
Deteacher Posted June 7, 2022 Author Share Posted June 7, 2022 No. I still have it. I have it stored away and planned on keeping it for spare parts. Fortunately, the need for parts has never come up (knock on wood.) 1 Quote Link to comment Share on other sites More sharing options...
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