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Deteacher

Did I Just Kill my 1200xl?

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Here's a pic of the back label:

 

attachicon.gifIMG_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)

 

post-30400-0-89884300-1506297736_thumb.jpg

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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)

 

attachicon.gifAssembly 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.

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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?

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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 by Deteacher

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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.

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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. :)

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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.

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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. :)

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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.

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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?

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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.

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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.

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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?

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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. :(

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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 by Paul Westphal

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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.

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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. :)

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