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800xl Red Screen. I want to fix!

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Hi everyone.

 

I recently picked up an 800xl that on the outside looks mint, but upon power up it displays a red screen and that's it.

 

So, reading on here and other forums around the net, the first culprit appeared to be the memory - a couple of chips were indeed almost too hot to touch, so I sourced and replaced all 8 ( 4264-15's ).

Now when the system is powered up the ram chips all run at a cool temp - way cooler than before. But, still the red screen. So I have scoured the forums trying to get some pointers as to what to try next.

 

If I leave the system running for a few minutes, the top right chip becomes hot - I beleive that is the BASIC ROM, it's marked C024947A-01. I also understand that sometimes the ANTIC and GTIA chips can also fail ( these being the chips tasked with correct display? ).

 

Has anyone had any success with tracking down the cause of the RED screen of Death and resurrected an 800xl successfully? If so, any pointers as to what fixed it? I am happy to work through this, report my findings to help others, and get this clean machine back operational again. If I wanted to source replacement chips here in Canada/US where would I start? Best Electronics?

 

Anyway, any advice would be appreciated.

 

Damian.

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Powering up and the screen staying static colour means the OS can't initilize and plenty of things could cause it from failed CPU to bad Rom or Ram or a failed Antic. Or it could be something as simple as one of the 7400 series logic chips that costs about a buck to replace.

 

An easy way to test if you don't have equipment like logic analyser is to swap in chips from the bad computer into a known good one at a time and see which ones don't work.

 

Main ones to test would be CPU, Antic, MMU, OS Rom, Ram chips.

Edited by Rybags
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You're replacing IC's and not installing sockets?

 

The main culprits in my experience are RAM, the CPU and the OS ROM. If the basic ROM is getting hot, it can be removed to see if it is the problem because it isn't necessary for operation.

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True the smartest thing you can do as you work on an Atari is to socket anything you replace. This helps in troubleshooting and chip replacement big time. tracking down bad traces or bad solder joints without risking burning up any other chips is a thing to behold.

 

I don't like the bent over transistor or the way the top of that crystal looks!

Edited by _The Doctor__
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Unsocketed board - makes it a whole bunch harder and more labour intensive. Don't desolder or attempt to solder sockets in unless you have the required skills.

If you don't have the skill, practice on something not valuable like an old PC card that uses the large DIP chips or a game cartridge you can live without.

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according to '800XL Field Service Manual' pg 3-1, a red/brown screen can be U2-U5, 18, 19, 28, 30. 'Isolate and replace defective IC'.

That doesn't help much, because you need to swap chips out to test them with a working motherboard.

www.atarimania.com has the SAM'S 800XL photofact book with schematics and parts (chips) names and locations.

I haven't had much luck swapping out chips and solving a problem, but it is the only way I know.

Oh, the SAM's has a TROUBLESHOOTING section with logic probe symptoms and oscilloscope waveform checks (not pictures of waveforms)

So for that you need a logic probe and oscilloscope. A VOM is a basic tool that could help some.

I see atarimania has a 1200XL field service manual that might help.

Your mb seems to be about all non-socketed. The MMU is socketed (the center top chip). For sure it would be good to

swap out your socketed chips. Your picture shows MT drams, so those would be before you replaced the RAMs, MT

are known bad.

Also, SAM's still sells the 800XL photofact book.

Edited by russg
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Hi Guys, thanks for the valuable input. I just replied to your comments but it didn't make it to the forum for some reason - so here goes again.

 

As soon as I soldered in the last of the memory chips, the thought occurred to me that I should have socketed them! Doh! You live and learn. I assumed ( incorrectly as it turns out ) that all the 800xl's had soldered IC's. I have a fully operational 800xl here also. I lifted the hood, and it does have ALL socketed IC's - see image. So, I have the option of using these known good IC's for testing I spose. Doesn't make me feel any better lol. Don't fancy my chances of removing a bunch of them without breaking something.

 

So, what would be the best way to go about this? If I can remove the IC's from the bad board without any damage to the chips, I can do this one at a time and add a socket then swap them over to see if it will bring the bad board back to life.

 

I suppose that would be the way to do it. If you had to chose an order of which chips to desolder first, what would be your best bet? lol. It would make sense to try and minimize the work/disruption/potential damage with this approach no?

 

I assume I can pick up sockets and any good electronics outlet?

 

 

It's getting late, been a long day. Need to sleep on this one.

 

Thanks again guys.

 

 

 

 

 

 

 

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The test procedure either way will work but it's probably easier to put a chip at a time from the bad board into the good one.

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and safer! I always test the chips one at a time from the bad unit being put into a good unit, it prevents killing good chips!

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Hi Guys, thanks for the valuable input. I just replied to your comments but it didn't make it to the forum for some reason - so here goes again.

 

As soon as I soldered in the last of the memory chips, the thought occurred to me that I should have socketed them! Doh! You live and learn. I assumed ( incorrectly as it turns out ) that all the 800xl's had soldered IC's. I have a fully operational 800xl here also. I lifted the hood, and it does have ALL socketed IC's - see image. So, I have the option of using these known good IC's for testing I spose. Doesn't make me feel any better lol. Don't fancy my chances of removing a bunch of them without breaking something.

 

So, what would be the best way to go about this? If I can remove the IC's from the bad board without any damage to the chips, I can do this one at a time and add a socket then swap them over to see if it will bring the bad board back to life.

 

I suppose that would be the way to do it. If you had to chose an order of which chips to desolder first, what would be your best bet? lol. It would make sense to try and minimize the work/disruption/potential damage with this approach no?

 

I assume I can pick up sockets and any good electronics outlet?

 

 

It's getting late, been a long day. Need to sleep on this one.

 

Thanks again guys.

 

 

 

 

 

 

 

From my experience, I haven't had good luck swapping chips. It would be better to just get another 800XL. You have a good mb, just use that.

I'm sorry, your new 800xl is nice and clean, but you can use your working mb and the new, clean keyboard and case with it.

Except you can swap the few socketed chips.

Edited by russg
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As soon as I soldered in the last of the memory chips, the thought occurred to me that I should have socketed them! Doh! You live and learn. I assumed ( incorrectly as it turns out ) that all the 800xl's had soldered IC's. I have a fully operational 800xl here also. I lifted the hood, and it does have ALL socketed IC's - see image. So, I have the option of using these known good IC's for testing I spose. Doesn't make me feel any better lol. Don't fancy my chances of removing a bunch of them without breaking something.

 

 

That's the Chelco mde version and it's the best kind to work with. Because it's usually fully socketed and it has gold plating on the PBI.

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Hi Guys,

 

Ok so firstly, thanks for all your input so far. As you can see from the image I have fitted sockets to the GTIA, ANTIC and CPU. I spoke with ( and I have forgotten his name ) the guy from Best Electronics who was super nice, and very knowledgeable the same as you guys. We thought we would start with the cpu and move on from there. I have all three of these socketed chips coming - should be about two weeks.

I will keep you all posted!

Of to grab a cold one now - even though it's -10c out. Cheers!!

 

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and safer! I always test the chips one at a time from the bad unit being put into a good unit, it prevents killing good chips!

Yes! Like the sound of that. Good common sense! Thanks.

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I don't get it - you ordered all of those chips without knowing which one is faulty?

 

You have a display (albeit red screen) which means GTIA at least can do that much.

If the screen is steady (non-rolling) then it means Antic is sending VSync commands and is at least partially functional.

 

Given you also have a good machine and the skills for solder/desolder it would have been an idea to do the one at a time testing.

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I always swap into a working board. It's _very_ rare that one chip takes out another unless the unit is left on for an extended period. If you have a working motherboard, just try them one at a time to verify which ones are good.

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I don't get it - you ordered all of those chips without knowing which one is faulty?

 

 

The chips themselves are pretty cheap and with minimum order sizes and shipping costs, why not? It's good to have spares. :)

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I don't get it - you ordered all of those chips without knowing which one is faulty?

 

You have a display (albeit red screen) which means GTIA at least can do that much.

If the screen is steady (non-rolling) then it means Antic is sending VSync commands and is at least partially functional.

 

Given you also have a good machine and the skills for solder/desolder it would have been an idea to do the one at a time testing.

I see your point, but at the end of the day I would like to get this machine up and running. So I will ultimately need more chips. There is a minumum order of $20. I think its a small price to pay to hopefully bring this mobo back from the dead. I am tempted to start swapping chips back and fourth, but I worry that I could do harm to the other working system. It's a possibility right?

 

FYI The display is steady red.

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The chips themselves are pretty cheap and with minimum order sizes and shipping costs, why not? It's good to have spares. :)

Yeah that's the way I see it.

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For the cost of mail ordering chips, I'd rather buy up used 600XLs. They all seem to be socketed and you get more parts for the $$$.

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Be careful when you try to plug in a chip that has been de-soldered from a board. There will be solder left on the pins, maybe a lot of solder. You don't want the old solder to contaminate the new socket or deform the connector.

 

Bob

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Be careful when you try to plug in a chip that has been de-soldered from a board.

Definitely true, but from the picture they look pretty clean. I often drag some braid down the pins to get the last of it off.
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Be careful when you try to plug in a chip that has been de-soldered from a board. There will be solder left on the pins, maybe a lot of solder. You don't want the old solder to contaminate the new socket or deform the connector.

 

Bob

 

 

Definitely true, but from the picture they look pretty clean. I often drag some braid down the pins to get the last of it off.

Yeah thanks that's good advice. I took my time desoldering the three chips. I used a solder sucker to remove all the solder from the pins on the underside of the board - very time consuming but in the end the chips basically fell away from the board. Cleaned up any stray solder left behind on the board surface with some solder braid and made sure that the pins were aligned before pushing them into the sockets. They went in easy and have a good firm fit. I checked for continuity from the chip pins, through the socket and into the board. They all check out perfect. So, just waiting for the replacement chips to arrive and what adventure that will bring.

 

Incidentally, anyone ever replaced a chip pin/leg? Cut one from a dead chip and soldered onto the 'stump' of a good chips missing leg? I wonder if that is possible.

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I've done that - I desoldered an Antic from an XEGS and made a meal of it. 11 legs broke off, got some donors off another chip and soldered them back on. Worked fine, not that I'd recommend it.

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Me too. If there's enough of the leg left, it can be done where you can barely tell. If the leg breaks off at the encapsulation, you have to try to get a thin wire soldered to the little bit of exposed metal, then tack it to the PCB or to a stiff wire in the socket.

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Me too. If there's enough of the leg left, it can be done where you can barely tell. If the leg breaks off at the encapsulation, you have to try to get a thin wire soldered to the little bit of exposed metal, then tack it to the PCB or to a stiff wire in the socket.

 

 

I've done that - I desoldered an Antic from an XEGS and made a meal of it. 11 legs broke off, got some donors off another chip and soldered them back on. Worked fine, not that I'd recommend it.

 

 

Yeah guys, this is what I will be tackling next....

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