Only get a yellow screen on my 800

[Gunstar]

My 800 arrived today, but While it does power up (I'm using my 1050 power-pack, that reportedly, from various sources, works with the 400/800, 810,150, etc.), I only get a yellow screen. I took it apart and cleaned it all out, and I made sure all the chips on the motherboard, CPU board and OS 10k rom-pack board were all seated correctly. some of them did push in some, so I'd hoped that it was just a case of a chip somewhere not being seated correctly. But I put it all back together and I get the same result; just a yellow screen. This is the first time I've ever owned the 800 model, so I'm not familiar with various symptoms with it. Is this similiar to the "red" screen people get on Xl/XE's? Any 800 experts that have encpuntered the yellow screen before and know what it might be? Everything *appears* to be in good condition on all the PCB's, but of course I'm hoping to avoid going through it all and testing every resister and capacitor, diode, etc. I'd just as soon want it to be a known problem with one of the chips, so I can just pop out the old and pop in a new, since they are all socketed. Thanks in advance for any ideas. Cosmetically, this puppy is in fantastic shape, after a good cleaning of the case, it looks new! No yellowing of the case at all!

[Gunstar]

OK, how about this; does anyone know or know of a site, that has the chip numbers listed for the various chips like Pokey, Antic, OS rom, etc., etc. both my 1200XL and 800 are all socketed chips, so I figured I could start swapping chips to see if I can locate a bad one, but (I haven't looked yet) not all chips have the same numbers, and I'd like to know what chips I'm swapping anyway. Thanks for any help in advance.

 

Well, so far I forged ahead on my own with swapping out chips and then checking it out on the 1200XL that I know works, so far, I've swapped out 3 of the 5 main chips and the 1200xl still worked fine, so I've just left the chips swapped. I'm down to two last main chips, one of which I know is the 6502, since on the 800 it is marked P6502B, but on the 1200 neither remaining chip has a 6502 designation, nor do any of the numbers match up, due to either different manufacturer or possibly just later/earlier chip models with completely different numbers, so I'm halting there for now. I still would have to swap out 74sXXX series gate chips, etc, some of which match up, some don't, but I also have a lot of 74 chips on hand anyway. After that, I guess it's onto the OS chips, unfortuantely this is pretty much were any cross chip compatibility may end, as the 800 has 3 main OS chips and the 1200 has 2. Not too mention different version OS's anyway. If it's not one of the last two main chips or 74 chips, etc., it may be something I have to look for on the small components, which is the part I'll really dread as it means taking the old multimeter and testing every diode, tranister, capaciter, resister, etc, as they all *appear* to be ok by looking at them, no obvious burnout... I'd still appreciate any possible help,

 

I hope it's not a OS or ram problem, I've tested it with my 16k ram expansion and the aftermarket 32k ram expansion in the 800, with the same result or lack thereof, so if it is a ram problem, then all the ram is bad, which I think unlikely. I'll keep forging on, hoping for any possible help from people here...

 

I have at least accomplished something out of all this today; since I had the two computers in pieces anyway, I went ahead and added the needed chroma line into the 1200xl so I at least have S-video output on it now, though it is quite inferior to the Xe's s-video, but still a lot better than standard composite. I may do a mocification sometime in the future to improve this, but for now it is o.k. I also properly grounded the SIO port pins 4&6 that Atari seemed to have overlooked, though I hadn't as of yet noticed any problems, I figured what the heck, better safe than sorry. and I also bypassed the R63 resister giving the proper power to the 1200 SIO so my P: R: Connection, Supra printer interface and midimate devices that all require power from the SIO will now work porperly on the 1200XL too.

Edited June 3, 2005 by Gunstar

[Callipygous]

I hope it's not a OS or ram problem

 

Well, I hate to tell you, but thats usually what causes a green or yellow screen. The ram is normally easy to diagnose. Just boot with one card at a time. If none work, then its highly unlikely all are bad as you say. The OS is 3 chips IIRC.

[Gunstar]

I hope it's not a OS or ram problem

 

Well, I hate to tell you, but thats usually what causes a green or yellow screen. The ram is normally easy to diagnose. Just boot with one card at a time. If none work, then its highly unlikely all are bad as you say. The OS is 3 chips IIRC.

866779[/snapback]

Yeah, it's a green/yellow screen depending on exactly how the tint is adjusted, so it's probably what you are talking about, I think I'll probably just see about picking up another OS pack, as I really don't think it is the ram or anything else after the swapping of chips and brief checking of all the PCBs. hOpefully B&C or BEST E has them for an inexpensive price. I will look at the OS board closer though, and at least test the components on it. Thanks for the heads-up though, on the green/yellow screen usually being the OS or RAM, that's mainly what I was looking for from someone.

[Xebec's Demise]

I had this problem one time. But I knew what caused it. It resulted from my brother spilling a soda into the Atari 800 keyboard.

 

I took the whole computer apart and cleaned it all off with a damp rag, but it still did not work.

 

The next thing I did is going to sound crazy, but it worked. I took my disassembled Atari 800 into the shower with me and completely washed out all the components, spraying warm water into every crevice and under and around every chip. Water does not normally damage electronics as long as they are powered off.

 

It is important to make sure the computer is fully dry before turning it on, so not only did I blow dry the computer off, but I let it sit out for several days to dry off.

 

I put it back together and it worked!

 

Notice any stickyness or spills inside?

Edited June 3, 2005 by Xebec's Demise

[Gunstar]

No, it's aas clean inside as if it had come off the assembly line yesterday. After Callipygous said he was pretty sure it was the ram or os, I carefully examined the OS board, and I found one of the chips had several pins bent under it and so it was not properly plugged into the socket. So, I took it out and carefully straightend the pins and re-inserted it. Hoping this was the cause of my problem, I tested the 800 again, but I still get the yellow/green screen, BUT, I figure the only way those pins could have been bent under was from someone removing them and bending the pins upon reinsertion, so, now, I think it might be a possibility (taken into account the obviously ameturish tamptering) that the rom chips have been inserted into the incorrect sockets and I'm now in need of a schematic or picture of the 800 10K ram board to see if this is the case. I hope so.

[Bryan]

You cannot swap CPUs between the 2 systems. The CPU in the 800 is a standard off-the-shelf 6502. The CPU in the 1200XL is the custom C014806 "Sally" chip, which has extra bus management features that eliminated a few IC's used in the 400/800.

 

-Bry

[Gunstar]

You cannot swap CPUs between the 2 systems. The CPU in the 800 is a standard off-the-shelf 6502. The CPU in the 1200XL is the custom C014806 "Sally" chip, which has extra bus management features that eliminated a few IC's used in the 400/800.

 

     -Bry

866870[/snapback]

 

I guess it's a good thing I didn't then, aye?

 

I really don't think it's the CPU though anyway, but I'm still puzzled as to whether it may or may not be the Rom chips, since I found the "F" chip in disarray, but after straightening it out, it still did no good. It could be that chip still, or it may be something entirely else, since straightening it out and plugging it in correctly changed nothing. I'm going to replace the roms anyway, and if that's not the problem, then I guess I have back-ups. But I'm still inclined now to think they are the problem since they have been the only thing I've found in the whole computer that was NOT "perfect."

Edited June 3, 2005 by Gunstar

[Callipygous]

BUT, I figure the only way those pins could have been bent under was from someone removing them and bending the pins upon reinsertion, so, now, I think it might be a possibility (taken into account the obviously ameturish tamptering) that the rom chips have been inserted into the incorrect sockets and I'm now in need of a schematic or picture of the 800 10K ram board to see if this is the case. I hope so.

 

Heh, most likely they took the good chips out of your machine to put in another 800. and then they shoved the bad ones in carelessly.

 

 

Anyway, the chips from bottom of the board (closest to the connector) are CO14599, CO12499 and CO12399.

 

HTH

[Gunstar]

BUT, I figure the only way those pins could have been bent under was from someone removing them and bending the pins upon reinsertion, so, now, I think it might be a possibility (taken into account the obviously ameturish tamptering) that the rom chips have been inserted into the incorrect sockets and I'm now in need of a schematic or picture of the 800 10K ram board to see if this is the case. I hope so.

 

Heh, most likely they took the good chips out of your machine to put in another 800. and then they shoved the bad ones in carelessly.

 

 

Anyway, the chips from bottom of the board (closest to the connector) are CO14599, CO12499 and CO12399.

 

HTH

866934[/snapback]

Thanks, I found a pic with captions indicating the "F" and "E" chips the 14599 and 12499, though they didn't mention the 12399 in caption. Anyway, I found the 14599 and 12499 on e-bay for 99 cents, assuming I win the auction, but I think I will as I don't think they're a hot item right now. Though they are being sold as-is , could be I'll get some more bad ones, but I'm taking the chance. The person is selling a bunch of chips, so I don't think they are necessarily just trying to pawn off a couple chips they know to be bad, but you never know. I'm ahead of the curve right now anyway; I got the 800, an 810 (that's working), a 410 (working), cables and Power supplies and like 5 cartridges and a pair of 5200 controllers in this lot, all for $10 plus shipping. I knew there was a possibility of a problem with the 800, but I figured it was worth it for that price anyway. I'm also 'watching" another 800 for $10 that's being sold as-is, to use for parts and/or backup parts. I'll make a working one out of the two if I get the other one. In the meantime, I'll just work on my memory upgrades for my 1040st and 1200xl. I'll come back to the 800 when I get some more parts.

Edited June 3, 2005 by Gunstar

[Gunstar]

Just a little update on my 800 situation. I got the old girl working. Turns out it was an old CTIA chip that was bad. I swapped it out with the GTIA chip of my 1200XL. I would have wanted to upgrade to a GTIA chip anyway, si this kills two birds with one stone. I did replace the ROM chips too, since one of the others was at least questionable, but I tested the new roms before I changed out the CTIA chip, so I don't know it the old roms are truely bad or not. So, anyone who gets a yello/green screen at start up, it just may be your CTIA/GTIA chip that is the culpret. It just figures that it was one of the last two dhips I didn't swap out before, since they were unkown's to me as the chips had different numbers due to being revisions/custom chips. Once I got a comprehensive list of all the 800/XL/XE IC's and their numbers, it was easy enough.

Edited June 11, 2005 by Gunstar

[Gunstar]

I do have another problem now. The 800's cartridge door won't stay closed, it looks as if the top-center of it has warped up so the latch can't get a hold on it due to the door pulling upward from the warp. It wasn't like this when I first got it, it seems to have warped while I had it off and laying aside?!? Any known fixes for this type of thing? Will just weighing it down with something reverse the warp if left for a while? Maybe there's a safe way to heat up the plastic enough to make it flexible enough to bend and form a new memory?

Edited June 11, 2005 by Gunstar

[Xebec's Demise]

Did you ever try some AR timing on the 800? Still curious.

[Gunstar]

Did you ever try some AR timing on the 800?  Still curious.

880515[/snapback]

not yet, but I will.