XEGS chip compatibility

[Almost Rice]

Hi all. I was playing around with my broken XEGS. I bought it this way so I dont know what happened to it. It was the donor for my 64k 600xl. It would only give me a black screen.

 

I knew it was not the RAM, so I decided to find out why it did not work. First, I socketed the ram. They were empty so it was easy. Then I decided to socket all the 40pin chips.(This was to facilitate in the troubleshooting since desoldering 40pins takes me a little over an hour ) The 6502C and Antic were already socketed . I just had to do the Pokey, Freddie, PIA CO14795, and GTIA. I did not socket the ROM since I did not have a 28pin socket handy and no replacement ROM either.

 

Once done, I cracked open my 600xl(all chips were socketed). I suspected the PIA was bad. I took it from the 600xl and put it in the XEGS. It started right up but it immediately went in ROM/RAM check screen. This was because I had put the 16k chips from the 600xl into the sockets. Once replaced with the 64k chips, Missile command started right up.

 

I tried to play MC, but there was no sound and no enemy or their missiles. It might have been the ROMs so I put in a MC cart. Result was the same. Pacman was OK but no sound. I could not go into BASIC. I just get a blue screen. Same when keyboard is connected(so it properly detected the keyboard). I could not get into the diagnostic screen.

 

Next, I replace the POKEY with one from the 600xl. There was no change.

 

 

SO, thats where I am at. My questions are: Are the PIA chips fully interchangeable between the XL and XEGS ? Could it be the ROM ? (I dont have another XEGS so will the XL/XE roms work in its place ?) What could it be if the PIA is compatible? Anybody have a dead XEGS FS?(Nightsprinter ) I might go back and recheck my solder points.

 

I did not think anything was wrong with the POKEY since there was no change. I also did not test the SIO.

 

BTW Happy New Year everyone.

Edited January 1, 2006 by Almost Rice

[+Mitch]

They chips should be fully compatible between them, did you try swapping out the 6502, GTIA and Antic chips? I would guess that the 6502 is the most likely culprit.

 

Mitch

[Almost Rice]

I will try the other chips tomorrow. I am kinda sleepy right now.

[jaybird3rd]

I had an XEGS with a bad ANTIC chip once, so I swapped it out with one from a dead 600XL. It worked fine, and I suspect that the 6502 and the other coprocessors are also interchangeable.

[Almost Rice]

I had an XEGS with a bad ANTIC chip once, so I swapped it out with one from a dead 600XL.  It worked fine, and I suspect that the 6502 and the other coprocessors are also interchangeable.

992060[/snapback]

 

 

I change GTIA, 6502C, Antic, and Pokey. There is no effect. Also checked every solder point I put in for the Sockets.

 

The major problem is no Sound and wierd unpredictable gameplay. Some times PM collisions are not detected. Mostly the normal enemy logic is not there. I got the system into the Self Test. The mem test came out ok. The is still no sound. The keyboard presses are not detected, but the Start, Select, Option, and Reset keys are detected. Still cant get Basic or Basic XE to work.

 

I dont really know what else to do. The Pokey was replaced and all its solder points were tested. The only thing I can think of is maybe some connection to the Pokey was damaged. This similar to the damage I did to a 800xl when I connected 9v AC to the SIO port(dont ask). The pokey was damaged in that system, but I could still use it for sound.

 

 

Also tested the Pokey in the 600xl works fine. The PIA from the XEGS made the system go blank.

Edited January 1, 2006 by Almost Rice