Sick 1200XL

[russg]

Cranked up 1200XL. It shows a ragged left and right borders. When the attract mode comes up, it has straight borders and

the bad borders as it cycles. What changes when it does the attract?

Also, it doesn't play Pacman right. It runs through ghosts without dying and it dies when there is no ghost. ie. the display

isn't in sync with the collisions.

I tried swapping Antic and GTIA.

Well, I played chess. It had wavy display. Then the video went out altogether, black screen. It still plays Pacman, I can

move the joystick and hear the gobbling of dots and sound of a death, just no video. So, no bad CPU, or it wouldn't be able

to play.

Pokey is sound, PIA is disk access, which it does OK.

Edited July 14, 2014 by russg

[russg]

Cranked up 1200XL. It shows a ragged left and right borders. When the attract mode comes up, it has straight borders and

the bad borders as it cycles. What changes when it does the attract?

Also, it doesn't play Pacman right. It runs through ghosts without dying and it dies when there is no ghost. ie. the display

isn't in sync with the collisions.

I tried swapping Antic and GTIA.

Well, I played chess. It had wavy display. Then the video went out altogether, black screen. It still plays Pacman, I can

move the joystick and hear the gobbling of dots and sound of a death, just no video. So, no bad CPU, or it wouldn't be able

to play.

Pokey is sound, PIA is disk access, which it does OK.

Also, RF works fine. That is the display works fine. It still messes up with Pacman cart, doesn't detect ghost contact, does death in open space.

Edited July 14, 2014 by russg

[Synthpopalooza]

Could be a bad GTIA ... I know one of the functions of the GTIA is handling PMG's and collisions.

[russg]

Could be a bad GTIA ... I know one of the functions of the GTIA is handling PMG's and collisions.

I'll try that again. The 1200XL is a bit complicated to open up and swap chips.

[+bob1200xl]

A stock 1200XL has bad composite video. On some monitors, the edge of the screen is skewed to the right for the first 10 or 20 visible scans, depending on the LUMA level or some such. The only way to fix it is to change parts on the motherboard - requiring soldering. I replace C115 and L15 with 1 ohm resistors to fix the video and R63 with a 1 ohm resistor to restore +5v on SIO. I use resistors because I think they look better - you can use wire.

 

The Pacman thing just sounds broken.

 

Bob

[russg]

A stock 1200XL has bad composite video. On some monitors, the edge of the screen is skewed to the right for the first 10 or 20 visible scans, depending on the LUMA level or some such. The only way to fix it is to change parts on the motherboard - requiring soldering. I replace C115 and L15 with 1 ohm resistors to fix the video and R63 with a 1 ohm resistor to restore +5v on SIO. I use resistors because I think they look better - you can use wire.

 

The Pacman thing just sounds broken.

 

Bob

Yes, that Pacman thing was because of a defective GTIA I accidentally put in that lacks collisions.

I'm having trouble finding C115, L15 and R63. I guess the C115 is a small cap, not the larger type. Can you tell me where to find these?

I have some 3 ohm resistors. Would a wire be better? Or, I can go get some 1 ohm.

Edited July 15, 2014 by russg

[+bob1200xl]

L15 is the green inductor just to the left of the white arrow. C115 is just to the left of L15 - large grey capacitor. R63 is just to the right of the other white arrow.

 

Bob

 

[+bob1200xl]

3 ohms will be fine for L15 and C115. Probably OK for R63, depending on the load on the SIO. Use 3 ohms, but get a 1 ohm for R63 when you think of it. If something draws 200ma on SIO (it shouldn't, but guys do things they shouldn't), you will drop .6v, which is a lot, although it may still run OK.

 

Up to you.

 

Bob

[russg]

3 ohms will be fine for L15 and C115. Probably OK for R63, depending on the load on the SIO. Use 3 ohms, but get a 1 ohm for R63 when you think of it. If something draws 200ma on SIO (it shouldn't, but guys do things they shouldn't), you will drop .6v, which is a lot, although it may still run OK.

 

Up to you.

 

Bob

FIXED! Thanks Bob. I used three 3 ohm. The R63 was 100 ohms, so I think 3 is headed in the right direction. Screen borders are nice and straight, Composite video as perfect as RF.

I went to two Radio Shack, no 1 ohms. I went to my electronics surplus but they were already closed.