1200XL Green Screen

[flashjazzcat]

Anyone with electronics knowledge know where the first point of call would be when investigating a 1200XL with a persistently green screen? I'm referring to the schematics at the moment in an effort to try and trace the fault. The machine has had some kind of video mod performed on it, which I'm now attempting to inventory in order to identify the offending component. I've just PAL modded it, but this isn't the cause of the issue: even when the colour trim pot is rolled right back, the usual blue screen is bright green.

[russg]

Anyone with electronics knowledge know where the first point of call would be when investigating a 1200XL with a persistently green screen? I'm referring to the schematics at the moment in an effort to try and trace the fault. The machine has had some kind of video mod performed on it, which I'm now attempting to inventory in order to identify the offending component. I've just PAL modded it, but this isn't the cause of the issue: even when the colour trim pot is rolled right back, the usual blue screen is bright green.

With no cart, a 1200XL is supposed to boot to the rainbow ATARI screen. I know this doesn't help. You get a blue screen with a SpX cart. I guess what I'm asking is if a cart

loads and gives you a D1: (Sparta) with green screen or probably no cart screen, just plain green.

Edited March 28, 2014 by russg

[Rybags]

Might be an idea to do a simple colour-bar test, see if there's a hue shift that affects everything.

Does adjusting the trimmer do anything? Those things can play up.

[flashjazzcat]

With no cart, a 1200XL is supposed to boot to the rainbow ATARI screen. I know this doesn't help. You get a blue screen with a SpX cart. I guess what I'm asking is if a cart

loads and gives you a D1: (Sparta) with green screen or probably no cart screen, just plain green.

 

It's got a multi-OS board in it, so it just boots to the self-test. But you still see the default graphics 0 display for a short while during the boot process, and that's bright green.

 

Might be an idea to do a simple colour-bar test, see if there's a hue shift that affects everything.

Does adjusting the trimmer do anything? Those things can play up.

 

The trimmer doesn't significantly alter things until it reaches a cut-off point whereby the colour signal goes out of range and the display goes mono, which is exactly as I'd expect. What's odd is that the blue text in the Self-Test is indeed blue, while the default editor display is green. The colour appears to be massively overdriven, too, with heavy bleed, which I wouldn't expect from a ClearPic modded machine. I did ClearPic on two other 1200XLs and the (also PAL) Y/C is really excellent. Circuit appears identical on this one, so I'm suspecting something's busted elsewhere.

Edited March 28, 2014 by flashjazzcat

[Rybags]

One or more 3rd party OSes use green text screen but I suspect you'd know that... blue/green are adjacent hues, but default PF2 is hue 9, just checked and hue 7 is used for the Self Test menu text, it's comfortably in the middle of the range of hues that have blue as the dominant component.

 

Also... aren't wrong colours classic symptoms that the video circuit or even entire machine is receiving the wrong voltage?

Edited March 28, 2014 by Rybags

[flashjazzcat]

One or more 3rd party OSes use green text screen but I suspect you'd know that... blue/green are adjacent hues, but default PF2 is hue 9, just checked and hue 7 is used for the Self Test menu text, it's comfortably in the middle of the range of hues that have blue as the dominant component.

 

 

Fantastic Rybags: APE Warp OS was active and guess what colour it uses for the editor. D'Oh! Selected stock XL/XE OS and all is well. Video output still isn't perfect but I can easily make additional tweaks now.