Coco 1 and Coco 2 High Res video problem

[repetto74]

Hi guys,

 

I have both a PAL coco1 and a PAL coco2 the first being modded to composite and the second one using the RF output on a CTR monitor. Both will display a decent prompt screen (green and black). Today I received a CasDuino and tried to load some CAS images (Donkey King) but I have a weird result on screen for both. On the COCO 2 hooked to the RF output I do have a clear picture whenever the green and black display mode is shown but a scrambled picture with washed out colours when in High Res mode (pictures) as if the CRT Tv tuner goes out of sink when the high res video signal kicks in. On the COCO I through composite on a PC screen or the CRT TV I do have a stable picture but the colours are completely washed out with only a mix of blue and green on screen (this is barely unwatchable).

What can be wrong? Is there any tweak to be done to the color circuitry potentiometer?

Thanks

Edited April 5, 2018 by repetto74

[jhd]

I have never used PAL hardware myself, but I remember some discussion in the magazines that PAL systems cannot display artifact colours; the games just display in black and white. I suspect that may be (at least part of) your problem.

 

Can you get colours using the lower resolution graphics modes? Try quickly putting together something in BASIC to check.

[repetto74]

hi jhd,

 

yes in basic mode I can display any of the 8 available colours without any problem for both machines and as per the pictures colours are displayed as they should be at the prompt. What is weird is that the LCD screen is not really displaying a B&W pictures as you can see in pictures. It is more like a mix of faded blue and green with a lot of striped patterns. weird ...

[repetto74]

I have only check colours displayed in the main low res graphic mode. are there some more ? I am not very used to Tandy Coco programming.