760XD: TV-Out makes awful colours! (fixable?)

[CYBERYOGI =CO=Windler]

I have installed the open source monitor adjustment program Colorimetre HCFR with Spyder II colorimeter on my historical high end laptop IBM Thinkpad 760XD to examine and adjust CRT TV sets (e.g. a Saba Ultracolor fron 1978). Unfortunately I had to discover that the video output jack makes really awful colours (even worse than its TFT) those make many screen test modes useless.

I am aware that the 16 Bit colour output is not really true colour, but it is so off that this can't be the problem. Particularly the 3 highest blue steps in a blue scale look all the same, and with grey scale the medium brightnesses have a terrible hue; the brighter grey is way too violet while darker grey has a yellow tint. Only white and black and the 100% primary and secondary colours look ok.

- Is this a defect, or is the output chip really so bad?

I mean, is only my specimen faulty or is this a known bug? If yes, is there a software or hardware fix for this? E.g. in the C64 DTV (hardware C64 emulator in a joystick) there were severe colour flaws by wrong SMD resistor values. I have fixed mine by soldering correct values in. Is there a similar fix for the 760XD graphics card?