CTM644 blue color gone

[Lastic]

I took the gamble on a cheap CTM644 that was tested on powering on but due to the seller not owning a CPC no video output was tested.

The brightness knob seems to be stripped or no longer connected to the internals.

When powering it on it display a yellow screen and when connected to either of my 2 CPCs it shows a black background with a dark-yellow font.

I am not an electronics engineer or an electrician but plan to open the case after leaving it disconnected for a few days to visually inspect if there are obvious broken/burned flaws.

I ran a basic listing in Mode 0 to display 8 color bars and clearly mine is missing blue.

Should I could my losses or might this still be repairable ?