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It was definitely faulty TC2. I played with this spectrum for few days now and issue never come back. Installed heatsink on ULA anyway and replaced 7505 voltage regulator with TSR 1-2450 to reduce heat and prolong its lifespan :)

Think I fixed it by replacing TC2 with 15 pF capacitor. Will test it a bit more, but had 2h game session without the issues.

Nope, need to be metal. Also though it might be dry joint, so I de-soldered 1889, installed socket and put new 1889. Problem remains Yeah, I think I will purchase and swap ULA just to verify if it is source of that issue.

Yup, it reset to normal when it cools. You're right it is not 1889 i replaced it with new one. ULA getting really hot. One strange thing I noticed. Anytime I touch pin 13 of 1889 (chroma sub-carier) with multimeter probe, colors shows correctly and they stay correct as long as I keep touching...

Ok, bit more try & error with no joy. Replaced C65 again (trayed both 22uF and 100uF). Removed socketed and replaced LM1889 ... still same result. Maybe 4.xxx crystal ? On start: After 10 - 15 minutes:

Hey, thx for answer. PAL, already using composite video 12V on 1889 (pins 14,15,16) reads 11.55V. On upper ram 12.02V Cause I have no oscilloscope I set VR1 & VR2 to approximately get 50mV on pin 4 and -50mV on pin 2 relative to pin 3 of 1889 Overall image and color quality is quite good...

Hey, I am new here so ... hello everyone :) I have little problem with my speccy Issue 2. I can adjust colors using VR1 & VR2 and things looks good until ULA warms up (I mean turn hot). Then video loose color (goes monochrome). I can adjust color again using VR's but then, next time I start...