Wrong colors.

Symptom: Wrong colors.
Target : C-64 (all models)


Possible sources of failure
  - transistor Q4/Q3
  - modulator
  
Analysis
Transistor Q4/Q3 ok?
 
  Replace transistor Q4 (or Q3 on new boards) with a BC 547.
 
Modulator?
 
  Replace modulator completely. Alternatively, replace all
  transistors except for the HF transistor (max. 3pcs).