I have checked on resistors and diodes. They display proper values.
I tested for cold solder without finding any.
I have traced the voltage level on the transistors of the neckboard with a multimeter (attached is a picture of the measurement). It seems the problem is from the Transistor Q702 on the green line.
the transistor is operating but does output a lower voltage than what the one on the red line is doing. Is this component the source of the problem and have a weak behavior?
https://drive.google.com/file/d/17VT...ew?usp=sharing