Received a box of faulty PCBs to repair from USA.I started my work on them with this Teenage Mutant Hero Turtles by Konami:
PCB was in very good state and played fine with correct sound too but it had a color issue, the screen was yellowish simptom that the BLUE color was missing:
BLUE, as well as RED and GREEN, is generated by a custom SIL marked ‘052535’ (basically an R2R resistor ladder which acts as DAC , see my reproduction post here for more details)
Probing the custom revealed activity on all inputs (pin 2-3-4-5-6-7 ) but output pin 8 was stuck low:
So the component was internally faulty.I replaced it with same part taken from a spare board :
This restored the missing color.End of job.