Re: Intermittent problem
Is it a double or single sided pcb? How much time does it stay malfunctioning? Try to freeze some portions of the circuit using a spray.
Some hints:
1- Resolder all components. Soldering points tend to degrade with age, even if you can´t see this (always happens in single sided boards, depending on age).
2- Older ceramic capacitors show intermittent shorts. Sometimes they work well when heated or resoldered but fail again after some time.
3- Resistors (mainly 1W or more) show intermittent failures.
4- In rare ocasions a bjt also fails intermittently.
5- xtal oscillators, diodes, zenners, etc also ....
Regards