Jitter in a simple circuit

[joseph nicholas]

Hi, all, I am repairing a simple micro controller circuit that has a few 12 volt relays, a step down transformer, a smd voltage regulator, a bridge rectifier  using 4 diodes a smoothing capacitor and some passives.  The circuit does not function at all and after testing voltages I get a stable  5 volts out from the voltage regulator to the pic.  The problem is:  the voltages in the circuit jump a few milli volts.  When I looked at it using a DSO it seemed to be jittering on an off.   I think it is the micro controller causing the problem but before I give up I want an opinion.  Any assistance would be appreciated.