Hi Phillip,

A couple things come to mind -

First, use of a protoboard (compared to a pc board)provides more capacitive coupling between signals than you might like (the coupling gets worse the higher in frequency the signals go). You might try reducing the clock frequency by a factor of 2 to 4 and looking at the amplitude of noise on the power line. If it goes down, you might seeing the protoboard coupling affecting the power quality.

Second, provide some amount of capacitance between the power and ground pins of the 8031. Use a bypass capacitor to shunt high frequency noise on the power pin to power return before it reaches the 8031.

Have Fun,

Bruce