Quote Originally Posted by afbecker
When tested apart, both boards run and test out perfectly.

When I connect the secondary to the power buses of the primary, the PIC on the secondary board fails to operate. I have checked the Vss and Vdd pins on the secondary and I get 5VDC on Both!
Sounds like a problem with the ground trace to the second board.

You say it works fine on its own, so is the terminal you are taking ground from on the first board somehow rising to +5v when the first board is running?

Regards