wild circuit board has mind of its own

[MrDEB]

Have a PIC circuit that outputs a square wave that is upwards of 22khz.
It works but when I place a finger near the board it quits outputting.
The output of the PIC is connected to an LM386.
Have built same w/o any problems.
With project completely assembled, just placing hand near the enclosure causes it to shut off.
Thinking THERMIN PRINCIPLE?
Perhaps a bad decoupling cap as I have several on the board or perhaps 7805 output cap?
any suggestions.
Just picking up one end of assembled case causes it to shut off. YES I checked all connections. Just placing a finger over the board causes havoc.
Going to solder an additional cap on the supply rails.

 

[MrDEB]

Can one ground unused PIC pins?
If I touch the MCLR pin the output LED goes off. Touch most any unused PIC pin and I can make the LED go off or on.

 

[4pyros]

Are the unused pins looking for an input in your program? Can you post a drawing of what you have?

 

[MrDEB]

schematic and board

made two identical boards and only one acts weird
hope these are viewable?

 

[4pyros]

Is it posible you have a bad solder joint?

 

[Nigel Goodwin]

Can one ground unused PIC pins?
If I touch the MCLR pin the output LED goes off. Touch most any unused PIC pin and I can make the LED go off or on.

Have you left the MCLR pin floating?, this would cause your problem.

 

[MrDEB]

I will recheck the MCLR pin for solder connection.

 

[MrDEB]

THANKS Nigel, the solder between the pullup resistor (22K) and D2 (connected to MCLR) was at fault. Re thinking spraying a clear protecive finish to circuit boards after soldering. An ohm meter won't work with a clear protective finish (duh)
I reheated joint and connection was resolved.
Go have a beer and send me the bill--LOL