OpAmp onboard preamp problem

[MarcoMike]

hi, not really a stomp box, but I need some feedback on this:
I have this active bass that sometimes gets very quiet (the battery is ok...). not while working, but just every now and I connect the jack  and it does not give full output.
what i found out is that if I touch the input pad on the circuit (making the usual loud hum) everything goes ok, and after it works with no problem.

the input is just a voltage follower (non inverting, signal on +, output and - connected): PU->cap->Vr thru 100k res-> + input

I thought this could be an input bias issue... is that possible? how to solve it???

[ghostsauce]

I can't really answer any of your questions, but the first thing I would do is re-flow the solder in there. Years of use might have given way to bad joints. Beyond that, i'm sure you'll get some good insight here in a bit from the smart guys

[CurtisWCole]

Sounds like you have a grounding issue. Check that as well.

[MarcoMike]

thanks guys.
I'd exclude the cold joint. checked for that already (and re-soldered it already).

[Gurner]

Check the dc voltage on all pins and post the results here.