Guitar Wiring fault diagnosis

earwighoney

Before I take the guitar to the repair shop, I've been having some problems with the wiring of my guitar. 

Before it would cut out if I touched the neck volume, but it seems to cut out when I touch the scratchplate. 

Is it clear from the pictures what the fault is? 

FTR the top right hand pot is the bridge volume. 





Thanks for looking. 

Funkfingers

The flat bottom pot casings in your photograph put up less resistance to impact damage than the type with the shaft showing through the baseplate in a dimple. 

Downward pressure on the pot shaft can be enough to distort the bottom of the casing. This, in turn, reduces the firmness of physical contact between the resistance track and the wiper contacts. Even pressing a control knob onto the shaft too firmly can be enough to distort the casing. 



Another possibility is that, in the tangle of wires tucked under the pickguard, something is intermittently touching something else that it should not, causing a short to ground and killing the signal. 

earwighoney

Funkfingers said:

The flat bottom pot casings in your photograph put up less resistance to impact damage than the type with the shaft showing through the baseplate in a dimple. 

Downward pressure on the pot shaft can be enough to distort the bottom of the casing. This, in turn, reduces the firmness of physical contact between the resistance track and the wiper contacts. Even pressing a control knob onto the shaft too firmly can be enough to distort the casing. 



Another possibility is that, in the tangle of wires tucked under the pickguard, something is intermittently touching something else that it should not, causing a short to ground and killing the signal. 

Thanks for the reply.  

I think I understand the last paragraph, but the first two are completely over my head!  

ICBM

When it does dead, does it go to complete silence, or is there still buzz or other background noise?

If it goes to complete silence it's a short - something touching where it shouldn't be, or possibly a faulty jack - and if there's residual noise it's an open circuit.

Does it affect both pickups or just the neck? If both, it's something between the switch and the jack. If just the neck, between the pickup and the switch.

The most obvious fault is that there's inadequate grounding - using the shielding foil to make the ground connections between the pots is prone to causing trouble. Solder a wire between all the pot casings.

earwighoney

ICBM said:

When it does dead, does it go to complete silence, or is there still buzz or other background noise?

If it goes to complete silence it's a short - something touching where it shouldn't be, or possibly a faulty jack - and if there's residual noise it's an open circuit.

Does it affect both pickups or just the neck? If both, it's something between the switch and the jack. If just the neck, between the pickup and the switch.

The most obvious fault is that there's inadequate grounding - using the shielding foil to make the ground connections between the pots is prone to causing trouble. Solder a wire between all the pot casings.

Thanks for the reply. 

It goes to complete silence, so I presume it's something between the switch and the jack then? 

I'll have a look at the grounding wire tomorrow. 

earwighoney

ICBM said:

When it does dead, does it go to complete silence, or is there still buzz or other background noise?

If it goes to complete silence it's a short - something touching where it shouldn't be, or possibly a faulty jack - and if there's residual noise it's an open circuit.

Does it affect both pickups or just the neck? If both, it's something between the switch and the jack. If just the neck, between the pickup and the switch.

The most obvious fault is that there's inadequate grounding - using the shielding foil to make the ground connections between the pots is prone to causing trouble. Solder a wire between all the pot casings.

Followed your instructions and it works!  

When I took the scratchplate off, it seemed also some of the solder joints for the selector switch had come off, and the grounding wire had come off the pot.  I resoldered them all and made sure all wiring wasn't touching the scratchplate and it seems to working well for now. 

The guitar's a Squier Joe Trohmann, so a Tele Deluxe and they are a real PITA in taking off so many screws etc.  Sure there are worse guitars though! 

Thanks again @ICBM! ;