Volume pot confusion

[tmoneygetpaid]

Hey,

A friend lent me his guitar, a reissue Fender Mustang, to replace the stripped out volume pot. I put a new alpha pot in (250k log taper), but somehow now the pot doesn't fully function-- it takes the volume down a litttttle bit, but doesn't go anywhere near silent when rolled down all the way. Oddly, when the tone control is removed from the circuit, the volume pot works perfectly. And when they are both in, the tone pot works perfectly.

When I removed the metal cover, there was a black wire that had broken. I investigated and it was the ground wire connected to the tin under the pickups. In the picture below, the 3 black wires you see soldered to the pot are the wire to the tin under the pickups at bottom, the wire from the switch, and a wire that goes through some routing to another spot in the body, presumably the bridge?

I wired according to the few pictures I found online, and have double, triple, and quadruple checked my wiring, and it seems right. Maybe I just need some fresh eyes to tell me where I've gone astray.

I'm driving myself nuts here. Any help is greatly appreciated. A picture of my wiring is attached.

[Justin Thomas]

Check the Fender website for a service diagram, first. Their wiring shows only TWO black wires on the back of the pot, plus the pot tab. Also - I&vedone this before - larger-bodied pots will not fit properly in the control cavity. The routings are not perfect reissues of the originals. You may be getting a partial short when the control plate is mounted. Try a smaller body pot or tape/insulate the Alpha. Good luck!

Justin

[big_teee]

Your ground wire is missing from the sleeve of the jack, to the back of the volume pot.
When you roll the vol. pot off it makes it quiet by grounding the output lead on the center of the pot!

[52 Bill]

Your ground wire is missing from the sleeve of the jack, to the back of the volume pot.
When you roll the vol. pot off it makes it quiet by grounding the output lead on the center of the pot!

The jack should be grounded by the metal plate that it is mounted to, but big teee points to a possible problem. If the new volume pot is not making a good ground connection to the metal plate the pot will not work correctly.

Make sure that the case of the new pot is reading zero ohms to the metal mounting plate and make certain that the CCW lug of the pot is reading zero ohms to the metal plate as well.

[big_teee]

Never count on foil to be the main ground.
It is only a shield, IMO.
Hard wire from the jack to the Vol. pot, and tie the two pot backs together with another ground wire.
T

[olddawg]

Never count on foil to be the main ground.
It is only a shield, IMO.
Hard wire from the jack to the Vol. pot, and tie the two pot backs together with another ground wire.
T

+1 Solder braid works great for this.

[g1]

I think this one is metal plate, not foil, but I get your point! Pot cases should be at least wired to plate, if not to jack.

[Mark Hammer]

Yep, the picture itself, suggests everything is going where it ought to...in terms of the wiring.

The only suspects here would be a) a solder joint that looks right, but is actually a cold joint making poor contact, and/or b) an "implied" ground connection, through the pot/jack chassis and pickguard that is not making the sort of connection you think.

The sensible thing to do here is run a wire from the ground lug of the jack, to the back of the tone pot and then to the back of the volume pot. My guess is that you'll be right as rain after that.