DYING TONE POT?

[rayc]

I recorded something with my bass today. It's a 41 year old bass and has had the input jack replaced about eight years ago. Apart from that it's "all original".
I noticed a buzz signal when using it.
I've experimented with it and there's a signal just a hair under 2Khz when the tone pot is turned UP or any where along it's path. NO, buzz when the tone pot is rolled all the way DOWN.
I opened the control cavity and things jump about if I touch a screw driver to the solders on the pot. .
It's a Vantage VS695B with a single split pick up.

The pot does have a little resistor, (?), attached.
I THINK the pot says M250kohms & 12k
The solders appear solid all around the place.
photographs:

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Diagnosis? Prognosis? Hypnosis?

[CeeBee]

That is a capacitor across the pot. If anything goes belly up it is probably the capacitor. Touching the solder with a screwdriver will change the capacitance of the circuit and cause the signal to jump around. See if you can find the value, (probably 0,047 microfarad) and change it and see what happens.

[muttley]

The capacitor would be the first thing to check. After that the wipers in the pot can tarnish and become erratic although that is unusual unless it has sat in one position for a while in cold or damp. If it were a dry or failing solder joint you would tend to get more a immediate drop in an out of the signal.

[Greg_L]

It's possible but very unlikely it's the cap. Those types of caps don't usually just wear out, especially since it sees no significant voltage or current whatsoever. But maybe. Instead of a screwdriver, use something non-conductive like a wood chopstick to poke around. Touch solder connections and jiggle wires around and see if the noise reacts.

[muttley]

It's possible but very unlikely it's the cap. Those types of caps don't usually just wear out, especially since it sees no significant voltage or current whatsoever. But maybe. Instead of a screwdriver, use something non-conductive like a wood chopstick to poke around. Touch solder connections and jiggle wires around and see if the noise reacts.

Yeh, it's uncommon for them to fail but they do rarely. Same with the pots but they do on occasion too. Mostly through standing idle too long or from people who tinker and don't know what they are doing.

From Rays description it does sound like something is bleeding away randomly which steers me away from the soldering. You are correct though. Have a good wiggle about and see if you can detect any extraneous noise or such like. Troubleshooting these things remotely is tricky.

[muttley]

I am assuming you have checked ground continuity?

[rayc]

Sorry for the delay...I'm waiting for a Multimeter to arrive given that visual appraisal isn't enough.
I'll get back with an audio sample and the results of chop sticking, wiggling and continuity testing when I have the device.