Passive tone control malfunction - help needed please!?

I'm afraid that I'm a bit of a dunce where anything electrical is concerned, so I'm throwing myself on your (collective) mercy here .

I have just accquired a 1986 Westone Spectrum GT bass, which has two pickups (one "P" style and one "double J" style), a three-way selector switch, a master volume and front and rear passive tone controls.



Everything works as it should, except for the tone control for the rear pickup ...



When I roll off the treble, it acts exactly as a volume control and simply fades out the signal .

I guess that it's a problem with the capcitor or the pot, but I'm really not sure. Could it also be a problem with a short in the pickup windings (I seem to remember a similar issue with a Jazz Bass pickup that I had, which needed re-winding )?

Here's the wiring layout in the control cavitiy:



So, any advice please ?

 

Not entirely, Alcyon . You've just made me feel even more proud of my new (faulty) bass .

Thanks!

 

So, I took the rear cover off today and plugged the bass in to test out the function of the tone pot. I had a little poke around the wires to look for broken connections etc., but saw nothing odd.

To my surpise, it worked!

Then, when I flipped the bass back over to screw the cover on, a little blob of dried solder fell out . As I said, I'm a dunce with these things, but I assume that this solder blob must have been wedged in somewhere, causing a short on the tone pot . Does that sound likely?

Anyway, it's all OK now and I didn't even get my hands dirty!

Thanks a lot to evreyone who replied, or even just read my post and gave it some thought.