Let's say you own a 4001 or 4003 bass with standard (i.e. not modified) internal wiring and the two jack sockets - "Standard" (i.e. mono) and "Rick-o-Sound" (stereo) - and you want to know the actual measured values of your two volume pots. Thanks to the way the instrument is wired, you can do this without having to de-solder anything or even remove your pickguard!
This is what you do...
1. Find a STEREO (tip-ring-sleeve) jack plug and take its barrel off so you can easily access the solder tags.
2. Plug it into the Rick-o-Sound jack socket. Do not plug anything into the mono jack socket.
3. Get your DMM, set it to measure Ohms and clip its negative test lead to the "sleeve" (ground) tag of the jack plug.
4. Clip your positive test lead to the solder tag that corresponds to "tip".
5. Now for the crucial bit. Throw the pickup selector switch to the "Neck" position. By doing this you are disconnecting the treble pup from the circuit, thus leaving the treble volume pot unloaded.
5. Your DMM is now connected across the unloaded track of the Treble pup's volume control. It doesn't matter whether you have the pot turned up or down - that's irrelevant. Likewise, it makes no difference how you have your tone control set, because that's out of circuit too. Take your reading and note it down.
6. Now move your DMM positive lead to the "ring" tag of the jack plug and flip the pickup selector to the "Treble" position. You can now take a reading across the Neck volume pot.
Job done.
NOTE: If your bass is one of those with a single mono jack socket - the 4003s for example - this method won't work for you: you'll have to get inside and do a bit of de-soldering to disconnect the volume pots from each other before you can measure anything.
