[Epiphone ES-339 Pro - volume controls]

Apologies, my previous post was wrong. It seems that you can alter the mix on the middle selector. As you roll off the neck volume pot it progressively reduces the neck pickup output but retains the bridge pickup output until you get down to around “1” or below, at which point it kills everything. The bridge volume pot acts similarly by cutting the bridge output and keeping the neck output.

[Epiphone ES-339 Pro - volume controls]

On 7/10/2018 at 2:34 PM, deeman said:

 

Ignore every post above. Here is the short answer :)

 

This is normal for your guitar. It is a function for how it is wired. You could go through all the trouble or cost re-wire it, but if you are on the middle selector and zero out the volume of one pickup, why not just switch to the pickup you want to use.

You cannot "zero out" the volume of one pickup on the middle selector. That is the OP's original point. Yes, obviously you could select neck or bridge if you only want to use one pickup, but the fact remains that on the middle position you cannot "mix" individual pickup volumes.