if you have removed the tone control, both sides, and still have the problem then it is not your tone control causing the problem. if you have removed the ground off of the 5 way, and still have the problem, it is not that as well.
we know the circuit works, but the problem lies in the effects loop when engaged. we also know that when the effects loop is engaged, the send side is working. so we need to focus on the receive side of the effects loop.
i need to see some pictures of the wiring.
"Tone is in the instruments. Technique in the hands. Do what you will." ~quote from some guy at the TGP forum
"Without a doubt, the quality of your instrument will effect your tone, and any pickups, effects, amps, and microphones used along the way will also have an impact on the sound waves."~Cameron Mizell