Interesting phenomenon, can anyone explain this?

[soggybag]

I have a Les Paul Style guitar with three humbuckers and a three position switch. The switch activates the bridge pickup in one position, both the bridge and middle pickup in the center position. In the up position the switch activates the neck pick up alone. I'm not completely sure about the wiring but this how I think it is wired. Now for the phenomenon...

When go and Rock with the band I borrow an amp, it's a Jazz Chorus something, if I switch the guitar to the neck position the volume fades up and down and fades out. Later this pickup will work. The volume fades up and down, it's not like it's a bad switch where it cuts sharply. The fading is sort of erratic but not choppy.

At home if I plug in to the digital recorder this doesn't happen?

[Ibanezfoo]

I had something similar in a Les Paul clone and it was a bad volume pot... This was for the neck pickup.

[petemoore]

  Switches seem to hold up pretty good !
  The newer LP EPI has more workable wiring, not the teensy wire that was like working with cheese that the old one had.
  The pots 'worked', super sticky [required positioning my shoulder to get enough grip], and tapered such that the bypass caps I like didn't seem to make much difference, full-on sounds full on, then mud between about 8.5 down to where you notice a difference [oh yea, the guitar gets turned off a lot because the pots don't do much until right where they turn off suddenly.
  Now I have smooth turning knobs, frequency control between 8 and 10, volume control below that, much smoother spread of control, ''some'' improvement of the sudden final drop to 'off' near the CCW stop at about .8, I think that's the nature of the beast. Having at least a detectable slope change helps me to not shut the dern guitar completely off when searching for the volume drop that should have been made later in the chain.

[punkin]

Any chance it's the amp or the power source?

I had a similar thing WAAAY back. Some of the kids my son hangs with would come over. They'd bring some amps n stuff, plug in. One of the boys was borrowing my Univalve. Everyone else was working just fine but my Uni would cut out now and then. When I was advised of the technical problem I came down to check it out. Of course when I alone and was testing, trying to duplicate the problem, no trouble found but then again when the whole crew was at it, the Uni would cut out.

Turns out we were marginally taxing the power source. Split the gear up across two different AC breakers and all was fine.

Just a thought.

[soggybag]

Not sure about the power source. What's interesting is the other two switch positions work fine with no problems. Only when switching to the neck position does the problem appear. I always notice with this same amp. I haven't tested it with another amp. But it doesn't appear when I use the digital recorder. If I plug into that the neck pick up seems to work without the problem.

Another funny thing, is that after I have been playing a while the neck pick will start working normally. I started to think it could something about the current flowing through the two coils doing something weird until it reached some equilibrium.

[Lurco]

some leaky capacitor thing?