Tone knob and switch info

www.seymourduncan.com is a professional resource that offers diagrams of nearly every electric possibility (# of volume and tone knobs, switch types, and pickup types). There are others sites, but SD is the most complete.

What you describe sounds like pickups fighting against each other meaning, does this occur when using pickups individually or together? This is normal when using more than one pickup together, if it occurs in single mode, something is wired wrong. Another thing is, If using single, are you splitting coils? Individual coils wired wrong can do this, a bad pickup selector switch can also. A loose wire or fiber touching the tone pot capacitor or ground could also. A dead coil on a humbucker can as well. I'm guessing that you are using these in combo meaning a possible pickup selector switch may not be switching properly. The player's level of experience is also in my mind since, all of my guitars do the exact same ONLY when I use more than one pickup. I hardly ever use more than one at a time unless I'm playing a strat.

the knob closest to the neck is your volume. And the other two are tone. one is tone for bridge p/u & other is tone for Lead p/u. which is which can vary. you'll just have to listen. hope this helps

The one furthest from the switch is volume. The next one is a tone knob. Volume rasises or lowers the resistance and makes the guitar louder. You can also "clean up" a distorted tone by rolling off volume. Tone makes the sound more bassy or more treble.

Need more info: 1- does the volume control still change the level? 2-Does tone control still change the tone? 3- What happens when in the center position on pickup select switch? Put pickup switch in center position (both pickups active). Then take a coin and tap on the pickups. Does bridge pickup sound lower? Lastly remove rear electronics cover and inspect all wiring for something loose or disconnected.

chances are that the contacts in the pick up switch and or volume / tone controls have got dirty over time and are not making good contacts.
The 3 position toggle switches in most budget Les Paul copies are prone to failure - only making contact on one position as the springs get weaker - you could try unscrewing the back plate and examining what is happening in the switch.
Try rotating the volume and tone knobs vigourously to and fro - if this produces a crackling sound the contacts are dirty - further rotation will clean them a bit but a little squirt of switch cleaning spray will help too.
Other than that it could be dry solder joints anywhere on the back of the switches and knobs or poor contact inside the jack socket

NEVER use switch cleaner such as DeOxit on pots !!!!!

I have used CRC226 available at Home Depot electrical dept.

I SUSPECT that the resistance element in that pot is cracked. This is common if the knob sustained a hit. Replacing the pot is the only cure if the element is cracked.

Reviewing the schematic, ALL audio passes through the wiper on the HIGH tone pots. If the wiper is intermittent, so will be the sound.

If your unit is solid state amp, the pot looks like a 10K ohm LINEAR taper.
If you have a tube type, then the pot is a 250K ohm LINEAR.

Note that the other tone pots in the units are AUDIO tapers, but the high is a linear taper.

Get repair parts from either DigiKey.com or Mouser.com

The volume is a common problem ... Search for wiring diagrams for your guitar to find a better wiring. Or take it to a guitar repair centre to have it fixed.

To tell which pickups are selected with the switch if it doesn't have the little plate telling you, Turn one volume down and flick the switch one way so you can hear just one pickup.

Two ways of telling which one it is picking up ... A toppy tone is the one nearest the bridge ... a bassy tone is the neck pickup ... The middle selection on the switch is both coils selected ... If you cant tell by tone ... Tap the pick up and you'll soon hear which one you have selected.

The coil tap is the small toggle switch.

The controls should be setup in pairs (as long as the electronics haven't been modified. The two closest to the pickups are the volumes and the other two are the tone controls. The top knob set should be your neck pickup and the bottom set is for the bridge.

Schematics and wiring diagram for the typical les paul (sheraton) controls:
http://www.guitarelectronics.com/product/WDUHH3T2202

Good luck!