Crackle, intermittent sound when turning knob / Pot- Fixes and faults
If you turn the dial on your guitar amp and it crackles, sounds like old TV static or you lose sound or it jumps full volumen the chances are your pots may be worn or dirty.
Inside of a guitar pot (potentiometer) control
The picture to the left shows the inside of a very worn pot.
Silver inner ring – this is where the wiper connects to, its a rotating piece of metal and corresponds to the knob position.
Black outer horseshoe – this is where the magic happens, it’s a conductive track generally made from carbon and depending on the wiper position it will alter the resistance.
Points of interest.
You’ll see on this pot cleaning wasn’t an option as the track has been eroded away to the top left and right, this would cause big dips in volume and jumps, the only sure way to resolve this would be to change it.
What Causes crackles?
Oxidation and dirt builds up on the volume and tone controls (potentiometers or pots for short) carbon tracks. This can be caused by one of the below factors:
- Stored in damp/ dusty/ high temperature fluctuation conditions (Lofts / Garages)
- Pots which are used very frequently
- Pots which are rarely used
- Old amps with genuinely worn parts
- Contamination from beer, cider, other liquids
How to fix crackling pots
In the first instance we use a specially blended mix of a chemical called DeOxit. This is a blend of chemicals that clean the tracks and provide a protective conductive layer on the carbon track. Sometimes if the pot is slightly dirty this will do the trick first time and you’ll be ok for a few years before more dirt builds up. If on the other hand after the cleaner has dried there are either erratic volume changes or the crackles are still there we simply change the pot. It’s not worth the time in trying to clean the track or spray it any more.
Possible problems with cleaning volume controls
Often when people contact us they say they’ve tried to spray the pot but it’s not done anything. Quite often we find that they’ve sprayed the metal outside or not been able to get the nozzle right into the insides and the cleaner has been wasted. It’s quite hard to get the nozzle right in there as often the access slot is facing the PCB down. We’ve found the easiest way is to bend the plastic nozzle into a hook shape. This enables you to spray back towards you and hits all the vital insides! That is a workshop secret though! keep that between us!!!