No dije de limpiarlos por fuera
Eso sería solamente estético 
https://www.forosdeelectronica.com/...=FORID:10&ie=ISO-8859-1&q=potenciometro+sucio
https://www.forosdeelectronica.com/...=http://www.forosdeelectronica.com/usercp.php
https://www.forosdeelectronica.com/...%2F%2Fwww.forosdeelectronica.com%2Fusercp.php

https://www.forosdeelectronica.com/...=FORID:10&ie=ISO-8859-1&q=potenciometro+sucio
https://www.forosdeelectronica.com/...=http://www.forosdeelectronica.com/usercp.php
https://www.forosdeelectronica.com/...%2F%2Fwww.forosdeelectronica.com%2Fusercp.php