i recently bought an active 4 string vester(looks like a warwick thumb) i got it really cheap. there are 3 pots one is frozen up and another just dont do any thing.the volume is the only one that works. i would like to replace them because the bass is other wise in great shape. idon't know what pot is what other than the volume wich is in the middle. can ny one tell me what the other two are and where they are located? i'm thinking of replacing them myself but i'm still undecided.is it difficult? what do shops usually charge to have this done? i may replace the pups too . thanks for any help.