I have slowly over the yrs ended w/a bunch of cool FX but now when I turn them on w/a Furman PC I get a loud thump. Some of the FX have 3 prong and some 2prong.Before I start ripping it all down any advice.Could I have a bad cap to ground etc.How does a studio keep it OK. Here a list,1)furman 2)Soho 4 tube preamp,3)ART Pitch tranposer/multFX. 4) Roland SRV 2000 Reverb 5)Roland SDE1000 DDL 6)Yamaha HD1500DDL.. 7)Digitec Time Machine for Loops 8)PS Systems Power Tool Reactive loadw/a 50 watt SS built in amp I can run both the preamp and my 100w Marshall into it and it has a FX loop that where I put the Chessy ART for the 12 string fx out to also run XLR line to a mixer if I want .It was made in early 1990's by Line 6 guys.in San Diego.:confused:Thanks