I recently upgraded an Sheraton II with a new wiring harness, including pots, switch & plug, & a new pair of pickups. It sounds good, but shortly after the new components were installed, a buzzing hum started making itself heard. Grounding problem, I said, & returned to the techs who did the installation. They couldn’t hear the buzz. Life being much like a situation comedy, when I got the guitar home, the buzz was still there. I’ve had good service from this shop, so am inclined to give them the benefit of the doubt. On its return the buzz had changed both its sound & the conditions under which it appeared. Previously it was the same at all settings, & stopped when skin touched metal. Now that no longer stopped it, & it sounded different under different settings. Some were clear, some no longer worked at all. There was also a new sound, a gurgling tick-tock which sounded pretty digital to me. I now wonder if the problem might be with the amplifier. Before I rent an amp & guitar & try out diagnostic mixing & matching, I’d like to be better informed. Here are my questions: This is a five year old hybrid amp, part digital, part tube. How long does a typical tube last before needing replacement? The amp never had this problem before. Could it be that, before its upgrades, the guitar was never delivering enough signal to make an existing problem audible? I also tried an acoustic-electric guitar without hearing the buzz. Again, could that be due to insufficient signal from the guitar? Last, the guitar’s new pickups are not wax-potted. Reviews say this can, in some circumstances, cause them to become “microphonic.” I haven’t a clue what that might sound like, but is it worth considering? Thanks for your help!