I think I may have blown the output transformer on my blackface champ. It went from sounding OK to drastically losing power while playing to making crackling sounds and now it makes no sound at all. I replaced the tubes with a different set and still nothing. Using my handy troubleshooting chart says this seems to point to the OT. Does this sound logical? About how much should I expect to pay to get it fixed? Any suggestions for a good amp tech in the suburban Philadelphia area? Thanks!