I thought I would pass this along. For the past year I have been having a rattle type noise that comes and goes. It wasn't a cabinet rattle and for a while I thought it was a loose plate in a tube. I swapped tubes but the noise was still there. My guitar player has the same amp with the same problem. I finally figured it out. It turned out to be an ill designed Ruby Tubes Chinese ceramic power tube socket. If you look close at the photo you will see that the 4 bend over metal tabs do not line up with the slots on the ceramic socket. You can see this clearly on the bottom two metal tabs. They are suppose to lock down in the slots on the ceramic section. After the socket heats up and cools down the ceramic part starts moving around and eventually rattles. I have heard this noise in countless new Fender amps over the past few years and couldn't figure this out. If you are hearing a weird rattle - find the low note or chord on your guitar where it's the loudest and try grabbing the power tubes with a t-shirt, rag, etc. If the noise goes away it's a defective tube socket. I'm glad I work on my own amps and was able to track this noise down. I bought a few high grade sockets and did the repair. I can't imagine how much bench time would have been wasted trying to track this down. Now the rattle is gone. I blame this on quality control and Fender trying to save a few bucks. How many amps were returned because of these cheap ass tube sockets. I have never had this kind of problem with any of my vintage amps. Cheap tube sockets are $1 while really good ones are about $3. This kind of cutting corners is what gives companies like Fender a bad name. The keys on my $400 Squire Jazzmaster are the worst I've seen on a guitar while the keys on my $269 Epiphone 12 string are great. Quality control is the key here.