My 1970 Twin just got back from a checkup. It has new power tubes but all original preamp tubes. It has a very low noise floor, except when I kick on the reverb with the effect dialed up past 5 or so. At that point, I get a fair amount of hiss. I tried deoxit on all of the reverb connections, which seemed to help a little, but there's still more noise than I prefer. Should I swap out the reverb tube next, or is this normal and I just have to get used to it? Thanks!