silvertone 1484 looses volume

[allsavy]

I'm trying out a 1484 twin twelve. It is all original. I'm getting a lot of odd noises that sound like speaker buzz for a portion of the bass notes (it is not the speakers). Also after about a half hour of playing there is a loss of volume. I'm sure it needs a cap job and shouldn't be running it but I'm trying to get a feel about wheather or not to try to restore this thing or just sell it as is?
Resistors throughout seem to have drifted (some by a lot).

What are the major things tend to with this model? (aside from the OT)

thanks.