Re: deville problems... floppy sounding
Aside from tubes, other possibilities that are common to these amps include an open (one of the two) PI plate resistor, a fried power tube screen resistor (again, one of the two) or a fried block resistor on one (yet again, one of the two) of the supply rails that power the effects loop, channel switching and reverb.
It probably needed new tubes anyway so that was a smart place to start.