No. Remember there will almost certainly be Channel A and B level controls on the rear of the unit by the audio outputs -- make sure they are both turned up equally. The two shielded tubes closest to the audio output jacks will be the final audio stages for both channels -- make sure those tubes are good as well.
Finally, if none of the above resolves the issue, then determine if the problem is present just in stereo mode, or in both stereo and mono mode. If the problem is present in both stereo and mono modes of operation, then the problem is almost surely associated with the audio output stages. If just in stereo mode, then the multiplex decoder will be the go-to target.
Of course, make sure all the tube sockets are clean, all tubes are lit up, etc. For whatever the reason, tuners seem to be plagued with more tube socket terminal and tube pin corrosion than any other piece of equipment I've seen -- and I mean to the point where the tubes won't light up. So while cleaning sockets, switches, and controls in amplifier equipment (when done) is invariably a measure to eradicate static or an occasional channel drop out, in tuners, it's sometimes needed just to get the darn thing to even work at all.
Dave