I am assuming that the tubes all light? I.e., it the lights are on but no one's home...
I will disclose to you the expert's secret vintage tuner repair trick
If you haven't done so yet,
one at a time, remove each tube and clean the pins (I use a Q-tip and DeOxit and finish with a paper towel to remove any residual). Clean the sockets, too, if you can (a dental pick comes in very handy for the latter). Reinsert each tube after cleaned. When they're all done, try the tuner again.
I've "fixed" a number of old tuners this way.
Of course, if you reveal this secret, we'll have to deal with you harshly.