noise question related to 6a8g tube

Restoring my first radio, a GE G53. Got it mostly rewired and completely recapped. It plays great except for one quirk. If I very lightly tap on the 6A8G tube, which is defined in the schematic as the converter and oscillator, i get a hissing sound with each tap. I checked the connections and the tube socket. No problems. I also discovered that if I tilt the chassis, the hissing is constant. It's a very faint hiss, not even close to covering up the signal. Could it be a problem within the tube simply requiring replacement to cure the problem?

Dirty tube socket pins?
Try using electronic spray cleaner on socket, and, tube pins. Wiggling tube will also cause noise on dirty sockets.
If not that, tube is bad.
Bill Cahill

It was the tube. And what a difference the new tube made. Now to get on with alignment. It's obvious someone thought the adjustment screws were "loose" and needed to be tightened down.

Congrats!
Bill Cahill

Wait.
What do you mean, adjustment screws?
You don't tighten adjustment screws.
They are set to a certain capacitance, by adjustments and if slug tuned coils, an inductance balance to align the IF transformers, Rf Transformers, Oscillator and RF variable capacitors to make them track. If you change those you may be sorry (unless you have had previous experience)

Most screws are one of two types, one to adjust a capacitance, the other type is a screw attached to an adjustable iron powdered core.

These are needed to bring the alignment of stages, to make the dial track correctly and increase sensitivity and bandwidth.