[Chas]

I got this DC hum

 

Joke aside... Take a good look at the pin count on the sockets, be sure the connections are correct. Look closely, too, at how the solder has flowed. Certain brands of sockets are plated with a alloy that does not "wet" very well with common rosin core solder. the connection may look good but is not.. I have encountered such sockets in PC mount, the pin completely disconnected from the solder joint from heat cycling.

A LOT of small things can cause low volume, start with the bias on the output tube, too high (negative) will reduce gain, too low (more positive) will to but be accompanied with HOT output tube and reduced "B" voltages all over the set...

If the output tube is turning cherry red, it may also be ruined, as torn off cathode oxide (from high plate current) will contaminate the grid and make it an emitter.

Take and post some pix of your socket installation and solder work for criticism

Chas