[Hallicrafters] S-40A noises

[TC Dailey]

Get some DeOxIT contact cleaner - with the radio OFF, pull each tube out 
(move in a circular motion, while pulling up), clean the pins, and "annoint" 
each pin with some DeOxIT between your fingers - now, before putting it back 
IN - and using a toothpic or small applicator, moisten each tube-pin 
receptable, as well. (INDIVIDUALLY - DO NOT SPRAY).  Push the tube IN and 
pull it OUT a few times each.  Now, see if the noise went away.  If not, at 
least you won't have noise due to poor conduction on oxidized connections.

Tom