[R-390] Tubes glow blue

[Flowertime01 at wmconnect.com]

Scot,

Not such an odd observation.
The question is the noise level of the tubes.
After you let a couple burn in for some hours, how is the signal to noise 
performance of the receiver? If the tubes loose the blue glow and are not noisy 
let them be. The blue glow is ionized gas. That gas is being smacked by 
electrons in transit. Smacked gas makes noise.

A couple dead horses on the subject back when. Warming the tubes with a Zippo 
lighter will take the blue glow out. The reason this works is, you heat the 
getter stuff and it gets some more of the gas. At least enough of the gas is 
absorbed so the gas is not visibly glowing blue. In old tubes not heated through 
use, the getter stuff can let some of the gas loose. Very little gas and very 
long time (years) to get loose.


Your NOS may not be NOS but service pulls and stuffed back in the box. They 
could be victim's of old age. If the emission is OK and the noise level below 
your acceptance use them.

Roger KC6TRU