Are my tubes going gassy?

[toshiba_nz]

So I got these 1940's tubes in what seemed unused appearance ...I started them off slowly, applied DC heater gently for a few hours, then brought the filaments up to rated voltage (DC) for 6 hours. Then applied B+ and grid voltage at 75% of max dispersion for ~6 hrs.

However, after using the tubes within spec for a week, I've noticed a slight change in appearance - a very slight whitish appearance on some areas of the glass (close to the getter) , where there was crystal clear glass previously.

Should I be worried?

 

[toshiba_nz]

Here is a pic- top left corner

 

[astouffer]

That doesn’t look bad. If the tube operates within spec it’s not gassy.

 

[Hearinspace]

What kind of tube is it?

 

[grovergardner]

A gassy tube will usually show blue glow inside the plate structure, rather than on the glass.

 

[toshiba_nz]

Thanks guys! They are hf200 (PP)

B+ 1455Vdc
G1 - one tube is at -56.9Vdc, the other tube is -57.8Vdc.
The pair drawing 82.3ma

 

[OldHector]

They are running a bit cold according to the design ratings. There are some tubes that have to have a glowing anode to have an effective getter, but cannot say if that is the case here.

 

[euro21]

With such negative grid voltage the "glowing anode" is unimaginable.
At positive grid voltage and about 300-400mA anode current is feasible.

 

[toshiba_nz]

I was aiming for an idle at 75% max dispersion =~80ma?