[rockadanny]

I recently purchased a pair of NOS Sylvania 6SL7GT tubes (JAN VT229) and just noticed a white haze covering some of the internals (getter, spacers).
What is this?
Is the tube defective?

[rockadanny]

Reply from the seller ...

That is normal.  Those are mica spacers.  Mica is sheet rock and is normally clear to cloudy, and sometimes if they have some gettering material on them from the factory, heat from operating the tube can make them look frosty white.  The mica is an insulator and is only there to hold the internal parts of the tube in place and keep them from touching each other.  The appearance of the mica has no effect on the operation or life of the tube.

 

[mresseguie]

Thank you for asking and for providing the answer. I have sometimes wondered this myself. 

[FullRangeMan]

Looks like the seller didnt warm-up this NOS for a few hours to activate the getter, may exist some gas inside due the getter has been inactive for many years, .

If you dont have a tube heater you need proceed with extreme caution to power on this tube from the hades, it good your amp have a soft start as the filament and cathode has been cold for long time.

The getter does not start cleaning internal air immediately after hot, the chemical process takes a few hours for the getter start gas cleaning cycle and convert it in solid sediments.

I read a recipe from an tube expert that a good way to activate the getter would be 3 or 4 warm-up cycles of 2 hours each before listen any music. Dont leave this NOS without surveillance in the firsts hours of warming up.
Wish you good look.

[bladesmith]

I recently purchased a pair of NOS Sylvania 6SL7GT tubes (JAN VT229) and just noticed a white haze covering some of the internals (getter, spacers).
What is this?
Is the tube defective?

How does it sound,  do you like it so far..?

V...

[rockadanny]

FullRangeMan - Thank you for the info. 

bladesmith - They sound great! These (6SL7s) are for the input side of the amps, the driver side of the amps are 6SN7s, power tubes are 6C33Cs, paired in parallel per monoblock.
Clean and clear, which is why I was shocked to see this white junk on the spacers. I immediately thought the tube had a leak, but not so, thank goodness.

[SteveFord]

If it had a leak you'd have white on the glass.  On the inside, of course.

[FullRangeMan]

Not if the getter are dormant, more than 6 months cold.