Charles, this question has been gone over pretty thoroughly over at A.R.F.
http://www.antiqueradios.com/forums/...p?f=3&t=182773
The main consensus is if it checks good then it's good, the glow on the glass in normal, down inside the elements is Gassy and bad.
I've never seen a tube with purple inside the elements check good.
Some folks even think a purple glow on the surface of the glass indicates a very hard vacuum.
Jon, I'm not sure if your afraid it won't work or just looking for the Scientific answer to why it glows.
I'm quite confident it will function in your set, the Scientific answer will have to come from someone else I'm afraid.
Dammit Jim, I'm a Mechanic not a Scientist!
