Is this normal for rectifier tubes?

[ElectricTurkey4369]

Im not used to rectifier tubes, so i dont know. When I use recto tracking the rectifier tubes dont seem to light up, theres a small glow inside and i dont know if thats normal or not...
Thanks guys!

 

[EtherealWidow]

Totally normal. Don't worry about it. Trust me. I'm an expert.

 

[espboogie123]

Capture some pics. Try with lights off no flash. Pics of tubes are always nice. As long as the amp sounds ok, every tube will have a different natural glow. A non glowing tube, or a red plated tube or purple/blueish glass tube can be something to worry about. The blue/pinkish glow is an indicator of the tube becoming "gassy" or losing it's vacuum; this can be caused by a structural failure in the tube (broken or cracked glass).

 

[94Tremoverb]

Purple-blue or plain blue glow strictly on the inside of the glass is not anything to worry about! In fact, it's almost always a sign of a good tube with a good vacuum and is caused purely by fluorescent minerals in the glass being hit by stray electrons. It's also one of the most beautiful colors there is, if you see it in the dark . Slightly greenish or plain blue faint glow inside the plates is also usually nothing to worry about, it's quite normal on many power tube types.

Purple or pinkish-blue glow that's clearly inside the tube structure and not just on the inside of the glass is definitely something to worry about though - that does mean gas, and is usually a sign of imminent serious failure, or it already having happened.

Google image search 'blue tube glow' for some nice examples of both main types.