TrentBizzle":3sm5hupm said:
This was definitely very pronounced. It appeared to surround the entire tube. I had never seen anything like this before, so I was a bit puzzled.
There was no hum at all, just volume phasing in and out and some fizziness.
A blue glow is fine. If its a bluish violet glow you may have an issue as that can indicate an air leak in the tube. Bleu violet in mercury vapor tubes is fine. I have one of those in my tube tester. Swap your PI tube out and see if it fixes it. If not check your other pretubes.
BLUE GLOWS:
Blue Glows are not tube detriments per se. They are, however, suspects in the eyes of many receiving tube users for lack of a full understanding of their origins. There are several types of Blue Glow which can be described as follows:
FLUORESCENCE (Photo 1)- this type of glow is usually violet in color and most noticeable around the inside surface of the glass bulb. It is most pronounced on power tubes and is the product of electron bombardment of the glass taking place within the tube. It generally has no adverse affect upon receiver performance, and in fact, tubes displaying this phenomenon are particularly good with respect to gas content.
MERCURY VAPOR HAZE - is a blue-violet glow associated with those tube types which rely upon mercury vapor for proper operation. In such cases, the blue glow should be evident indicating proper operation. (Note from thetubestore: Mercury Vapor tubes are rare and almost never found in common guitar or hifi amplifiers)
GAS (Photo 2)- produces a blue haze, generally confined to the vicinity of the mount structure. The proper function of gas types such as thyratrons, voltage regulator and voltage reference tubes, requires the presence of this glow as an indication of proper tube operation. Some voltage regulators use neon instead of argon and as a result exhibit a pink-orange glow. It is, however, a distinct detriment in vacuum receiving types, where the presence of gas in large amounts can cause malfunction of the equipment.”
