Tung-Sol kt170 tube started glowing brighter

Your amplifier is rated for use with either 6550C or KT88 output tubes. It is not designed to handle the current draw of the KT170 output tube. In addition, as previously mentioned, your amplifier requires re-biasing when changing output tubes. I would heartily recommend pulling the KT170 tubes before the amplifier goes up in smoke.

The designer said the KT170 tubes would work. They are a new tube to the market. These were brand new and played for 50 hours for this to happen. Of course I biased the tubes. I’m pulling the amp and placing my solid state Arye amp back in. I’m almost positive I’ll go back to KT150 tubes. I don’t hear the prat that I got when I had KT150 tubes installed. They needed replaced, hence here I am.

You sure it's not just part of the heater filament being more exposed?

I don't know tubes to this extent. This is why I posted. I do know that a repair of the amp is forever and $$ so I'm reaching out for help.

KT170 tubes have been around for several years. Have you moved that tube to another hole to see if it is the tube or your amp?