gofar99 Messages: 1949 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi everyone one of my worst fears (others no doubt share it) seems to be happening. Tungsol KT120s are red plating well below their rated dissipation. Seems like at 60-70%. Not good for class A amps. KT150s are being received that are just plain defective. A UK licensee of some of my designs has reported the problems starting about 4 months ago and now it is a thread on diyaudio.com (see the link).
My suggestion is that if you get any tubes that red plate or just don't seem right...send them back until you get good ones. Maybe the suppliers will get the word and not accept seconds from the factory and QC will improve. There is always hope.