[timmy]

Originally Posted by Yamamaya42

Or, (speculation), red is the weakest, and if... I mean IF the heater voltage is a tad low on the tester vs running at full power on a TV, or any other known good state, it could be the equivalent to a “life test” where the heater voltage is deliberately lowered to see which tired gun drops of first, not saying that this IS what is happening, but a simple DVM test will make sure, cause you never know what the voltage is at the tube test socket for sure.

I’ll have to check the voltage but if all 3 are good then it’s a mystery