Purple glow just inside the glass is caused by electrons hitting the side. This isn't a problem. Purple glow within elements indicates a gassy tube. A gassy tube shouldn't be used as they can get worse and draw too much current.
Norm
:HI. been busy recapping my forth atwater kent 55 radio. was wondering thou why does a matching set of 45 tubes glow purple?? if i switch them around no purple glow. these 45 tubes do that in the other three radios. also this model 55 works real well. the antenna post are connected together and picks up a lot more than my other ones. well back to the bench. thank you
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