What am i doing wrong?

[compucat]

Originally Posted by old_coot88

I had a bizarre case in the shop one time, a series-string B&W TV that was turning itself on and off, not abruptly like with the switch, but fading in and out. The heater string was doing it. Finally traced it to the CRT heater which was "blinkering" by thermal expansion/contraction just like an auto turn signal blinker. Never seen a case of that before or since.

I had that happen in my Sparton AA5 radio. After a while of normal function, the set would go dead. If I left it alone, eventually it would come back on its own. One of the tubes developed an intermittent heater.