Pilot TV-37 question

[Electronic M]

Originally Posted by bigaudioal

If I do have a weak CRT can I then put in a CL-90 thermistor at the AC line before the filament string for a solution to the filament voltage spiking on power up?

Not a good idea! The voltage on any given series heater at any given instant is highly dependent on the warmup state of the other tubes, and unless they all warmup in exact synch* there will be over and or under voltage transients on the heater (which is why TVS diodes and or filament transformers are added to these sets).
*The odds of that, if not slowly variaced, are comparable to those of turning off your clothes dryer and finding all the clothes inside neatly folded and stacked!