|
If it's a series heater set you don't need a transformer or any modifications to run a higher voltage heater... Provided that the heater current ratings of both tubes are the same. If it has parallel heaters and a power transformer you can harvest 6.3V from the signal tube winding... Either way it's doable, and probably more practical than holding out for a 2.68V part.
A few years ago I took a series heater Philco Predicta Tandem and swapped the 600mA 2.68V heater CRT for an otherwise equivalent CRT with a 6.3V 600mA heater, and it automatically got a 6.3V drop across its heater.
Basically on a series heater set the sum of the heater voltages are supposed to be close to the design center wall outlet voltage and all have the same current rating. The which tube gets how much voltage is a function of the design resistance of the tube and the current. They designed those sets to put up with at least a 15℅ low or high wall outlet voltage, and back in the 50s the assumed average wall voltage was 117V... Today assumed average wall voltage is 120V the extra 4V the tube soaks up should compensate for today's higher line voltage perfectly.
If your TV tech doesn't understand series circuits well enough to realize this then I would be hesitant to let him work on ANYTHING I own. The principles and properties of series and parallel circuits are almost as basic and fundamental to any electrical system as ohms law... A TV repair man not knowing them is like a fish that doesn't know how to swim.
|