Quote:
Originally posted by wa2ise
Did they turn the heaters off along with the B+ to the TV only circuits? It'd be kind of a waste of power and tube life to leave them on. You'd need either a high current switch for the heater circuit or a separate heater transformer controlled by a lighter duty switch ganged with the TV/phono/radio function switch. If they did leave all the tube heaters running, you would have instant on of the TV once you were done playing records or the radio.....
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I'm not sure by any means, but given the fact that only one switch was used in these sets as the TV/phono selector, and the TV came on immediately after switching back to TV mode from phono or radio, I would think all tube filaments remained on when the set was being used as a phono amplifier or when the radio tuner was on. However, the circuit was probably arranged to open the B+ lines to the video and RF tubes, leaving the filaments on, during such operation. The sets I've seen with phono inputs usually used a push-pull, rotary or slide switch on the front panel in this position. For TV/radio/phono, however, most if not all sets used a rotary switch on the audio control panel (I have never seen or even heard of any American-made 3-way console which used any other arrangement, including push button switches, for mode selection). The arrangement you mention, using either a separate high-current switch for the filaments ganged with the B+ switch or a separate switched filament supply for the RF and video tubes, would have been, IMO, unnecessarily complex and would have added a certain percentage more to the cost of the set, not to mention being wasteful of power, also as you mentioned.