Quote:
Originally Posted by peverett
I have seen Motorola use two 3CB6 tubes in series in a transformer set where most of the tubes are 6 volt.
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I can see an engineer doing a trick like this to create a centertap effect for the heater supply. Tie the midpoint between the 3CB6s to ground. Then the rest of the heater supply will have 3.15VAC to ground on both sides. I've done something similar in audio equipment, used a 12AU7 tube powered by a 12.6VAC transformer winding, and the pin 9 heater tap (provided mainly to allow the use of 6.3VAC to run the heaters) I connected to ground. To create the effect of a centertapped heater winding. So I only have 6.3VAC floating around the audio circuits.