26-10-2016, 04:06 PM
Bob,
if you have two transformer windings with voltages A and B and connect them together in series, you can get two results.
If the voltages are in phase, the two voltages will add together so the result is A + B.
On the other hand, if the windings are out of phase, they will subtract, giving A - B.
That is what is happening when you operate that switch: in the centre position the two AC voltages appear out of phase, as far as the valve is concerned, so the 1V winding is subtracted from the anode supply i.e.: the sum goes negative - in other words, down. When the switch is operated the 1V signal phase is reversed so that they add - the sum of the voltages now goes positive - in other words, up.
I've simplified this to hopefully make it easier to understand - it is really the anode current that we are interested in and the meter needle should show an increase when the switch is operated - in other words the current (which is now a pulsating DC that does not go below zero) increases or moves in a positive direction, as indicated by the meter.
if you have two transformer windings with voltages A and B and connect them together in series, you can get two results.
If the voltages are in phase, the two voltages will add together so the result is A + B.
On the other hand, if the windings are out of phase, they will subtract, giving A - B.
That is what is happening when you operate that switch: in the centre position the two AC voltages appear out of phase, as far as the valve is concerned, so the 1V winding is subtracted from the anode supply i.e.: the sum goes negative - in other words, down. When the switch is operated the 1V signal phase is reversed so that they add - the sum of the voltages now goes positive - in other words, up.
I've simplified this to hopefully make it easier to understand - it is really the anode current that we are interested in and the meter needle should show an increase when the switch is operated - in other words the current (which is now a pulsating DC that does not go below zero) increases or moves in a positive direction, as indicated by the meter.
