This is a question in regards to a Canadian Westinghouse model 54 (schematic here).Alot of radio seem to use this scheme for biasing the output tube.If you look at the schematic the choke (field coil in this case) is on the negatve side and on either side are resistors( 1 meg and 175000 ohms)and at there junction is a 250000 ohm resistor with a.05 mF cap that goes to the grid resistor of the 41 output tube.Can anyone clarify how this actually works and what is going on here and how this creates bias.

Hi Chris

Center tap of the high voltage winding on a power transformer is the most negative point in a radio. The choke is between this point and chassis ground. Since a radio draws current voltage is dropped across this choke making chassis/ground more positive than CT.

Radio circuitry is referenced to chassis/ground. This means center tap of the high voltage winding, other side of choke, is negative. This negative voltage is used to bias output tube.

http://www.nostalgiaair.org/PagesByModel/128/M0030128.pdf

Norm

:This is a question in regards to a Canadian Westinghouse model 54 (schematic here).Alot of radio seem to use this scheme for biasing the output tube.If you look at the schematic the choke (field coil in this case) is on the negatve side and on either side are resistors( 1 meg and 175000 ohms)and at there junction is a 250000 ohm resistor with a.05 mF cap that goes to the grid resistor of the 41 output tube.Can anyone clarify how this actually works and what is going on here and how this creates bias.
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