Ampeg V4 Bias Circuit Question

[Diablo]

I've been looking over the 1971 Ampeg V4 bias circuit and one thing puzzles me. The bias is energized when the main power switch is on and the standby switch is in the open position. If you look at the top of the bridge rectifier you can see where the current comes from the top of the secondary winding on the power transformer. I don't understand where the circuit gets completed to the bottom of the secondary winding on the power transformer. I've had an electrical engineer at work look over the diagram and he can't figure it out either. What are we missing? Here's the schematic below:

http://members.aol.com/portaflex/schems/v4powa.gif

[loudthud]

Those Joe Piazza schematics sometimes have mistakes. There should be a ground at the center of the hum balance control. What makes the bias circuit work when the standby switch is open is the fact that the power tubes and other loads pull the B+ towards ground and the .047 cap still couples AC to the bias rectifier.

[Diablo]

I still don't see how the AC completes a circuit from the bias back to the bottom side of the secondary winding on the PT. I see only one side of the connection to the transformer. I looked at the original Ampeg schematics too, and they show the same circuit as Joe Piazza for the bias supply.

[Bruce / Mission Amps]

Through the diode in front of the standby switch.
The two anodes of the FWB rectifier are connected to the bottom of the filter caps... and then grounded for a standby switch.

[Diablo]

Through the diode in front of the standby switch.The two anodes of the FWB rectifier are connected to the bottom of the filter caps... and then grounded for a standby switch.

Thanks Bruce for taking a look, but I still don't undestand. Is any current flowing through the diode in front of the standby switch when the standby switch is open? When I look at the circuit, I don't see a return path for the bias circuit until the standby switch is closed, and the tubes powered up.

[Borg54]

Put a meter on. When in doubt follow the circuit through.