The AA8V Wingfoot 813 Amplifier
High Technology Of The 1950s In The 2000s
by Greg Latta, AA8V

Power Connector Circuit Description and Schematic Diagram

Click On A Section of the Schematic Below for Information on That Part of the Circuit:

Click here for a higher resolution schematic.

Circuit Design Considerations:
The power connectors connect the power supply to the 813 amplifier and the AC power. The high voltage connectors are James Millen type 37001 "Safety Terminals", which are the only kind available that can withstand the full plate potential. They are also used on the amplifier itself. Amphenol type MS connectors are used for the remainder of the connections. These are expensive, but the best available.

Click here for pictures and information on the matching Wingfoot 813 Amplifier

AC Connector: AC connector P3 is a 6-pin Amphenol Type MS receptacle connector. These connectors were relatively expensive, but could be obtained surplus at a reasonable price. Pin B is used for the AC neutral connection, and pin D is used for the chassis/AC ground connection. Pins E and F are used for the AC hot connection. Two pins were originally used in anticipation of 240 volt operation, which was never implemented. Instead, in the mating Amphenol plug, pins E and F are tied together in parallel to the AC hot lead. Each then feeds AC to the power switch S3.

AC Neutral Connection: The AC neutral from pin B of P3 is fed to one side of T1 and T3 and also to one side of the OPERate/TUNE switch (S2A).

Power Switch: Switch S3 is a simple double pole/single throw (DPST) toggle switch. A double pole switch was used in anticipation of 240 volt operation. However, 240 volt operation was never implemented, so the two switch sections are run in parallel. The switch receives AC from pins E and F on the AC connector, and feeds the AC to fuse F3.

Fuse: Fuse F3 is a 6 ampere slow-blow unit that protects the entire power supply. One end of F3 is connected to the AC hot lead through the power switch S3. The other end of F3 then feeds the hot side of T3 directly and the one side of T1 via the inrush delay circuit.

Fuse Holders: A 6 Ampere slow-blow fuse is used for the main fuse at F3. A 1 Ampere fuse is used at F2 to protect the current inrush circuit. F1 is used to store a spare 6 Ampere main fuse.

High Voltage Output Connectors: The high voltage connectors and connecting cable must be able to safely withstand the full output of the plate supply, which can exceed 2500 volts. The only connectors that can safely withstand this voltage are made by the James Millen Co. and are known as "Safety Terminals" type 37001. RG59 coaxial cable is used to make the connection to the 813 amplifier. This type of connector is also used on the amplifier itself. J3 was originally for the screen voltage output, but it was decided to run the screen output to connector P1 instead, so J3 is not used.

Screen and Bias Output Connectors: Screen and bias output connectors P1 and P2 are also Amphenol Type MS receptacle connectors. As mentioned before, these connectors were relatively expensive, but could be obtained surplus at a reasonable price . Either connector can be used, though screen output is only available at P1. In practice, P2 is used, since the 813 amplifier uses the 813 as a triode and does not use separate voltage on the screen grid.

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If you have any questions or comments, you can send E-Mail to Dr. Greg Latta at glatta@frostburg.edu