The power transformer in this improvised power supply will be used to replace the power transformer in the Johnson Adventurer. This configuration used a bridge rectifier with some additional windings on the transformer to develop @1200 volts. This was used as a temporary supply for the 4-400 transmitter at one time. This transformer was also used in the power supply of my 4CX250 two meter amplifier. The Johnson Adventurer will use it in a center tapped supply to develop 500 volts and the voltage for the filiaments.

Looking in the back of the rack the SB 200 can be seen mounted at the top. The relay box mounted on the back switches the Johnson Adventurer in to the linear transmitters internal dummy load.

In this view the Johnson low pass filter can be see in the center. The filter capacitors on the left are part of the modulator power supply. The relay box mounted on the back of the Johnson Adventurer switches the modulation monitor input between the linear AM and the 4-400 transmitter.

This is looking at the bottom of the transmitter rack. At the bottom of the rack is the VFO power supply, external modulation components and the power supply for the AM stereo equipment. Out of view is the modulator itself and a T/R relay switching deck. The new power transformer is too big to fit inside the Johnson Adventurer cabinet. It has to be mounted externally... but where????

This is the Johnson Adventurer from the linear AM transmitter. You'll notice a few differences from the other Johnson Adventurer. A number of relays have been added for T/R switching. There's an additional transformer to power the relays, the 5U4 has been replaced by solid state rectifiers and the output DC blocking capacitor has been replaced by a large transmitting mica capacitor. Notice the black tar that has puked out of the power transformer. The chassis under and around the transformer was black.

And the transformer tar even found its way to the underside of the chassis.

And all over the bottom of the cabinet in the transmitter.

The transformer wired up with connectors to allow easy removal from the rack.

The Johnson Adventuer running on the bench with the new power transformer. All parameters are exactly the same as with the old power transformer. The old transformer has been removed and the chassis cleaned. Both the 6AG7 and 807 were replaced as they were also victims of the transformer failure. The Johnson can now run 100% duty cycle with barely any temparature rise in the power transformer.

The power transfomer in its new home on top of the VFO power supply.

The death toll. The power transformer failed causing over voltage and burning out the filaments in the 6AG7 and 807. That also burnt out the pilot light. Then the fuse blew.

More to come!!

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