PLASMA AMP TO 40 METER CONVERSION

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I found this 3CX3000F7 RF Deck from a 13.56 mHz Eratron Model 80030 Plasma Generator.  I was originally planning an easy conversion to 20 meters, but abandoned the idea since I am a night guy and 40 is a much better band at night.

           ORIGINAL UNMODIFIED 13.56 MHZ RF DECK

            
       Front view                Front-top view                 Top view                   Bottom view 

                     CATHODE CIRCUIT CONVERSION

Original 13 mHz pi-network cathode circuit:

           
The PI-network capacitors have very short shafts with slotted ends, that extend only through the RF compartment; however, there are two holes in the front panel to allow for screwdriver adjustments of these capacitors.

Completed 40 meter pi-network cathode circuit values:

        
Removed the original 3 turn coil and replaced the original doorknob caps with 650 pfd units.  Wound a 9 turn coil of #8 bare copper around a flashlight.  Hooked up the MFJ-259 and the 51 ohm loading resistor and by trial and error, trimmed down the coil until I found 6 turns would be perfect.  ( 6 turns, 1.75" diameter, 2.25" long)  Low Q, flat from 6.8 to 7.5 mHz without retuning.

                       PLATE CIRCUIT CONVERSION

Original 13 mHz pi-network plate circuit:

Completed 40 meter pi-network plate circuit values:

            
The original pi-network output caps had fixed values to feed a fixed load of 50 ohms.  To accommodate loading into other than 50 ohms, I added a 150 pfd breadslicer.  The original 100 pfd units were replaced with 200 pfd units.  The resulting coil was 4.25" long, 3.75" in diameter wound with 1/2 in wide silver plated ribbon (aprox 4.6 uhy).  Also added was a 90 microhenry protection choke.

                     INSTALLED TURNS COUNTER

   
There was no room inside the cabinet, so the final amp pi-network turns-counter was externally installed.  It's ugly, but it has a very solid connection to the vacuum variable.

         INSTALLED TUBE COOLING BLOWER

    
Installed and spray painted (Rust-oleum flat black) 3/4 inch plywood shelf inside a 6 foot relay rack using four 3" x 3" angle brackets.  Cut a rectangular hole in the plywood shelf and added the Dayton 4C870 blower motor:  1/10 HP, 1570 RPM.  Fan is 6" in diameter and 4" wide.  RF Deck will be slid over hole in plywood, as the hole was cut to line up with the tube.

   CONSTRUCTED 2 AMP PLATE CURRENT METER SHUNT

        
The process involved putting the test meter in series with a known "standard" 2 amp DC meter in series with a power source that could be varied.  By trial and error, a certain length of shunt wire will make the test meter read the same as the standard meter.  I found that a 3 foot length of #20 hookup wire did the trick.  I also added back to back diodes for meter protection.

BUILT PUSH-TO-TALK CONTROL CIRCUITS

         
Using a series resistor in the DC path, the power supply provides about 17 VDC to turn on the 12 VDC relay and then drops to 8.5VDC to hold it on.  I expect the push-to-talk wire to be quite long from the shack to the garage.

          3CX3000F7 FILAMENT TRANSFORMER

Expecting a 120VAC transformer, I was surprised to find it was actually built for 220 VAC.

      BUILD HIGH VOLTAGE POWER SUPPLY

            
5000 volt supply       Filament and blower control

installed the Plate transformer:

     
260 pounds !!  Primary:  198-208-218-219-230-241 VAC.  Secondary: 2378-1980-1694-0-1694-1980-2378.  In a capacitive input, full wave bridge configuration, this transformer would yield between 4970 to 6724 VDC.  At 2 amps CCS, this transformer will loaf (be asleep) at legal limit power.  Serious overkill, but the transformer was free ! 

installed transformer primary control module:

         
Built the modular control unit on a 7.5" X 17" painted 3/4 inch plywood board.  Has 30 second delay step-start via a 25 ohm resistor and a shorting contactor.  Connected the control module to the AC power subpanel via a 50 amp dryer plug and socket. 

Installed K2AW rectifiers and computer grade filter caps:

        
Installed (8) K2AW rectifiers on a 5" x 8" x 1.25" aluminum heat sink and wired them in parallel.  Installed (16) 1900 MFD @450 VDC computer grade caps on a painted 3/4 inch plywood and wired them with equalizing resistors.  Total value is 118 mfd @ 7200 VDC.