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EF Johnson Viking 500

Amateur Radio > Vintage Transmitters
The E.F. Johnson Viking 500 transmitter was produced during the late 1950s through about 1964; it runs both AM and CW modes.  This is a photo taken shortly after bringing it home.  Sources indicate production of the Viking 500 was limited to 865 units, so it is fairly rare.  The transmitter employs an Eimac 4–400A tetrode tube in the RF final; modulation is provided by a pair of RCA 811A's.

In 2022, I decided to get a plate-modulated AM station up and running again.  A couple of long-suffering Viking Rangers came home first.  In January, 2023, I found the Viking 500 above on Craigslist.  I quickly contacted the owner and met with him.  He had other rigs to sell, so a few more boatanchor rigs came home as well.  

The underside of the power supply as found.  

This is the completed power supply, underside of the chassis.  
The major change/mod is the use of radial lead capacitors for the high voltage instead of those with axial leads.   

The rationale for not using axial lead capacitors:
1:  They are very expensive at $30+ each.
2:  The radial lead capacitors installed are around $4.00 each and have better ratings, including longevity.

The  new capacitors are lightly clamped into place by a square-sectioned  plexiglass rod; radiused notches were cut in to cradle the capacitors.   The notches are felt-lined, and there is a strip of felt under the  capacitors.  The leads are sleeved with insulation from 5KV test lead  wire.  The assembly is held in place by three longer screws with  standoffs to limit clamping pressure.

The  other mod is the delay circuit for relay RY302 which sequences the  release of that relay to prevent arcing.  No arcs have occured.  (Thank  you WQ9E!)

The front panel appeared to have light rust coming through the paint.  I used automotive polishing compound and worked carefully to avoid the graphics as much as possible.  A light coat of automotive paste wax finished it off.  The brownish rust is gone.

Here is a before and after of the VFO cover.  Here it has some imperfections in the paint.  I do not know what these are; however, I used the polishing compound on it as well.  Before (Above):
Here is the VFO cover after polishing.
I had paint mixed to match the E.F. Johnson Maroon.  The 500 Case needed repainting as do all of my Johnson Viking gear.  Here it is just after painting.  The front rim of the Johnson Viking case is intentionally left unpainted to make electrical contact with the front panel.  This is necessary to assure a good, RF tight enclosure.  This case is masked off at that location.  
I brought the Viking 500 home in January, 2023.  Here it is May 16, 2023, and the power supply top and bottom covers are finally back on.   

Here is the finished Viking 500 in the shack.

The Viking 500 Power Supply.  The power supply alone weighs in at about 120 Lbs.  This is the main reason it is on a cart under the desk, on the floor.

The 811A's glowing in the background assist the other tubes in this transmitter in heating the shack in the wintertime.

Johnson Viking 500 Startup:

I had been looking for a "500" since the late 1970's. After reading of the arcing and sparking complaints by owners over the years, it seemed the 500 was of poor design.  Thanks to Mike and Rodger from the Antique Radio forums, I made their suggested modifications to the 500 that would prevent this erratic behavior.   

After many weeks of work on the 500, it was finally time to fire it up.  Well, hopefully fire would not be involved!  At first, the High Voltage fuses were left out, and it was energized only on the low voltage circuits.  The filaments on the tubes lit up normally, the panel lamps came up, and the fan whirred along nicely.  I ran it like this for several hours.

High Voltage testing:  I’d never thrown the switch on a Viking 500 and didn’t know what to expect.  Re-installing the HV fuses, I hesitantly turned on the keyswitch.  Immediately, a sharp snap and loud buzz accompanied the lighting of the 811A filaments—I quickly shut it down!  The sound was from a relay in the power supply that was merely mis-aligned.  The relay aligned, the next test started out fine—a smooth startup!  Again, I let it cruise for an hour or so before keying up.

The first key up followed going through the manual and setting all controls for the band selected.  Finally getting the nerve to key this beast up, I gripped the D-104.  A click resulted but no response from the transmitter—no high voltage!  My heart sank; is this a bad high voltage transformer?  Opening up the power supply, the HV transformer has continuity on the primary and secondary windings.  Further tests showed no voltage is getting to the HV transformer primary.   The culprit was the relay serving the HV transformer was not making contact.  Some massaging of the contacts, and all is ready for testing again.  

The second key up, we have high voltage!   Now it was time to check to see if my worst fear would be realized: the condition of the modulation transformer.  This transmitter had been stored in unfavorable conditions for many years; the rusted chassis indicated moisture had been present.  I keyed up and tuned up to 100watts.  Slowly turning up the audio control, I tested the microphone.  We have audio!  The modulation transformer is good!  

Retuning, I found the transmitter will produce 300 watts of plate modulated AM.  Testing on the air, it is a very smoothly operating transmitter and gets good audio reports.

This entire project has been worth every hour and dollar invested.
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