EFJ Viking 500 Power Supply Project - RT's Radio Home Page
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EFJ Viking 500 Power Supply Project
Amateur Radio > Vintage Transmitters
Background:
The EF Johnson Viking 500 AM/CW transmitter was manufactured as a set of two major components, the Desktop RF Deck and the remote Power Supply/Modulator unit. These two units being connected together by plug-in cables. The separate units were necessary since power supply itself weighs around 120 pounds, while the RF deck weighs around 65 pounds.
Manufacture of the Viking 500 ended in 1964. Over the years, AM operation was superseded by Single Sideband (SSB) operation, so the older AM rigs fell out of favor and were likely relegated to the garage or other storage area and possibly forgotten. When the owner passes away, the family members are completely unaware that the big, heavy unmarked power supply is a necessary component serving the RF deck, so many of these were sold separately or sadly, went to the landfill.
The Viking 500 #2 RF deck detailed on this site was separated from its power supply at some point in history. The RF deck is now operational, so the construction of the new power supply/modulator unit is coming soon and will be detailed below.
The New Power Supply:
Here is the topside view of the power supply chassis from a Johnson Invader 2000. It is in the process of being converted to operate the Viking 500. All components have been carefully removed from the chassis. It has some small areas of surface rust. Some sanding marks from previous repairs were found; some of these were successfully removed by the buffing wheel.
Underside view of the power supply chassis.
These are the original components from the underside of the chassis.
This transformer suffered a catastrophic event! It is not original to the power supply, and it has no center tap for the 2.5 volt secondary; this may be what led to the burnout. It will be discarded, and the new rectifiers will be solid state. Inrush current limiters will be installed at the 240 volt line to the high voltage transformer to limit the instantaneous load at keyup. These tube sockets will carry the 811A's in the modulator.
To be continued.....
Chuck Hurley, K1TLI, who has done several beautiful restorations to EF Johnson equipment is having a new batch of Viking 500 power supply chassis made. I have sent a deposit and hope to have one by mid-December 2025. This new chassis will replace the Invader 2000 supply chassis shown above.