EF Johnson Viking 500 #2 - RT's Radio Home Page
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EF Johnson Viking 500 #2
Amateur Radio > Vintage Transmitters
The latest project is yet another Viking 500. This unit will be a real challenge because no power supply/modulator unit came with it. The consensus regarding why there are so many orphaned RF units around is due to families of amateur operators who have passed on do not realize the big, heavy box on the floor is a neccesary component to the radio box on the desk. The units become separated, and the power supply will go a different direction than the RF deck.
This Viking 500 has been restored on the exterior and was nicely done; in contrast, it is an electrical challenge on the interior. Strange modifications, circuits removed and others added. The first find was a hard-wired short on the 120 volt line; two broken switches, and the VFO board had burned. After repairing these, it more or less "works" now but with low power output with good tubes.
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 components from the underside of the chassis. The goal is to incorporate as much of the wire loom into the final design as possible. Of course, the capacitors will all be replaced.
This transformer suffered a catastrophic event! It is not original to the power supply. Apparently, it has no center tap for the 2.5 volt secondary; this may be the cause of 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 instatntaneous load at keyup. These tube sockets will carry the 811A's in the modulator.
To be continued.....