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THE AM BULLETIN BOARD => Technical Forum => Topic started by: KW6T on January 06, 2023, 11:06:16 PM

Title: Johnson Viking 500: New owner
Post by: KW6T on January 06, 2023, 11:06:16 PM
Good day all.
I have been a Johnson Viking transmitter buff since running a Viking Ranger on CB in the early 1970ís.   After getting my ham license, I bought a friendís Viking Valiant in the mid 1990ís, recapped it.  The modulator was modded, so I put it back to stock; unfortunately, it produced no audio.  Thinking is was the modulation transformer at that time, back on the shelf it went for about twenty years.

Fast forward to the summer of 2022, I decided to build an AM station in the shack and picked up a couple of Rangers that needed work.  One was a parts rig that is now on the air again.  The other one is the early version Ranger that someone later retrofitted with the keyer platform (thatís another story); it is about halfway back to being operable.  Also, I recently found the audio issue with the Valiant, the clipping control was toast, so it is now back among the living!

Iíve looked for a Viking 500 for about four decades, and a nice one recently followed me home and is in my shack! Exterior paint is original with a few minor scratches and chips but pretty good overall. The panel key is missingóreplacement?  It is apparently a kit version and is pretty dusty inside.  It looks to have been a long time since it disturbed the airwaves.

The power supply was packed with rolled up newspaper, so I did open it up at purchase to verify it is the correct supply; the two 3B28ís and two 811Aís were wrapped in newspaper as well.  It looks okay from the top side.

The point here is I am comfortable working inside Johnson transmitters; however, I do realize the Viking 500 is a different animal from Rangers and Valiants--this is why I am posting here on AMfone.   I am hoping folks here who have experience with the Viking 500 will chime in and share their experiences, both good and/or bad and share advice on how to approach this rig.  I need your help to avoid any known or anticipated pitfalls.  I have done nothing to it, no testing nor removed the case.  (Hoping the iron is goodófingers crossed.)

Thank you in advance.
Best 73,
Russ, kw6t

Title: Re: Johnson Viking 500: New owner
Post by: DMOD on January 06, 2023, 11:16:49 PM
You might try the Search function for past threads:

Title: Re: Johnson Viking 500: New owner
Post by: KW6T on January 08, 2023, 09:12:49 PM
Hello DMOD.  I did search the forums and found some good info, especially regarding the modulator.  That is the section of the transmitter that is the most concerning. Still hoping for more responses.   I plan to go over the entire rig starting next week or the following looking for clues, mods, etc. to come up with the game plan to bring it back to life.  I anticipate this project to take several months (or more) before it is actually ready to power up.  I am in no hurry.

Best 73,
Russ. KW6T

Title: Re: Johnson Viking 500: New owner
Post by: w4bfs on January 10, 2023, 10:50:01 AM
hi Russ and welcome to the forum.  your callsign reminded me of Collins rig I worked on while in the USAF - KWT6 - a hf early solid state rx/exciter and tube PA - Cold War era stuff

be sure to check out Tim's (WA1HLR) upgrades for the EFJ 500 - good stuff!

Title: Re: Johnson Viking 500: New owner
Post by: WO4K on January 10, 2023, 10:20:39 PM
A replacement key on-off switch can be found here:

Title: Re: Johnson Viking 500: New owner
Post by: KW6T on January 11, 2023, 07:06:40 PM

Thanks very much, and I am glad to be here.
There are positives and negatives in our old boatanchor designs, and these do give them some character.  I looked at the mods and will keep them in mind.  However, I think there needs to be a specific purpose in mind when modifying these old transmitters.  Certainly, the designers engineered them for a specific purpose, and I feel they were competent in doing the task given the materials available in the day.   Granted, some operators want to expand the range of their audio sections, and thatís fine too.

The Viking 500 is a rare transmitter, and mine is seemingly in good condition.  My plan is to keep its history intact and leave it as standard as possible.   

Thank you.

Title: Re: Johnson Viking 500: New owner
Post by: KW6T on April 24, 2023, 07:56:57 PM
Hello fellow AM enthusiasts.  To wrap up this thread.  

The good news is after going through the 500, it is now up and operating well.  From initial startup, no arcs, sparks or other major issues, and the audio is very clean.  

Three new cables were made from scratch.  Two broken fuse holders, all the pin connectors and the male octal plug on the power supply chassis were replaced.  All the electrolytics and original foil capacitors were replaced.  One bad ceramic HV bypass cap was found.  One minor wiring error was corrected. About ten resistors were significantly out of spec or open.  All controls and switches required lubricating and cleaning as can be expected.  The only bad tubes were one 0D3, and both VFO tubes (0A2 and 6AU6).  The 18K VFO resistor was replaced with a 5 watt, 20K item.

The relay delay mod was done as well as inrush current limiters. (Thank you Rodger and Mike).


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