EF Johnson Viking 2 variant?

Discussion in '"Boat Anchor" & Classic Equipment' started by N2IQD, Dec 24, 2019.

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  1. N2IQD

    N2IQD Ham Member QRZ Page

    I recently acquired a Viking 2. It looks to be factory built with very fine soldering and the EF Johnson sticker on the chassis inside. I got a good quality manual with good pictures. When I compared there were some differences. There is no R30 or R13. My question is was there a variant which did not have resistor R 30 which is a 1 M ohm pot. There is no sign that it was ever there at all. There appear to be extra fixed resistors in that circuit with L6. All the on line pictures and videos clearly show R30.
    I've been going through the radio and replacing resistors which have values out of tolerance with what is in there now. I replaced the wire wound 20 K slide and fixed resistors with new ones as the old ones had broken and were jerryrigged. I have replaced the electrolytics.
    The serial number is 5491, but I cannot find a way to date it. I suspect it may be an early model.
    Has anyone seen one of these, and if so would you recommend any mods.
    Any suggestions would be appreciated.
    N2IQD
    George
     
  2. W1NB

    W1NB XML Subscriber QRZ Page

    If R13 and R30 are missing then someone has modified the screen voltage regulator circuit. If it were me, I’d start tracing back from the screens of both the 807s and 6146s and diagram everything. It’s likely someone modified it to change the screen voltage source from the HV to the 300v circuit.

    There are several modifications out on the web. Applying them really depends on that you want for a transmitter. If you want enhanced fidelity AM, you’ll want to consider one of the multitude of speech amp upgrade circuits. If you are happy with narrow communications audio, leave it stock. Take a close look at what’s there now. If someone went to the trouble to modify the screen supply it’s likely they did some mods to the speech amp.
     
    N2EY likes this.
  3. N2IQD

    N2IQD Ham Member QRZ Page

    Thanks for the response. I'm sorry, R 13 was jerry rigged not missing, and I replaced it with a proper slide resistor 50 W 20K. R 6 and R 30 are not present, both 1 megaOhm Pots.
    While in my manual R6 is specified in the parts list, I can't find it on the pictured or in the schematic. R 30 on the other hand along with R29 a 470K resistor are not present. There is no perforation in the chassis for R 30 or sign that the wiring harness was altered, so I don't believe it was ever there. I'll try to send a picture.
     
  4. W1NB

    W1NB XML Subscriber QRZ Page

    R6 is the mic gain control located on the bottom right of the radio face. It’s labeled “Audio”. In the schematic, it’s the 1M potentiometer on the grid of the 6AU6.
     
  5. N2IQD

    N2IQD Ham Member QRZ Page

    Thanks again for the response. It turns out that not only is there no R30, But there is no V28 6AQ5. There is no sign that there ever was a "clamper tube".
    I got the radio for 125$ and recapped it and replace a number of resistors. It loads up fine with good output just as the manual says. I have not yet restore the modulation
    section, and have not tried it on AM. Has anyone seen this variation of the viking II? The serial number is 5491, but I can't find production dates to see if this is an early model.
    I'd like to know if that info is available anywhere.
    None of this probably matters. It's working well, and I will eventually see what it does on phone, but I am curious.
     
  6. W1NB

    W1NB XML Subscriber QRZ Page

    The Viking II was available both factory wired and in kit form. It is possible that someone bought the kit and modified it during construction.
     
  7. W4KJG

    W4KJG Subscriber QRZ Page

    I think that all of my old friends who worked in Waseca are now probably long gone. I do know they built small numbers of modified transmitters for special uses in the early to mid 1950s. One that sticks in my mind was the Viking II CDC. I believe it covered 1.8-30 MHz continuous. I think it was built from about 1952 to 1954 in small quantities, maybe a few hundred. It was for Civil Defence use. I was able to find a manual for it, but it has a final amplifier 6AQ5 screen regulator.

    I am fairly certain there were a number of other special models of most of the transmitters. I looked for an archive of E.F. Johnson documentation, but could not find anything special.

    I worked for a number of radio manufacturers during my career where we made many special variations to standard production radios. The serial numbers of the special units were generally encoded as date codes. This is just a guess, but your unit may have been the 91st unit assembled in 1954.

    I would hope that someone else might know of similar units without the 6AQ5 screen regulator. Again. Im just guessing, but if it never had a 6AQ5 screen regulator, it was probably only used for CW.

    If it was a prototype, engineering model, or pre-production unit it would have a lot more similarities between the Viking I and Viking II.

    Good luck. I wish I could be of more help.

    Ken
     
  8. N2EY

    N2EY Premium Subscriber QRZ Page

    In Electric Radio for this month (January 2020) there is an excellent article by AB2RA about the Viking II. She says that early models of the V2 did not have the 6AQ5 clamp tube and had other differences.

    See also her excellent website:

    http://www.wireless-girl.com/
     
  9. N2IQD

    N2IQD Ham Member QRZ Page

    Thanks a lot for the very good info. I did suspect from the serial number that it was likely built in 1954 which is great, makes it a year older than me. I'm pretty sure it was factory made
    as it has the label on the chassis, and the quality of construction is very good. I don't think it was a kit and modified as there are no perforations in the chassis for R30 or V28.
    I am definitely going to read the Electric Radio article.
    Thanks again

    George
     
    N2EY likes this.
  10. KE0ZU

    KE0ZU Ham Member QRZ Page

    The first hint as to whether or not a unit was factory built is to look at the tube socket mounting hardware.

    Screws/washers/nuts=Kit

    Rivets=Factory
     
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