Johnson Navigator chirps....

Discussion in '"Boat Anchor" & Classic Equipment' started by K1ZJH, Nov 27, 2018.

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  1. K1ZJH

    K1ZJH Ham Member QRZ Page

    I've finally have the Navigator on the air and mated with my SX-101A and HT-32 station.

    Unfortunately, I noticed the beast has a chirp on CW. I am aware of the issue on 40 meters where the VFO enclosure screws need to be checked for tightness. That did not fix it.

    The gas regulator tube was changed out. B+ does drop a bit on keydown, but it seems to be in spec according to manual. Is this normal for the rig? I'd expect the Navigator to be rock solid on 80 or 40 CW.

    Pete
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I never had a Navigator, but have read about this and the "fix" involved more than just tightening the screws. Sounds like the covers (shields, plates, whatever) need to be removed and thoroughly cleaned at mating surfaces prior to screw tightening, to help assure an actual "RF" seal of mating surfaces.

    Found this writeup:
     
  3. N2EY

    N2EY Premium Subscriber QRZ Page

    It should be at least as good as a Ranger.


    The Navigator uses "time sequence keying" (aka differential keying) for chirp suppression. The idea is that as soon as the key is closed, the VFO turns on immediately, but the driver and final stages take a few milliseconds. Any chirp/click is over before the driver and final are fully on. Same as when the key opens.

    Some things to check:

    1) If any of the tubes other than the final are "tired", chirp can be the result.

    2) @K9STH recommends the use of a 6AH6 for the VFO, and is worth a try.

    3) Bias supply could be "tired" as well - filter caps, resistors, etc.

    4) Shields as mentioned, but also grounds and bypasses.

    5) In my experience, VR tubes can have very variable characteristics - and ordinary tube testers don't test them well. Years ago I haywired together a VR tube tester (very simple) which saved me a lot of trouble.

    6) Does it chirp with the final screen grounded?

    73 de Jim, N2EY
     
  4. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    ZJH:

    Unfortunately, the VR-150 also regulates the screen voltage of the 6146. The "fix" for the Heath VF-1, Johnson 122, and the VFOs in the Ranger series and Valiant series involves replacing the 6AU6 with a 6AH6 and replacing the screen regulator 0A2 with an 0B2. This reduces the screen voltage on the oscillator to 108 VDC regulated and this helps tame the "chirp" as well as the 6AH6 being less likely to chirp and drift.

    If the transmitter were mine, I would break the line from the VR-150 that goes to the screen of the oscillator tube. Then, add a 7-pin miniature tube socket on a small bracket under the chassis. Connect the wire that goes to the oscillator screen to pin-5 of the added socket and then a 15K-ohm 5-watt (or 10-watt) resistor to the junction of R-21 and C-24. Connect pin-7 to chassis ground. Then, install an 0B2 in the added socket. This will lower the screen voltage on the oscillator tube as well as isolating the oscillator tube from the final amplifier screen.

    Glen, K9STH
     
    W1TRY likes this.
  5. K1ZJH

    K1ZJH Ham Member QRZ Page

    Glen

    I am tempted to add a Zener on the oscillator screen, and drop the voltage from the 0D3. The B Plus variation between key up and key down is a bit more than I'd like to see. While the minimum B+ is what the manual states, the unkeyed voltage is higher.

    At this point I am going to order a few 6AH6 tubes and a new 6CL6 to see what happens. I'm also tempted to use the HV variable/regulated bench supply to substitute voltages in a few areas next time it is on the bench. Removing over twenty screws to get inside the cabinet is a bit tiring.
     
  6. N2EY

    N2EY Premium Subscriber QRZ Page

    I wouldn't go changing things in the Navigator so quickly.

    I've tested 0D3s that don't move the width of the multimeter needle from 5 to 40 mA. If you're seeing significant changes from key up to key down, I'd check into the power supply, regulator tube, etc., FIRST. Also check current through the 0D3, if it's too much or too little, all bets are off.

    In any older rig, the carbon comp resistors are suspect, and the Navigator has lots of them which could be the culprit.

    If you need a tested/good 0D3, let me know...

    73 de Jim, N2EY
     
    KD2ACO and W7UUU like this.
  7. K1ZJH

    K1ZJH Ham Member QRZ Page

    Thanks for the offer Jim. I have several new ones in my stash.. and one was installed in the Navigator. Right now I am concerned about the high voltage shift between load and no load... that is causing quite a variation in the 0D3 idling current. I want to measure the current change across the dropping resistor. As I recall, the 0D3 regulated voltage shifting at least two volts.

    Pete
     
  8. K1ZJH

    K1ZJH Ham Member QRZ Page

    Update:
    It is back on the bench. New tubes will be here by Saturday, and I have some 56 volt 5-watt Zeners on order as well.

    I should correct the comment about the chirp problem--it is more of a "bloop" than a chirp.

    I've talked to a few owners and most of this transmitters do not have a problem, which means something is off with mine. Regulating the 6AU6 screen and plate, as well as the 6CL6 screen seems to produce a very clean note. But, that is masking the problem and not really finding why this particular Navigator is acting up.

    We'll see what a 6AH6 and new driver will do, and also will try several OD3 gas tubes to find the one with the least voltage shift.

    Someone just sold a Navigator the classifieds for 150 bucks! That is about 1/4th the going auction site prices! I hope the buyer uses it.

    Pete
     
  9. K9MOV

    K9MOV Ham Member QRZ Page

    I had the same problem with my Navigator and chased it for 1 month, getting nowhere. I ran across this article on W8JI website. It explains the poor grounding of the plate tuning Cap. and RF feeding back into the vfo housing. The fix is very easy and cured my problem 100%. https://www.w8ji.com/johnson_vfo_chirp_jump.htm
     
    K1ZJH and N2EY like this.
  10. K1ZJH

    K1ZJH Ham Member QRZ Page

    Thanks for that link. That did help a lot with the problem. I still needed to improve the oscillator voltage regulation as well.... but at this point she sounds like she is crystal controlled. I am waiting for the 6AH6 tube to arrive before committing to the added regulated voltage circuit changes. I had two problems, first the VFO was pulling with power supply sag--a blooping sound. That was aggravated by the fact the frequency could be pulled by adjusting the loading control.

    Pete
     

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