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THE AM BULLETIN BOARD => Technical Forum => Topic started by: k5kab on February 04, 2010, 10:32:22 AM



Title: Johnson Viking Valiant Tune procedures
Post by: k5kab on February 04, 2010, 10:32:22 AM
Can someone help me out?
Purchased a Johnson Viking valiant retubed it and finale got output.
The problem is tuning. Here’s what the manual says to do.

1. Turn to OSC, Buffer for positive current draw.

2. Turn oscillator control to zero turn meter to Grid,  (mode switch to CW) with Driver on 3, peak out meter with the excite and back driver down to 8 ma.    

3.  Turn Aux coupling to 8 and fine to 0.

4.  Key transmitter while tuning final to max wattage.

5.  Turn Aux coupling as well as fine for 430 ma for CW or 350 for AM / also continue back and forth with the final for max wattage.

6.  Clipper on 10, Audio on 6.

7.  Now here is the part that gets me. I would like to tune up for 40 meter or 75 meter AM.

??????????

8.   Turn Oscillator to VFO  select freq and TX ?
9.   This has produced about 40 watts no good ??? on tunning its showing 175 watts .. (what gives) help please.  817-637-9066 or kerryebro@sbcglobal.net


Title: Re: Johnson Viking Vaiant Tune procedures
Post by: Ed/KB1HYS on February 04, 2010, 10:58:45 AM
that sounds about right, you may need to increase the Drive a little bit, I find on my valiant that about 5 works for initial tunning, just keep the Gird Current at or below 8ma.   (momentary excursions ok while tuning). 

I run the loading a little lighter on AM than recommended. helps a little with the modulation. 

If you are not getting a good 100 watts or better out on 40 or so you may have another problem besides tuning.

The meter can be a problem on the valiant. You might not be getting the Grid or Final current indicated.  The shunts are usually the issue. Replaceing them with low value resistors is a fix (two 1 ohms in parrallel for 0.5 ohm shunt).



Title: Re: Johnson Viking Valiant Tune procedures
Post by: k5kab on February 04, 2010, 02:31:40 PM
ed thanks for the reponse, my problem is I can turn the aux fine full clockwise after the tune and peak final for max watt meter output and get 130 watts out, is this exceptable?
 


Title: Re: Johnson Viking Valiant Tune procedures
Post by: WQ9E on February 04, 2010, 02:56:37 PM
Kerrye,

What is your meter indicating for plate current and grid current when you are getting 130 watts output?

On 40 meters into a normal load the auxiliary coupling is normally only on 6 or 7 with the fine coupling only slightly advanced and the aux coupling should be set at a much lower number on 80 and 160.  If you don't have enough grid drive (should be right around 8 mils) then you likely have the coupling set too high to get the desired plate current and your output is falling.

What has been done to the Valiant so far?  Unless the bias filter caps have been replaced you can count on them being bad and it is likely that the B+ and HV caps also need replacing.  After this the modulator bias and clamper control should also be reset.  At the very least, replace the bias caps unless you know that has already been done because a failure here will create plenty of additional issues.  The under sized VR tube dropping resistor in the VFO should also be replaced to prevent future issues.

I am on the way to a meeting but later today I will email you my "standard list" of things to check/replace on a Valiant.

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