Help with my Viking II

[k5kab]

S.  Turn meter to "plt" position and "plate" on. Turn "drive" clockwise until
      Plate current rises to 100 ma. (Works 100%)

T.  Tune "final" toward 100 until plate current dips sharply. (Works 100%)

U.  Turn meter to "grid", and touch up buffer tuning for maximum grid current.
     Advance "drive" until 6 ma of grid current is obtained. Turn meter to "plt".
     (Works 100%)

V.  Proceed to load the antenna or dummy load by advancing the coupling control
     toward higher numbers, retuning the "final" for a dip after each adjustment
     of the coupling control. Continue this procedure, adjusting coupling control
     and retuning final, until a meter reading of approximately 200 ma. is   obtained,  under resonant conditions (final dipped). After step U. The plt is on  or near  200 ma already. Advancing the coupler moves the current up to 205 or 210 with no dip from the final, and  but losses watts on the watt meter.

X.  Turn "fine coupling" toward higher numbers until the ''p1t'' reading rises to
     About 250. Moving the fine gives me about 220-225 plt with no increase in watts . The Viking will only load up properly to about 200ma plt and 65 watts of carrier . Dip the plate current with "final" adjustment again and follow, this procedure until a desired plate current between 250 and 300 ma has been,  reached. If the desired coupling cannot be obtained with the "coupling" '-, setting of step w, turn the "fine coupling" to 0 and advance "coupling" an-" other step (normally not beyond 6 on 40 meters) and readjust "final" and "fine coupling". "Plate” current on CW should not exceed 300 ma.

What could cause this lack of coupling ?  

[WQ9E]

I think the most likely cause is either "soft" final tubes or reduced high voltage due to your 5R4 rectifiers approaching the end of their life.

[W1AEX]

As you indicated, it looks like your lower stages are behaving normally. Does the final tank circuit issue occur on all bands? What position is the coarse coupling control set to during steps S - V? How much off resonance plate current can you pull at this point (V) in the tuning procedure? With good final tubes it should rise up to well above 300ma. If coarse coupling is set to 1 on a lower band such as 160 or 75 meters and you are seeing 200ma with the final dipped at resonance, my first suspicion would be that one of the fixed coupling caps that form the coarse setting assembly has failed. I think that would be the first place I would look. Another thing that can happen is that the plate tuning cap and roller inductor assembly may have slipped. It would have to be way off to cause anything close to what you are seeing. Easy enough to check that both are at their end settings when the tank circuit is dialed to 0 and 100. I have found that when all is well the Vikings run pretty close to the settings portrayed in the manual.

Good luck!

Rob W1AEX

[K9PNP]

Could be any of the above reasons; agreed.  I would first check the plate and screen grid voltages on the 6146's when this occurs vs what they should be.  Easy to do and would rule out that issue early.

[Pete, WA2CWA]

It also would be helpful to indicate the frequency or band you are using and what are you loading into (dummy load, light bulb, antenna, etc.)

[k5kab]

It also would be helpful to indicate the frequency or band you are using and what are you loading into (dummy load, light bulb, antenna, etc.)

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Thanks for all ofthe information so far. I'm loading a dummy load up on 75/80 meter.

[Pete, WA2CWA]

Make sure that the 160 in/out switch is actually in the out position by visually inspecting the actual switch.

On both Viking II's I had (I still have one) in the 80 meter position, rotation of the variable inductor found 2 plate current dips with one more pronounced then the other. The correct one is the one with the lower dial number reading which should also be the one that gives a deeper plate current dip.