viking II 6146w oscillation

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KB8OSB:
 Hello all. Recently started messing with a v2 I had gotten from my elmer a few years ago. To make a long long (long) story short, it had no finals so I installed a set of jan phillips 6146w's a friend picked up for me at dayton. It makes good power but the plate tuning is funny and it oscillates above the band even with the 122 vfo disconnected. It doesnt seem that the v2 has a neutralization circuit so I dont know if I should add one or just junk the w's and try to find some a's. Thanks in advance for any advice.

WQ9E:
One of my Viking II transmitters is running W suffix finals and the other has B suffix and both are stable so I doubt if the W suffix tubes are causing your problem.  What is the history on the transmitter, do you know why it was missing its finals?  I suspect it had an issue no matter what finals were in there.

A poor ground from corrosion or loose hardware in the final section is a possible cause of this instability so check all of the grounds in the final area.  I just repaired a Valiant that had apparent low output because of the meter reading far more than the actual current.  In this case it was a factory unit and the metering shunts were fine but the connection point for the shunt ground was a riveted connection which had developed some resistance. 

Examine L-6 and L-7 carefully for any signs of damage, I have run into unusual tuning issues in rigs where a choke was damaged due to previous flashover.  Are the final screen bypass caps in good condition?

Make sure the clamper tube circuit is adjusted properly and then pull V5 to determine whether the problem is with the final or earlier in the RF chain.

Hundreds of Viking IIs are still in use and it should operate normally without the need for added circuitry once you identify and correct whatever is causing the current issue. 

KB8OSB:
Well I checked all that stuff. The finals were missing bc my elmer only had one set of tubes to share on several pieces of equipment hihi. So anyway when I pulled v5, it stopped. No buffer, grid, plate or oscillator indication which is what I'd expect. So I guess this means the trouble is in the oscillator? I never really knew a terribly great deal about boat anchors even though they were my main rigs for years. Something blows up, find the short. When it got goofy, off to Mike's house we go ;D

WQ9E:
Sounds like the trouble is in the exciter chain, one of the tubes must be taking off on its on.  I can't remember if there are supposed to be shields on those tubes (V5 and V6)  but check for missing shields, the manual and photos should show whether they have shields.  Also check the bias voltage, a bad filter cap in the bias supply creates lots of issues.

You could try plugging V5 back in and pulling V6, this MAY help you narrow it down to a single stage.

KB8OSB:
Ya know, as I check and recheck things, the clamper circuit doesnt seem to be working. R30 fully clockwise the plate current is 100ma. Dont think that has anything to do with it but I'll swap in another 6aq5 in the morning. Everything is too hot to touch. Thanks fer ur advice om. I'll see if I can get the clamper working and move on along... :-\

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