[Boatanchors] Viking II

[telegrapher at q.com]

Here's a new one to me anyway.

I pulled the Viking II off the shelf with the intent of replacing some of the caps as well as the bias resistor, R-13.  Well got that all done ok.  While the bottom is off i have to set the R-13 for correct mod bias etc so might as well take care of that. Hooked up cable to Bird Watmeter and then to Commercial 300W dummy load for further testing.  

Mod bias set for 70 ma resting current which is within limits. Pa Resting current about 20 ma.  

Remember i only changed 4 caps in the audio circuitry and nothing else.

Plugged in a key and set CW-Phone switch to CW position.  As the meter switch contacts appear to be a bit unreliable i had to fiddle with the knob for that to get readings for the different settings.  ANyway everything came up to snuff and just about exactly where the manual says the knobs should be resting for 40 meter tuneup.  Now on to the grid and Plate.  I find that before applying plate voltage i can get a good grid current reading of 8 ma then ;it should reduce to around 6 ma when plate voltage is applied or the transmitter is tuned to resonance.  However, in my case i get no grid current reading at all, i can peak the plate I with the grid tuning but can't see any grid current on the meter.  Ok know about that.  go thru the tuneup procedures for 40M.  Can't get near enough Plate current although, although i can run the output up to several hundred watts whcih should not be possible with a pair of 6146 tubes.  No reflected power on the Bird but lots of forward power and Ip is about 130 ma.  Both final tubes are lit up fine with no discoloration.  Amazing, i can vary the power output from nothing to 200+ watts with the drive control.  Now i know that's not right.  Btw, Ip never seems to go above the 130Ma even though power output goes up.  Sounds like a dead or bad 6146?  Maybe the shunt resistor no good.  NAH.  None of the above.  Changed out the 6146's and even switched tubes in the sockets.  NADA.  no change.  Maybe i've come up with a method of genrating phantom RF?  I've looked at this, done measurements, B+ is 620V under load, low B+ is 320 V under load.  All tubes verified to be in their correct sockets and good.  The no reading of grid current when in transmit mode has been a part of this transmitter ever since i got it back in the late 80's.  There is a workaround for that when i run the transmitter so right now it's not a concern.  

Nothing makes sense so i'm kind of stumped.  I wouldn't think since i get a good resonant dip in plate current, although it's only half of what it should be that there would be a neutralization problem.  

Be nice to get this thing fixed and off the center kitchen island before.........

Larry
W0OGH