[Boatanchors] Viking II

[Carl]

----- Original Message ----- 
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: <telegrapher at q.com>; <boatanchors at mailman.qth.net>
Sent: Monday, July 04, 2011 1:32 PM
Subject: Re: [Boatanchors] Viking II


>
> ----- Original Message ----- 
> From: <telegrapher at q.com>
> To: <boatanchors at mailman.qth.net>
> Sent: Monday, July 04, 2011 8:53 AM
> Subject: [Boatanchors] Viking II
>
>
>> 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 an
>> d 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
>
>    All I can suggest is to make sure your measuring
> instruments, including those in the transmitter, are giving
> you reliable measurements. The flakey switch bothers me. See
> if you can get it to be more stable. I suggest cleaning it
> with Deoxit and polishing the rotor contacts with the Deoxit
> and a soft wooden stick, a kitchen match or those sticks
> sold for cleaning teeth should do. Also check the switch
> contacts, sometimes they get loose. Sometimes that can be
> fixed by simply pushing on the with the stick.
>    Also, check the actual impedance of your dummy load, it
> may no longer be 50 ohms. Most of these loads are DC coupled
> to the connector so a simple ohmeter measurment should do.
>    If you have an RF vtvm you can check the Bird readings
> by measuring the voltage across the dummy load (after making
> sure of the load impedance).
>    As much as possible I would check the various currents
> and voltages with an independant meter.
>    Also, although it seems far fetched, if the TX has a
> neutralizing cap make sure its neutralized.
>    I can't think of much else but stress to always check
> your instruments especially if they are giving you
> impossible readings.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com



The Viking II is self neutralized and there is no way you will get more than 
about 180W INPUT out of it.

The first suspect is the power meter and load especially if it is MFJ.

>From there Id recheck the wiring that you did in the rig. I have a Vik II 
CDC model on the bench and may be able to help you with some of it except 
for the audio where there are differences via factory added circuitry.

Carl
KM1H