Viking Valiant special cap

[N2LK]

Hello- New guy here and working on bringing back to life a Johnson Viking Valiant transmitter. I have a question on this special Cap in the rig, its a 300/600/1200 pf cap I believe. I have cleaned it a bit and its appears pretty corroded but just wanted the experts opinion if this looks usable or just swap out for an arrangment of new caps?

Any guidance appreciated.
73
N2LK

[W3GMS]

Mr. N2LK,

Its impossible to tell if that cap assembly is bad by looking at it.  I would put a capacitance meter on it and read its value. 

The loading caps in the Valiant's are very problematic so it may be good to think about replacing them.  Transmitting Door-knobs type of caps are a good choice as a replacement.  Others have had good luck with the higher voltage mica type of caps.  They are in the 50 ohm part of the pi-network so no extreme HV at that point unlike that of the tuning cap which does have some very high voltage on it.     
Joe-W3GMS

[N1BCG]

That capacitor is a common failure point in Valiants but yours might be fine. Try loading to a known good dummy load on 160 meters. Doing that utilizes all of the caps in that "turnstile" cap assembly. If it seems like you can't dip the current sufficiently even with the AUX knob at "0" then at least one of the caps is bad.

You can also test the output tuning circuit with the Valiant off if you have a 2k Ohm resistor and an antenna analyzer.  Connect the resistor between the plate connection of the 6146 RF tubes and the chassis, then connect the analyzer to the antenna connector. Set the analyzer to 1900 kHz (160M) and tune the Valiant as if it were transmitting (be sure it is off!). Watch the analyzer for a 50Z match with no reactance. Try this on several bands.

The output tuning circuit is simply for impedance matching from about 2k (the plate circuit) to 50 Ohms (the antenna output). Since it works both ways you can reverse the process.

Be sure to remove the resistor when done!

[N2LK]

Thank you fellows, the inputs are much appreciated.
73
John-N2LK

[N8ETQ]

look here..


http://amfone.net/Amforum/index.php?topic=40462.msg295608#msg295608

GL  John

/Dan

[N3GTE]

Hi John and welcome,
Just as a side note you may want to replace the 8 (two groups of four) padding cap used on 80 and 40mtrs at the plate tuning condenser. Best i remember there are 4-350mmf @ 500v connected in series/parallel to create 350mmfd@1kv. This for the 80mtr band on 40 it has a similar setup just a smaller capacitance. At 1kv these caps are way under rated for this application. Need to be about 1.8kv or better. Replaced these postage stamp guy twice before finding some 5kv doorknobs that worked great.

GL
Terry N3GTE

[N2LK]

Thanks Terry...unfortunately I have matching 500V caps coming to replace the old pairs 
Oh well, live and learn

New question (you will be hearing from me alot as I plod thru this project!):

How do you setup the bandswitch cam, that 2 prong thing on shaft and the front dial setting.
the Cam switch is fine, i am just not seeing how to align all these up right??

see photo
73
John-N2LK

[Pete, WA2CWA]

How do you setup the bandswitch cam, that 2 prong thing on shaft and the front dial setting.
the Cam switch is fine, i am just not seeing how to align all these up right??

see photo
73
John-N2LK

Page 5, Step 13 and Figure R of the Valiant Assembly manual provides the step by step information on aligning the VFO cam to the bandswitch.

[N2LK]

Thanks, unfortunately I am having a devil of a time finding the assembly manual for this.
The operating manual is easy but doesnt go into that level of detail on assemblies.

Any recommended source would be appreciated.
73
John-N2LK

[N1BCG]

This is going to require some visualization...

The bandswitch also actuates a three position switch within the VFO enclosure. The three settings are: 1) 160 & 80M, 2) 40, 20, 15, & 10M, 3) 11M

Basically, the cam should advance the shaft to the VFO when you switch between 80 and 40 meters, then again when you switch between 10 and 11 meters. Be sure there is grease on the sloped slots on the cam to minimize friction as the two pins on the bandswitch actuator slide through and advance the cam.

Sure would be easier with a video... :-/

[KB2WIG]

I'd BAMA the Ranger manual -------  Looks like the same set up.


klc


http://bama.edebris.com/manuals/

[N2LK]

The BAMA Ranger pages for these D2/D1 cams hits the nail on the head!
thanks
73
John-N2LK