[AMRadio] Questions on Johnson Ranger II

[Geoff]

On 4/28/2012 4:58 PM, kc9cdt at aol.com wrote:
> Helo fellow AM enthusiasts,
> I just picked up a old Johnson Ranger II.
> Looks completely original, as far as I can tell.
> Even all the caps look original! Hard to believe.
>
> So,
> 1) The VFO bezel has a 1/8" dia paint spot missing and I would like to
> either get a different one, have this painted, or fix it my self....any
> suggestions?
> The front panel is excellent except for this one area.

I, for one, am not big on cosmetics.  I can't help you with in this 
area, but there are several knowledgeable folk on this list that are 
well versed in the subject of paint matching and cosmetic restoration of 
old Johnson rigs.


> 2) Brought it up over 8 hours on a Variac and nothing bad happened
> (even though I did hear 1 little arc). It is now at 115VAC. I do plan
> to put a 3 wire cord on it and fuse.

Good steps.


> 3) Followed the steps in the book to tune up...20 watts out on 80, and
> 12 out on 40??
> a) plate voltage is around 600. Grid drive set at 2 ma.
> b) dummy load
> c) key down

Where's the screen voltage?
a 6146 in a Ranger takes about 2.5mA of grid drive. 250~270v on the 
screen, 500~600v on the plate for ~110mA of plate current.  60 to 65w DC 
input is about all you'll see out of that right, with probably 35~40w of 
carrier output.


> 4) When I checked modulation current it went all the way over to the
> right... I see a step to adj. that in the book, but wander why it is so
> far off?

Sad to say, but it sounds like the modulation transformer primary might 
be open.  Current would swing wildly with no load on the tubes.
Hammon (the organ people) have a transformer that works well in that 
situation and won't cost you an arm and a leg.  Sorry, I don't remember 
the model number of it, right off.


> 5) I find the manual a little lacking..what is the plate voltage right
> on the plate cap supposed to be?

Probably somewhere right around 500~600v.

The little Rangers were called the 'Magic Box' because it was hard to 
believe that all that signal and audio could come out of such a small 
box.  The 7027's are getting hard to find, but 6L6's will work, in a pinch.

The ultra high modulator current concerns me.  Adjusting the sliding-tap 
resistor sets the screen current, and therefore affects the bias of the 
modulators.  As I recall, that should be somewhere around 40~50mA.  The 
interstage modulator driving transformer was the weak spot in the 
Rangers, as well as Viking II's.

Good luck on the project
73 = Best Regards,
-Geoff/W5OMR