[Johnson] Fw: Valiant grid drive problem

[Roy Morgan]

At 10:17 PM 11/20/02 -0600, john w. king wrote:

> > Tonite I put three new 6146 W tubes in the final of my Johnson Viking
> > Valiant.
> >
> > 3. The grid current meter goes negative on all bands except 40 and 15.
> >
> > What is happening to my grid current???????

John,

You may have an open current meter shunt.  This is a hunch, not based on an 
actual fault.  I suggest you check all current shunts and if you can, 
arrange a power supply and limiting resistor to inject current into the 
cold transmitter to check both the function and accuracy of the grid 
current meter system.

First, pull the power cord!  (and if it has a fused line cord plug on it, 
replace it NOW with a three wire grounded line cord and one fuse inside the 
radio.)

Pull one RF final tube and make an arrangement to inject some negative 
current into the grid pin.  A low voltage power supply and limiting 
resistor will to the job.  Check the manual for correct full scale 
indication and see if the meter indicates correctly.

While you are at it, check the final cathode current and modulator current, 
too.

One of these meter shunts is a little innocuous piece of thin wire on the 
terminal strip that carries the filament lines to the final tubes.  It may 
be covered with a piece of insulating tubing and be very easy to overlook.

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan@nist.gov --