[Johnson] Valiant Output

[John Lawson]

On Thu, 22 Dec 2005, Jim Brannigan wrote:

> The metering resistors tend to drift higher in value.
> These can all be replaced with parts from Mouser or your favorite supply 
> house.
>
> Jim
>
>
>> When I load my Valiant to 450 ma on the meter, I only get 100 watts output. 
>> I've read that its possible that the meter is reading higher than actual 
>> plate current.  Is there a way to calibrate the meter?  Regards, John
>> John D. Littlejohn, W9NET




    Jim has very good info - but I wonder two things: why are you loading 
to 450? This is the 'low-duty-cycle' regime, for CW or SSB. 330 mA is 
generally the final load point for AM.....  also, what is the condition of 
the finals? If they're getting old and soft, especially if they've been 
"blushing" a bit at 450 mA, then possibly that might account for the low 
apparent output.

   Then - are you 'sure' of the calibration of your wattmeter? I had the 
same thing happen - an older tuner I had with a built-in wattmeter gave 
low readings, I went through a lot of needless gyrations until a friend 
brought over his Bird meter and I found my stupid little tuner was just 
about 25 watts 'shy' .

  Take a look at the "big picture" before you tear into the meter shunts - 
might save you some bench time...


   Cheers and Best of the Season!

John  KB6SCO