[Johnson] Viking Desk Modulation

Ed Wirtz ewirtz at hbci.com
Mon Jan 14 17:25:17 EST 2008


Hi, Tom,

What's the modulator idling current? It should be around 50 ma. and should 
run up to 100 on low power and 200 on high power and it should do that 
easily. If not, and the idling current is normal, I would check the driver 
which I assume is a Ranger..
----- Original Message ----- 
From: "Tom Elmore" <tom at telmore.com>
To: <Johnson at mailman.qth.net>
Sent: Monday, January 14, 2008 3:27 PM
Subject: [Johnson] Viking Desk Modulation


Hello All, I recently inherited a Viking Desk Kilowatt from a SK friend of 
mine. I returned it to service after almost a year. It seems to make output 
power 275 low power and +700 watts high power. When looking at the 
modulation on a scope though it appears to be only modulating about 80% in 
either low or high power.
I have changed out the 810's and 4-400 and see little improvement. I do 
notice that when I approach 80% modulation on the scope that both positive 
and negative peaks appear to curl slightly instead of going flat like I 
thought I would see with clipping.  Anyone have any thoughts or experience 
on where to look next ?




-Tom / KA1NVZ
Anchorage, Alaska
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