[Johnson] Viking 2 Modulation Transformer

[W5HTW at att.net]

I would guess you mean you can't get 250 ma modulator current with a tone injected into the microphone jack.  I am not familiar with the "ER modifications" and probably should become so. The only mod on my Viking II is a PTT one.  

On my Viking II I get exactly what the manual says, 125 ma on voice PEAKS, (averaging 80-110 ma on normal voice) but if I inject a 800 hertz tone without changing settings, I can easily get to 240 ma modulator current with the gain setting at just under 4.  It doesn't look really clean on the scope however at that level.  I can increase the microphone gain and get beyond 250 ma at a setting of just over 5.  In voice operation, I'm using a 'formerly amplified but no longer" D-104 (I don't like amplified microphones!) and a gain setting of 4.    

However, I do not load my II to the maximum suggested ratings, due to the higher line voltages of today.  Under load, the plate voltage on mine is 720 volts, instead of the 600-660 quoted in the manual.  By loading to 300 ma plate current, I get over 135 watts output on CW, and 250 ma gets me 125 watts output, for AM.  However, I run mine at 100 watts output on AM and 110 watts output on CW, or 230 and 250 ma respectively.  

At those ratings, 100 percent modulation, shown on the scope,  with the 800 hertz tone is 220 ma.  And that givee me the 125 ma voice peaks during conversation.  

I agree with others; capacitors in the early audio stages may be a problem.  I had to change some of mine, plus I had a weak tube.  Also, I would guess you are sure your 807s are OK.  If voltage checks on speech amp and modulators are within range, and are adjusted for the 10 percent line voltage increase (from 110 to 125 typically) then the next step is with a scope, to check gain in the stages.  

Have fun.  

Ed


--
Ed Brooks, W5HTW
http://w5htw.home.att.net/index.html
Active since June 1956 Extra since
Jan 1970

 -------------- Original message ----------------------
From: "Bill Stewart" <bstewart at ipass.net>
> Mike, I had a similar problem with my V2....had to turn the audio almost all 
> the way up to get much modulation. I replaced all the caps in the first two 
> audio stages (6AU6's). Now have plenty of modulation. Good luck...Bill K4JYS
>  ----- Original Message ----- 
> From: "w6we" <w6we at charter.net>
> To: <johnson at mailman.qth.net>
> Sent: Wednesday, February 02, 2005 10:01 PM
> Subject: [Johnson] Viking 2 Modulation Transformer
> 
> 
> Gents, How can I determine is the modulation transformer is still in good 
> condition? My problem is I cannot modulate to the suggested 250 Ma , getting 
> no more than 125Ma. I seem to have all the gain I need in the preamp stages. 
> When acquired the audio mods from ER had been installed but not the 
> regulated screen supply or the fixed bias on the 807's. All- in-All, it 
> works but just barely. need to reduce the final input to 80w or so to fully 
> modulate with mic gain fully open.
> Any and all input will be appreciated.( This is my first input to the forum)
> Mike W6WE AMI #1526
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