[Johnson] Johnson Valiant - Setting Finals and Modulator Bias

[Robert Lawson]

Larry,

Do us a favor and photocopy the Johnson Bulletin #1 10/58 and send it to the BAMA web site
so that it can be posted for us who need it. I run about 40 mils on the modulators and get
good reports. I'd rather run the resting current a little low on those tubes in my
Valiant. Sure would like to take a looksee at that bulletin.

Good luck with your Valiant. I run mine just about daily. No audio mods in it at all. Just
never use the clipper. I use a D-104 with a fresh crystal element with it.

Regards,

Robert W4RL Pensacola Florida

Larry Knapp wrote:

> To the list......I have been trying to fix up my Valiant...I have gone through
> all the normal checks...setting the final grid voltage (bias), modulator bias,
> clamp, keyer, neutralization....all seem fine & stable; tunes up decent on 40 &
> 20 meters (into a dummy load on CW)...the rig has five 6146's in it...no A, B,
> or W....etc...just plain olde 6146's.  If you look at page 8 of the manual, at
> the bottom it says to set the final amplifier grid voltage at
> -70V....fine.....of course mine no longer has the tapped resistor it's got two
> variable resistor pots in it (R61 & R62 see Johnson  bulletin #1 (10/1958), end
> of page 1 into top of page 2 and the diagram on page 4; hope those needing this
> bulletin have it as I can not scan & attach anything to a reflector eMail; it
> was sent to me in September 2000 by J Lutz, W7LPF/3)...if one takes a look at
> pg 31 of the manual, which is the voltage readings on the tubes, V5, V6, V7 and
> look at pin 5, the grids, it says -70V also...OK, fine...the bulletin and the
> manual (page 8) differ a lot.  -70V measured at the final's grids is not a
> problem...I have lots of room on the variable resistor pot...R62.  Now I'm on
> page 4 of the bulletin...on the lead of R23 into one end of R62, I measure
> -96V.  If I use the bulletin's value (top of page 2 of it), it says to set the
> voltage on the grids of the finals at -52V on the arm of R62....which also
> happens to be the voltage you then measure directly on pin 5 of the grids of
> the 6146 finals.  If I digress one moment....my Heathkit DX-100B, HX-10 (since
> it uses 6146 finals), says to have abt -75V on the finals...the Heathkit DX-40
> says -72.  So the -70V Johnson calls for in the manual (page 8) seems right on.
>  To me there is alot of difference though between -52V and -70V.  Right now the
> finals are set at -52V.  Opinion's?
>
> now further....
>
> Note on page 9 of the manual for setting the modulator bias, it says that the
> bias should read -55V and a static modulator current of 60 ma....OK.  Can
> do...remember I have a pot, R61 (see bulletin page 2 & 4) that controls this.
> Note in paragraph 3 & 4 of the bulletin, page 2, it says to set the modulator
> bias at 40 ma, not 60ma.  The bulletin does not specifically say what voltage
> to set the modulator bias at....but if I set it to 40 ma (using R61), at 40 ma
> of modulator bias (read on the Valiant's meter) I get a voltage on pin 5 of the
> modulators of -59V.  It's pretty close to the manual page 9.  So setting the
> modulator bias is pretty close from the bulletin or the manual. Still there is
> a difference.  Opinion's?
>
> =====
> May your days be full of sunshine and good thoughts fill your head.
> From: Larry Knapp, KC8JX, St. Joseph, Mi  49085
>   Best 73's
>
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