[Johnson] Valiant 6146 Question

[Dennis A. Deaton]

Scott,

The two variants of 6146's are VERY different. The 6146 and 6146A have
plate dissipations of 25-Watts while the 6146B is rated at 35-Watts.
This combined with variations in mutual conductance and inter-electrode
capacitance make them behave differently. So mixing the variants in any
application is not a good idea. 

The Valiant (both I and II) has very heavy duty components in both the
final pi-network and neutralizing circuits. So it doesn't suffer from
the same problems that people experience with Collins S-Lines and
KWM-2s. So using the 6146Bs and Ws raise no issues. But when you replace
the old 6146s or 6146As with 6146Bs, be sure to do the neutralization
alignment. This is required due to the different mutual conductance and
inter-electrode capacitance values.

Good luck,
Dennis Deaton, WA6ACC
Redlands, CA



On Wed, 2012-12-19 at 11:18 -0500, Carl wrote:
> Ive tried all combinations and as many brands and date codes as I could find 
> in a V II about a year ago out of curiosity. They all worked just fine 
> 160-10M.
> 
> A Valiant will be on the bench early next year and I'll try again.
> 
> Carl
> KM1H
> 
> 
> ----- Original Message ----- 
> From: <whitebear1122 at comcast.net>
> To: <Johnson at mailman.qth.net>
> Cc: <boatanchors at mailman.qth.net>
> Sent: Wednesday, December 19, 2012 10:32 AM
> Subject: [Johnson] Valiant 6146 Question
> 
> 
> >
> >
> >
> > While I've read Glen Zooks 6146 article, and fine article it is too!, I 
> > wonder if anyone here has had any personal expereince with 6146 vs 6146B 
> > vs 6146W mixing and matching in the PA of the Valiant. Over the weekend I 
> > repaired my Valiant and ended up replacing two of the three 6146's in the 
> > PA. They only blew out after I had overstressed the transmitter while 
> > trying to tune up on 160m with an antenna and tuner that just wasn't going 
> > to take me there, so it wasn't the transmitters fault nor the tubes fault. 
> > I was my error. I've since replaced the antenna and it tunes fine on 160m 
> > now. After I closed up the transmitter,I then remembered the 6146 mixing 
> > and matching debate. I had not paid any attention to the 6146 flavors when 
> > put in the replacements. It seems to be working nicely at least on 80m and 
> > 40m. Haven't tried it on 20m yet. 150 watts output on CW. I know I have 
> > 6146W's in the modulator and they work FB.
> >
> >
> >
> > I was just curious if others had actually had problems with the mixing and 
> > matching 6146's in the PA.
> >
> >
> >
> > I am also looking to buy some NOS 6146s, either straight, A's, B's, or 
> > W's. I need some spares now. Out of my 4 spares, two are now in the 
> > Valiant, and the other two turned out to be weak. They read 45 on the TV-7 
> > (where 35 is minimum), but then quickly started dropping to the 20's 
> > before I let off on the button.
> >
> >
> >
> > Thanks. 73, Scott WA9WFA
> > ______________________________________________________________
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