[Boatanchors] 8122 Suitability/Selection (was: 6146 discussion on )

[D C *Mac* Macdonald]

Thanks, Carl, for that info.
 
I would be driving with a 100 Watt output rig. The 
passive 50 Ohm input circuit of the NCL-2000 is
just one of its many attractions, especially with
fixed impedance output circuits of current ham
transmitters/transceivers.
 
I wonder if there is some source for deciphering
the "color coding" used by Burle for the 8122s.
 
73 - Mac, K2GKK
 
 


----------------------------------------
> From: km1h at jeremy.mv.com
> To: k2gkk at hotmail.com; boatanchors at mailman.qth.net
> Subject: Re: [Boatanchors] 8122 Suitability/Selection (was: 6146 discussion on )
> Date: Wed, 6 Jul 2011 14:35:30 -0400
>
> Every Burle and most any other 8122 Ive used in an NCL-2000 works without
> any modifications as it has a roughly -25 to -42V bias adjustment range. I
> have used a few Eimac 8122W's over the decades and had to modify the range
> adjust by using a different reference zener, these tubes were in the -44
> to -46V range. Modifying for individual bias pots allows using tubes that
> are not a true matched pair, about a 3-4V delta has no measurable effect on
> IMD. This is for 125ma idle current per tube in the SSB position.
>
> The more positive the bias (towards the -25 side) the easier they are to
> drive so consider that if you have drive to burn and consider a higher
> number bias tube.
>
> Since the NCL is swamped grid input there is no neutralization circuit.
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "D C *Mac* Macdonald" <k2gkk at hotmail.com>
> To: <james.liles at comcast.net>; <boatanchors at mailman.qth.net>
> Sent: Wednesday, July 06, 2011 1:52 PM
> Subject: [Boatanchors] 8122 Suitability/Selection (was: 6146 discussion on )
>
>
> >
> > Hi, Jim (and others).
> >
> > Might I ask how Burle 8122s can be correctly
> > chosen for use in the National NCL-2000 amp?
> >
> > I have previously been advised that original
> > NOS RCAs are no longer available at decent cost.
> >
> > * * * * * * * * * * *
> > * 73 - Mac, K2GKK/5 *
> > * (Since 30 Nov 53) *
> > * Oklahoma City, OK *
> > * USAF, Ret (61-81) *
> > * * * * * * * * * * *
> >
> >
> >
> >
> > From: james.liles at comcast.net
> > To: boatanchors at mailman.qth.net
> > Date: Wed, 6 Jul 2011 12:36:29 -0500
> > Subject: [Boatanchors] 6146 vs 6146A vs 6146B or 6146W
> >
> > > SNIPPAGE <
> >
> > The reason that I followed with interest is the history of the 8122 seems
> > to
> > draw a parallel. Some amplifiers will work with any 8122 and others will
> > only work with about 3/4 of the production without modification, and
> > others
> > cannot be made to operate properly with nearly 1 in 6 8122's. There is a
> > broad range of bias and neutralization attributes involved. Burle is the
> > only manufacturer that classified them with a four color code to enable
> > intelligent choice.
> >
> > Kindest regards Jim K9AXN