[ARC5] Why "Noodling" About Sweep Tubes

Fri Oct 25 21:14:07 EDT 2013

I entered "tube 813 triode connect" into the search box and got a bunch of results, including this bit of tid;

>From The AM Window website (www.amfone.org)
Re: 813's as triodes
Posted by Bill Kleronomos, KD0HG on November 12, 2000 at
23:09:44:

The specs for triode connected 813s are :

Max Ep= 2500, P-P load =~15,000, power out = 550W.
Depending on the plate voltage, you'll need a few volts of
bias which can be provided in the conventional manner.  The
u of a triode-connected 813 is 8.5.

The exact P-P load Z and match isn't anywhere as important
as the turns ratio between your mod transformer windings.

To triode connect, tie G1 and G2 together and treat as one
control grid. You can ground G3 and the internal shield.

Look for a mod transformer (and any associated reactor)out
of a 250-1000 watt broadcast transmitter, for starters. The
iron out of a BC-610 or a T-368 would also be useable, but
not quite as hi-fi at full power.

A good resource for broadcast transmitter parts and
contacting people that might have good junque is
www.broadcast.net and
http://radio-classifieds.com/classpro/viewads.html

luck

Bill
Berthoud, Colo.

and another;

Matt,
        There are many variations of triode connected tetrodes.
 I have seen a few strange ones over the years. There are 2 common 
approaches. For LOW POWER class A audio G2 is usually tied to the plate.

For HIGH POWERED class B audio or RF service G1 and G2 are tied together and driven as the control grid.
In
 Grounded grid RF service even though both grids are grounded and the 
drive is applied to the cathode, the circuit is still a triode 
connection. (as long as the incoming signal to be amplified is fed 
between the cathode and grid it doesnt matter if the grid id grounded or
 floating)

The most commom application for 813's is either grounded grid as a leenyour amp. Or as Class B modulators
As
 class B modders both grids are tied together and fed the incoming 
audio. Tom's "tesla 360" transmitter in the above post is a real good 
example if you want to use them for audio.

> Date: Fri, 25 Oct 2013 10:49:45 -0700
> From: ianmwilson73 at gmail.com
> To: wlfuqu00 at uky.edu
> CC: arc5 at mailman.qth.net
> Subject: Re: [ARC5] Why "Noodling" About Sweep Tubes
> 
> Someone mentioned the 813 - seems like a useful possibility, since
> it has the right filament voltage, plate dissipation, and will stand off
> a few kV no problem.
> 
> No idea what the triode characteristics would be like.
> 
> 813's aren't particularly cheap, but they are much cheaper than 211s.
> 
> 803's are another possibility but perhaps getting too bulky to package
> this up and fit into the original location.
> 
> 73, ian K3IMW
> 
> 
> 
> On Wed, Oct 23, 2013 at 4:56 PM, Fuqua, Bill L <wlfuqu00 at uky.edu> wrote:
> 
> >     Depending on the version of 211 you are replacing. They have plate
> > dissipation ratings  from 75 to 125 watts.
> > Well over nearly 3 to 5 times that of a 807 or 1625. Also, over twice
> >  that of 6146.
> >    Triode connected 807, 1625 or 6146 tubes would behave like zero bias
> > triodes also. So in all cases the bias
> > would have to be quite different as drive requirements.
> >    My email was not only for those looking for a substitute for 211 tubes
> > but for those looking into using
> > horizontal output tubes for projects.
> >   73
> > Bill wa4lav
> >
> >
> > ________________________________________
> > From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on
> > behalf of Kenneth G. Gordon [kgordon2006 at frontier.com]
> > Sent: Wednesday, October 23, 2013 2:05 PM
> > To: ARC-5 List
> > Subject: Re: [ARC5] Why "Noodling" About Sweep Tubes
> >
> > On 22 Oct 2013 at 18:24, Fuqua, Bill L wrote:
> >
> > >   One other thing, when using these tubes you are allowed to let the
> > >   plate glow.
> >
> > Well, yes, but in some cases, like with many of the Eimac tubes, plate
> > "glow"
> > is REQUIRED in order to promote "gettering". Those tubes with thin,
> > tantalum plates are especially designed for that express purpose.
> >
> > > Looks great in an amplifier.
> >
> > I heartily agree! :-)
> >
> > >    If you use a 4-125A
> >
> > which is also the same tube as the 4D21 and 6155.
> >
> > > you can later on upgrade to 4-250A, 4-400A or
> > >    3-500z
> >
> > All of which are required to show considerable color on the plate...again
> > to
> > promote and preserve "gettering".
> >
> > > (if G-G amp) by
> > > using larger filament transformer and higher current power supply.
> >
> > Yes.
> >
> > > You
> > > may have to change the input and output ckts depending on design.
> >
> > Due to the differences in plate impedances caused by the differences in
> > voltage and current.
> >
> > > If
> > > you use continuously variable designs using roller inductors and they
> > > are conservatively rated no change needed . Sockets are all the same.
> >
> > Yup.
> >
> > However, for what Dave wants to do, I think triode-connected 6146 family
> > tubes would be quite good enough...or even 807s or 1625s or 5933s. They
> > are all about the same tube anyway.
> >
> > Ken W7EKB
> > ______________________________________________________________
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