[ARC5] Why "Noodling" About Sweep Tubes

[Kenneth G. Gordon]

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