This is a requirement that is specific to oxide coated cathodes such
as the
YC-156. Read your tube's data sheet for information like this.
Thoriated
cathodes generally heat more quickly than oxide coated cathodes. Most
commercial amplifiers use tubes with thoriated cathodes. Some
small amount of current must flow in the cathode to bias it to cut-off
if
it is cathode switched -- so for oxide coated cathodes why not be
safe?
----- Original Message -----
From: "Bill Turner" <dezrat1242@ispwest.com>
To: "AMPS" <amps@contesting.com>
Sent: Friday, September 17, 2004 7:35 AM
Subject: Re: [Amps] input matching question on the YC156?
> On Thu, 16 Sep 2004 21:54:56 -0700, Leigh S. Jones wrote:
>
> >rule 1: never apply plate voltage to the tube nor apply drive power
> >until after the prescribed filament warm-up period has elapsed
>
> _________________________________________________________
>
> Is this true even when the tube is biased into cutoff? I've owned
> four commercially-made amps and all of them apply HV as soon as the
> power switch is turned on, but all four have the tube biased into
> cutoff. Are you saying that is a design error?
>
> --
> Bill W6WRT
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|