[Amps] output of SB220 typical TSPA

[Joe Isabella]

Jim,
That's precisely why I installed the thin teflon insulated wire (22 AWG I think) from the xfmr to the tubes fil pins.  It definitely was a concern!!

Short of running it on a Variac all the time (thus lowering my HV), I chose to go Rich's route and lower the fils V only.

My 3K-A has a multi-tap filament xfmr which I set to the highest line V tap which lowered the fil V down to around 5V as it should be.

Joe, N3JI

----- Original Message ----
From: k7rdx <k7rdx at charter.net>
To: Tom W8JI <w8ji at w8ji.com>; Joe Isabella <n3ji at yahoo.com>; Amps <amps at contesting.com>
Sent: Monday, July 17, 2006 8:30:21 PM
Subject: Re: [Amps] output of SB220 typical                 TSPA

Agreed Tom...My question was why would someone run an amp with that value of
line voltage if he knew the effect it would have on the fils.I do know for a
fact that a lot of the Chinese 3-500z tubes have higher gain than the older
Eimacs...I personally wouldn`t argue over a few hundred watts if I were
using 3-500`s because the guys hearing you won`t know the diffrence
anyway...Isn`t that why we run tubes with "Handles"? 73,Jim..
----- Original Message ----- 
From: "Tom W8JI" <w8ji at w8ji.com>
To: "k7rdx" <k7rdx at charter.net>; "Joe Isabella" <n3ji at yahoo.com>; "Amps"
<amps at contesting.com>
Sent: Monday, July 17, 2006 4:19 PM
Subject: Re: [Amps] output of SB220 typical TSPA


>
> > Joe,what was the filament voltage with that kind of line
> > input? Excessive
> > filament voltage allows more than normal emission with
> > thoriated tungsten
> > fils...At least for a while! 73, Jim K7RDX..
>
> Jim,
>
> A single tube will easily make 1200 watts or more  with
> enough drive at 3000 volts, and you don't have to run the
> filament extra hot to do it.
> There isn't any doubt at all people are seeing 2kW or more
> from a pair when they bang them with 150 watts or more at
> 3kV or more.
>
> The problem is with claims that a pair in g-g run 1500 watts
> or more out with 100 watts of drive and about 3kV on the
> anode. It really won't happen, even if you put 10 volts on
> the filament. The problem is power gain, and the gain is
> largely set by the ratio of cathode driving impedance to
> anode load impedance in a g-g amp. The only way to get more
> gain is by running more HV so the anode impedance is higher.
>
> 73 Tom
>