The EBS circuit goes in the cathode/grid path, I.E. cathode
to ground (grid). It is installed from the anode of the bias zener to
ground
(grid) and the B- goes to the junction of the bias zener cathode and the
tube cathode in a cathode driven amp. So in effect, the EBS is in series
with the tubes cathode - grid path.
In the 2 meter amplifier after a 3 minute CW transmission at about 20
wpm
into a dummy load, the average anode exhaust temperature went from 205
degrees F
to just under 100 degrees F when using the EBS. In the 2 meter amp, the
EBS
switches the bias voltage applied to the 4CX250B grid from cutoff to
operating levels,
I don't remember for sure but I think the cutoff voltage is -100 volts
and the operating
is about -45 volts.
Mark WB8JKR
On Sun, 3 Aug 2003 07:43:33 +0100 "Steve Thompson" <g8gsq@qsl.net>
writes:
>
> ----- Original Message -----
> From: <wb8jkr@juno.com>
> To: <nospam4me@juno.com>
> Cc: <amps@contesting.com>
> Sent: 01 August 2003 18:21
> Subject: Re: [Amps] re: EBS at soft or quiet moments
>
>
> > There is a way to clean up EBS circuits, I did it a number of
> > years ago and have never once had comment that the improvement
> > isn't short of spectacular. I have a 4CX250B 2 meter amp I built
> > a number of years ago that uses EBS due to the fact that the tube
> > idles at near full dissipation. I get great reports on the signal
> > even with relatively close in stations, and I can switch the
> > EBS in and out of circuit for comparison.
> > At any rate, all you need to do is install a 5-10 ufd 100-150
> > volt electrolytic capacitor across the bias swtiching transistor.
> > When cathode current begins to flow the charging of the capacitor
> > will provide a path for current flow just long enough for the
> switching
> > transistor to saturate. Sounds simple as hell, but I can tell you
> it
> > works
> > quite well.
> Which supply are you switching with the transistor?
>
> Thanks,
>
> Steve
>
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>
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