Hi Jerome,
Alas & alak, my HB 2x813 amplifier here was also cursed with that dreaded
"Ker-CHUNK!!!" from the robust T/R relay I employed whenever I'd start /
stop transmitting...
This past autumn I adopted a solution that may not be especially "elegant",
but it IS effective: I simply unbolted the relay from its sub-enclosure
(thus severing it from its "echo chamber") and wrapped it in a strip of
sponge / foam...
I actually have to strain my ears now to hear the linear switch over!
Try it, you're sure to like it as an improvement to your current situation.
~73!~ Eddy VE3CUI - VE3XZ
*******************************************
----- Original Message -----
From: "jerome schatten" <romers@shaw.ca>
To: "Chuck Lewis" <n4nm@knology.net>; "Amps" <amps@contesting.com>
Sent: Thursday, June 12, 2008 10:54 AM
Subject: Re: [Amps] 813's shot noise?
> Hi Chuck et al:
>
> After running a few more hours, the noise just stopped, period. It
> appears the hobgoblins hiding within have been routed. Maybe it was
> more boiling away that was needed, maybe some piece of ancient dirt
> got dislodged or maybe it ran out of gas. I guess we will never know.
>
> If the problem should return, I'm armed now with the wisdom of your
> replies. Thank you all!
>
> As regards the bias resistor in the B- lead, I never had any problems
> whosoever over the years with this. Now if I could think of a solid
> state way of switching it in and out instead of my klunky T/R relay...
> Any thoughts on that?
>
> Best,
> jerome VA7VV
>
>
> On Wed, 11 Jun 2008 20:39:02 -0700, Chuck Lewis <n4nm@knology.net>
> wrote:
>
> > This is a timely question for me, too, since I'm considering making
> > a modification to my Drake L-7, deriving cutoff bias from a resistor
> > in the filament side, rather than the existing heat-producing
> > voltage divider in the P.S. which would be disabled (yes, there'll
> > still be a bleeder). The 120 VDC from the divider is currently also
> > used to develop ALC, but my exciter is matched nicely to the amp,
> > and I don't anticipate using ALC...therefore, Jerome's question
> > raises an issue applicable to my planned mod: is there an unintended
> > consequence associated with this approach to cut-off bias???
> > Inquiring minds want to know...
> >
> > Chuck, N4NM
> >
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