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Re: [Amps] Alpha PA77 vs 77Dx plate choke?

To: audioguy@q.com
Subject: Re: [Amps] Alpha PA77 vs 77Dx plate choke?
From: Rob Atkinson <ranchorobbo@gmail.com>
Date: Mon, 18 Jun 2012 22:04:57 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
work up some kind of plastic fork wand thing a few feet long for
holding the IR thermometer close to the choke or just tape it to a
length of PVC.

thanks for the cap information.

73

Rob
K5UJ



On Mon, Jun 18, 2012 at 1:21 PM, Jim Barber <audioguy@q.com> wrote:
> That might be the right question.
>
> Starting at the supply end on the 77Dx:
> From the 15uH molded choke, there's .002uF to ground.
> At the junction of the 15uH and 90uH chokes, there's .005 total to ground.
>
> Again the two chokes are in series, with the 15uH going to the supply and
> the
> 90uH being the "main" choke.
>
> WRT input from Carl & Paul, I think what I'll do in the short term is add
> the additional bypass caps to make it fit the 77Dx schematic, fire it up and
> see what happens. The choke is far enough from the tube to measure temp with
> a non-contact IR gadget, or if I can't get good readings I can borrow a
> thermal imaging camera for a couple of days. ( I secretly lust for one
> anyway, but can't justify ~$2K to buy one) If the chokes or bypass caps get
> hot enough to worry about after a few 300-watt AM transmissions then I can
> consider what to do next.
>
> Thanks to all,
> Jim N7CXI
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