[Boatanchors] Diode replacements for 866 tubes, ratings needed?

[Drew P. via Boatanchors]

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On Tue, 11/11/14, boatanchors-request at mailman.qth.net <boatanchors-request at mailman.qth.net> wrote:Message: 2
Date: Mon, 10 Nov 2014 17:05:10 -0900
From: Jim Wiley <jwiley at gci.net>
To: Rick Poole WA1RKT <wa1rkt at comcast.net>,
    boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] Diode replacements for 866 tubes, ratings
    needed?
Message-ID: <54616ED6.1040407 at gci.net>
Content-Type: text/plain; charset=utf-8; format=flowed

Jim Wiley


On 11/10/2014 4:16 PM, Rick Poole WA1RKT wrote:

[snipped]

"The Warrior power supply uses a swinging choke in the center tap lead of the power transformer (I must admit, I haven't seen that kind of "choke-input" filter before).  I'm told that choke-input filters tend to generate impressive back-EMF voltage spikes that the rectifiers need to be able to handle." 

To which Jim Wiley responded:

[snipped]

"If you are worried about back-EMF, which could be caused by rapid
transitions from full load to no load, as when using the amplifier for
CW service, simply put a string of 4 or 5 1000V/3A diodes across the
choke to absorb the energy.  The diodes would be connected in opposition
to the normal rectifier diodes"

The problem with putting diodes across the choke to absorb back EMF is that you NEED the choke to create back EMF to do its job in filtering. The choke would no longer develop an opposing EMF against the rising peaks of the ripple.

Drew