[Amps] Blowing out finals on a Icom 7300 using a Ameritron AL80B. Help Please!

[jim.thom jim.thom@telus.net]

Date: Tue, 07 Jun 2022 18:43:13 -0500
From: donroden at hiwaay.net
To: Amps Amps <amps at contesting.com>
Subject: Re: [Amps] Blowing out finals on a Icom 7300 using a
        Ameritron AL80B. Help Please!

<how bout an RF Choke .... internal or external to the input to the amp ?
  <   W4DNR

##  On paper, that should work.  Wired between one cathode  lug..and
chassis.
I would be real careful using those small pi wound chokes, like typ used
across a load cap. Ever had a plate block cap short ?   The pi safety choke
explodes.

## what works better is a torroid, wound with   12-18 ga magnet wire.
 50-100 uh is ample, with no series resonances between  160-10m. This works
good across a load cap.  It would/should also work between cathode to
chassis But it would also be effectively in parallel with the bifilar fil
choke too.  GDT's would be a cheap and effective method.

## too bad the chinese don't know how to build a tube.  perhaps what's
needed, is to hi pot test between anode and cathode.  It should be sky
high.  A good  3-500Z should hi-pot test to 15-16 kv, between anode to
grid.  And several kv from grid to cathode.

Jim   VE7RF