[AMRadio] 813 Final Problem

John Coleman jc at pctechref.com
Wed Mar 25 16:02:52 EDT 2015

When I ran 813s in a class C final the grid current was about 16 ma per tube
(seems like it was about 150 total bias, leak resistor plus fixed). With
2200 volts I got about 750 watts out with 1KW input.
John, WA5BXO

-----Original Message-----
From: AMRadio [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Paul
Sent: Thursday, March 19, 2015 12:45 PM
To: amradio at mailman.qth.net
Subject: [AMRadio] 813 Final Problem

I am building a 15 meter 2 x 813 class C final. HV is 2200V. With 16mA grid
drive I can comfortably get 400W (and more) out.

Every thing works fine until I insert the Mod transformer secondary in the
HV lead to the PA. NOTHING is connected to the input (audio) side of the
transformer. When I apply rf drive to the PA my High Voltage connectors arc
over. It seems this must be caused by some sort of inductive spike. Any

- Paul  KW7Y

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