[Johnson] Valiant Grid Drive Problem

[Ed Wirtz]

Harry,

My Valiant manual states that the RF bias should be set at -52 volts. The 
remaining bias to achieve class C operation is provided by the buffer/ 
multiplier as grid leak bias with normal excitation. The -52 volts is 
actually safety bias and is really more important when the Valiant is 
operated on SSB with an external exciter. I wouldn't worry about setting the 
bias at -35 volts as long as the clamper is working and is set properly 
according to the manual.

73,

Ed, KØBKA
----- Original Message ----- 
From: "Harry Williams" <willisw200 at msn.com>
To: "johnson" <Johnson at mailman.qth.net>
Sent: Thursday, January 03, 2008 12:15 PM
Subject: [Johnson] Valiant Grid Drive Problem


My Valiant has adequate grid drive through 40M. On 20 I have to run the 
drive control wide open to get 8 MA. On 15 and 10 I can not get enough. I 
have checked the tubes and replaced the 5763 as it showed an intermittent 
short cathode to filament but that did not fix the low drive issue. I 
checked the bias on the 6146's and it was
-70V as the manual specifies. Just for the heck of it I turned this back 
to -35V and my grid drive immediately came up to more normal levels. So 
first question is am I just compensating for another issue by doing this 
which is what I am thinking is the case. After reducing the bias I did some 
playing and it now appears that to load the final fully I need to set the 
grid current in the range of 10 - 12 MA to get 320 MA of plate current. So 
my next question is what the heck is going on?

Thanks and 73's,
Harry
W0LS
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