[Amps] L4B biasing

[Carl]

If you are planning to use it as an AM linear at times running about 7-8V 
bias will be more efficient and not hurt SSB IMD.
Ive been using my LK-500ZC that way for years and confirmed on a spectrum 
analyzer.

The same procedure works on other amps and tubes.

Carl
KM1H


----- Original Message ----- 
From: "Jim W7RY" <w7ry at centurytel.net>
To: <amps at contesting.com>
Sent: Thursday, December 25, 2014 1:14 AM
Subject: Re: [Amps] L4B biasing


> 11 diodes (7 volts) is way too much bias voltage.
>
> Better to have about 3 diodes (1N5408). That is what I have found while 
> designing my QSK circuit board for the Drake. The L4 and L4B was designed 
> with Amperex 8802 tubes. They did not require
> bias because the idled at a much lower current than Eimac 3-500 tubes. And 
> the old L4 was designed around the 3-400 (8163) which did not require bias 
> either.
>
> Sure, if you have 3800 volts of plate voltage then 7 volts of bias is 
> fine. The SB220 used a 5.1 volt zenner and the SB220 plate voltage was 
> around 3200 volts.
>
> 73
> Jim W7RY
>
>
> -----Original Message----- 
> From: Paul Baldock
> Sent: Wednesday, December 24, 2014 1:23 PM
> To: mikflathead at aol.com ; amps at contesting.com
> Subject: Re: [Amps] L4B biasing
>
> Yes you should add bias. I added 11 diodes in the center tap of the
> filament trany. So that would be about 7 volts.
>
> - Paul
>
> .At 12:52 PM 12/24/2014, you wrote:
>>I just finished me Drake power supply. I used a Drake transformer and a 
>>doubler board with 8 caps. I have 2600 volts showing on the high voltage 
>>meter. I have eliminated all the bias circuit in the power supply that 
>>Drake used. At idle I show  200 mills of plate current. My question is 
>>should I add a bias circuit? I purchased a W4ZT board but wonder if I need 
>>it. Thanks and Happy Holidays to all.
>>_______________________________________________
>>Amps mailing list
>>Amps at contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>
>
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