[AMRadio] 813 Triode Connected Bias question.


Bernie Doran qedconsultants at embarqmail.com
Sat Mar 21 13:09:29 EDT 2015


a simple internet search will show numerous triode connected 813s. Bernie 
W8RPW
----- Original Message ----- 
From: "Larry Szendrei" <ne1s at securespeed.us>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Saturday, March 21, 2015 10:03 AM
Subject: Re: [AMRadio] 813 Triode Connected Bias question.


> On 3/21/15 5:54 AM, Rob Atkinson wrote:
>> http://www.pentalabs.com/pdfs/pl813.pdf
>>
>>
>> Rob
>> K5UJ
>>
>> On Fri, Mar 20, 2015 at 9:37 PM, Paul Baldock <paul at paulbaldock.com> 
>> wrote:
>>> I'm think it will be just a few volts for the 813 triode configuration.
>>>
>>> I could figure the voltage by putting a 1K pot in the center tap and
>>> adjusting it for 20mA, (this would allow 20V max). Then when I know the
>>> voltage, replace the pot with a zener or string of diodes with parallel
>>> electrolytic.
>>>
>>> - Paul
>>
> Appreciate the link to that data sheet, Rob. Saved for future reference.
>
> However, there is no data for use in the triode class B connection, and 
> that is what Paul is looking for.
>
> In the absence of that data I think his suggested approach of putting a 
> pot in the cathode lead (center tap of fil. xfmr) to find the correct 
> operating point and then replace with a Zener (or forward-biased diode 
> string) of the correct value is a good one, and the one I would probably 
> use.
>
> 73,
> -Larry/NE1S
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