[Milsurplus] OK Smart People- Back Bias

[Mike Feher]

Well John, even if that were true, where are those micro amps coming from in that circuit? - Mike

Sent from my iPad

On Jul 31, 2012, at 4:48 PM, "J. Forster" <jfor at quikus.com> wrote:

> Depends on the Zener. Some have very sharp knees in the microamp region.
> 
> -John
> 
> ================
> 
> 
> 
> 
>> Dave -
>> 
>> The Zener idea will not work due to the real high resistance values in the
>> existing circuit of the 474. 73 - Mike
>> 
>> Sent from my iPad
>> 
>> On Jul 31, 2012, at 11:51 AM, "David Stinson" <arc5 at ix.netcom.com> wrote:
>> 
>>> I have a BC-474 receiver that, as originally designed,
>>> uses a backbias resistor in the B- lead to provide audio
>>> PA and AVC bias.  R25 and C21 provide the bias.
>>> Here's the diagram:
>>> 
>>> http://home.netcom.com/~arc5/bias/backbias.jpg
>>> 
>>> I'd like to make a temporary "tacked-in" change so I can
>>> use a supply with B- grounded for a short time.
>>> Will 5-volt zeners connected this way work?
>>> 
>>> http://home.netcom.com/~arc5/bias/zenerbias.jpg
>>> 
>>> Thanks!
>>> 
>>> 
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> 
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