[Milsurplus] OK Smart People- Back Bias

[J. Forster]

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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