[ARC5] C-30 missing...

[Geoff]

The general designers rule of thumb is that the reactance of the cap, at the 
lowest frequency to be amplified, does not exceed one tenth the value of the 
cathode resistor.


----- Original Message ----- 
Subject: Re: [ARC5] C-30 missing...


> Faulty memory. With 1500 Ohm, the -3 dB point is more like 7 Hz - the 
> original OPT won't respond.
> Brian, VK2GCE.
>
>
>
>> brianclarke01 at optusnet.com.au wrote:
>>
>> Hello Ken,
>>
>> The -3 dB point for 400 Ohm and 15 uF is 26.5 Hz. The original audio
>> output transformer probably has a -3 dB point at 250 to 300 Hz. So, you
>> probably can't tell re frequency response. Now if the NDB's signal  is
>> very strong, you won't notice the effect of negative feedback either.
>>
>> I'll get back to you on the fasteners soon - can't while I'm at work.
>>
>> 73 de Brian, VK2GCE.
>>
>>
>> > Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
>> >
>> I am curious: in the previously-hacked BC-453B I am presently working
>> on,
>> C-30, the 15 mfd 35 VDC cathode-bypass capacitor for the 12A6 audio
>> output tube is missing. Apparently the original hacker removed it but
>> never
>> put it back.
>>
>> Even so, the audio output from this receiver is very loud. Plenty loud
>> enough
>> for a loudspeaker. I am using a 600 ohm to 8 ohm transformer feeding a
>> Radio Shack small 4" square CB speaker. If I turn the RF gain all the
>> way up,
>> it will literally drive me out of the shack.
>>
>> So, is that capacitor really needed?
>>
>> I thought that if one removed that capacitor, some negative feedback
>> would
>> result, and the audio distortion would be reduced, but that the volume
>> would
>> be reduced also.
>>
>> FYI, the B+ is 240 VDC under load.
>>
>> I am copying an NDB, call is MW, here even in the daytime.
>>
>> Ken W7EKB
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