[NJARC] Buzzzzzzzz

[Al Klase]

I concur with John on low sensitivity.  However, if signal is stronger 
at the 6A7 (converter) grid than the antenna terminal, then the problem 
is upstream from that point, i.e. RF amp or antenna circuit, rather than 
downstream in the IF or audio.

Must say I lost track of which radio was involved.

Try using a transistor portable set to track down the source of your 
Buzzzzz.  (Was that enough Z's?)

Al

john ruccolo wrote:
> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Hi Scott,
>
> I too am a proud member of "The 700 Club." That is,
> buzz below 700 KC (in my case I think it goes higher).
> Harry is right on -- one culprit is night sensors on
> our outside spotlights, I proved that recently. 
>
> Listen carefully -- don't confuse low *volume* with
> low *sensitivity*. If it sounds nice and LOUD when you
> put your finger on the cap of the 75, then volume is
> not the issue. But it sounds from your description
> like it is a sensitivity issue.
>
> Low sensitity can be caused by lots of things -- you
> may be on the right track with the 6A7. My prime
> suspect, however, would be the IF amplifier tube, or
> its associated components. What kind of tube is that?
> Swap it out if you have a spare.
>
> I'm not familiar with the term "NFG." Is that a
> military term? ;-)
>
>
> JR
>
> --- Scott Roberts <ng19delta at yahoo.com> wrote:
>
>   
>> Visit our web site - See http://www.njarc.org
>> _______________________________________________
>> Harry- Thanks for the reply. I tried adding a filter
>> to the line in, but no joy.
>>
>> Everyone-
>>
>> Today I pulled the tuning rack, and gave it a good
>> cleaning, also blew the dust out of the coil cans,
>> and
>> trimmers... Now I have to tighten up the
>> realignment:
>> I did a rough one based on a strong local station,
>> but
>> need to fine tune, so to speak...
>>
>> I find if I touch my finger to the grid cap on the
>> 6A7
>> "Osc. Mod." tube, the signal picks up immensely: If
>> I
>> touch the end of the connected "hank antenna" line,
>> it
>> picks up, but not as much... I had the tube marked
>> "weak" in my notes, and I think this confirms the
>> idea...
>>
>> Also, marked "NFG" in my notes is the 75 "DET.-AVC
>> -A.F." tube... If I put my finger on the grid cap,
>> the
>> buzz picks up quite a bit. 
>>
>> The 25Z5 tube is loose in its base(not socket)
>>
>> The radio is working, but weak, unless I am holding
>> the antenna line. I am wondering if the tho tubes
>> (6A7
>> & 75) could be the problem...
>>
>>
>>
>>     
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>   
>>>> _______________________________________________
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>>>>
>>>>   
>>>>         
>>> :Hi Scott,
>>>
>>> Well, all of my radios buzz zzzzz below about 740
>>>       
>> or
>>     
>>> 730 or so. I don't 
>>> know exactly what devices
>>> in the house do it, but it's a common problem.
>>>
>>> Maybe light dimmers, or florescent lights or -
>>> something. One of these 
>>> days I'll track it down.
>>>
>>> Meanwhile, you're not alone.
>>>
>>>                        Harry K
>>>
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>>> NJARC at mailman.qth.net
>>> http://mailman.qth.net/mailman/listinfo/njarc
>>>
>>>       
>>
>>      
>>
>>     
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>
>
>
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-- 
Al Klase - N3FRQ
Flemington, NJ
http://www.skywaves.ar88.net/