[NJARC] Radio Debugging PS

[Al Klase]

Close enough for government work! - Al

Scott Roberts wrote:
> Visit our web site - See http://www.njarc.org
> _______________________________________________
> The schematic shows it going through cap C-40(10mfd electrolytic)
> parallel with resistor R-25(950 ohm) then to ground as you said.
>
> Is there any problem with it showing +5.86vdc?
>
> Scott
>
>
> --- Al Klase <al at ar88.net> wrote:
>
>   
>> Visit our web site - See http://www.njarc.org
>> _______________________________________________
>> The 6R7. pin 8 thing has got to be an error in the
>> documentation.  This 
>> is the cathode of the triode, and goes to GROUND through a
>> resistor.  
>> Normal voltage at that point can't be anything less than zero.
>>
>> Al
>>
>> Scott Roberts wrote:
>>     
>>> Visit our web site - See http://www.njarc.org
>>> _______________________________________________
>>> Hi John- I'll reply to point:
>>>
>>>   
>>>       
>>>> I *strongly* recommend replacement of the main power
>>>> supply filter caps... ...22/250
>>>> should do nicely (which you have, I think)
>>>>     
>>>>         
>>> Yes- I have them: still seem small to me...lol... I will put
>>>       
>> them
>>     
>>> in straight away.
>>>
>>>   
>>>       
>>>> Regarding your voltage measurements always keep in
>>>> mind two things:
>>>>     
>>>>         
>>>   
>>>       
>>>> The original Hallicrafters measurements were probably
>>>> taken with a 1,000 ohms per volt VOM, which loads the
>>>> circuit a little. 
>>>>     
>>>>         
>>> Yes- manual called for 1000ohm per volt VTVM.
>>>
>>>   
>>>       
>>>> Your DVM does not load the ckt at
>>>> all. (Except for grid voltages, where Halli. may have
>>>> used -- at least *should* have used -- a VTVM.)
>>>>     
>>>>         
>>> Should I recheck with a VTVM?
>>>
>>>   
>>>       
>>>> Line voltage then was probably 110V.
>>>>     
>>>>         
>>> Manual calls for 115VAC 
>>>
>>>   
>>>       
>>>> Today's higher
>>>> line voltages jack all the measurements up, at least a
>>>> little bit. I'm *very* surpsied that your line voltage
>>>> is only 113V. 
>>>>     
>>>>         
>>> 113 was through Variac. 119 is line voltage- numbers go up a
>>> little when direct feed.(i.e: 6K7(IF Amp 1) goes up to 297
>>>       
>> from
>>     
>>> 269.5 on 119VAC)
>>>
>>>   
>>>       
>>>> OK, so much for that -- you took all of these
>>>> measurements, but what is the radio DOING? Is it
>>>> receiving *anything*? What are the symptoms? It does
>>>> appear that something is wrong with the BFO, but
>>>> that's no big deal.
>>>>     
>>>>         
>>> Radio was, as dictated in manual- antenna & ground
>>>       
>> disconnected,
>>     
>>> RF & AF gain at Max(when I switched RF into max, got a
>>>       
>> snapping
>>     
>>> noise, like motorboating, but only briefly), no speaker
>>>       
>> hooked
>>     
>>> up. BFO numbers were all wacky- cannot access bottom of
>>>       
>> socket,
>>     
>>> used testing adapter between tube and socket. Tested in both
>>>       
>> "On"
>>     
>>> and "Off" positions.
>>>  
>>>   
>>>       
>>>> Some of those measurements should be *negative*
>>>> (control grids). Just a few volts in most cases. Check
>>>> those again.
>>>>     
>>>>         
>>> Yes- 6R7G #8 pin should read -7, reads +5.86
>>>  
>>>   
>>>       
>>>> Lastly, the 10.450V in place of 10/25V IS overkill.
>>>> Get that outta there. We have a few 10/50V caps left.
>>>> They're tiny, and I think they're only 10 cents each!
>>>>     
>>>>         
>>> Yep- I have it: just seemed SO DA** SMALL! (I still have
>>>       
>> trouble
>>     
>>> accepting the small sizes of newer electrolytics...lol)
>>>   
>>>       
>>>> Regards,
>>>>
>>>> JR
>>>>     
>>>>         
>>> Right now, I am tracing the electrical paths, to see if there
>>>       
>> may
>>     
>>> be some resistor issues. I will replace the overkill and the
>>>       
>> two
>>     
>>> original 16mf electrolytic caps, and retest. Should I hook up
>>>       
>> the
>>     
>>> speaker? And should I use a VTVM of my DMM instead?
>>>
>>> Thanks!
>>> Scott
>>>
>>>
>>>      
>>>       
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>>>   
>>>       
>> -- 
>> Al Klase - N3FRQ 
>> Flemington, NJ 
>> http://www.skywaves.ar88.net/
>>
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>>     
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>   

-- 
Al Klase - N3FRQ 
Flemington, NJ 
http://www.skywaves.ar88.net/