[NJARC] Radio Debugging PS

[Al Klase]

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/