[NJARC] Radio Debugging PS

[Scott Roberts]

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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