[NJARC] Radio Debugging PS

[Scott Roberts]

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


      ____________________________________________________________________________________
Never miss a thing.  Make Yahoo your home page. 
http://www.yahoo.com/r/hs