[NJARC] Radio Debugging PS

[John Ruccolo]

Hi Scott,

I *strongly* recommend replacement of the main power
supply filter caps. Yes, the PS may be working now,
but I wouldn't trust the caps for long. Why risk a
hard-to-find power transformer for 2 or 3 $ worth of
caps?

I'll have to see if I can order 16/450. But 22/250
should do nicely (which you have, I think), and won't
affect B+ voltage too much.

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. 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.)

Line voltage then was probably 110V. 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. Do you have it "throttled back" with a
variac? If not, that's pretty low by today's
standards.
Mine is typically around 122V, most are between 120
and 125V.

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.

IIRC, the radio was working surprisingly well with
most of the original paper caps in place (but for how
long would be anybody's guess).

Some of those measurements should be *negative*
(control grids). Just a few volts in most cases. Check
those again.

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!


Regards,

JR


--- Scott Roberts <ng19delta at yahoo.com> wrote:

> Visit our web site - See http://www.njarc.org
> _______________________________________________
> PS- I replaced all the paper caps, and a coupe
> electrolytics, but
> NOT the two large electrolytic caps C-44 & C-45,
> both 16mfd @
> 400V. I replaced electrolytic cap C-40, 10mfd @ 25v,
> with a 10mfd
> 450. Is this too big? or just overkill?
> 
> Scott
> 
> --- Scott Roberts <ng19delta at yahoo.com> wrote:
> 
> > Visit our web site - See http://www.njarc.org
> > _______________________________________________
> > Hi Everyone!
> > I am finishing up my recap on the Hallicrafters
> SX-16. Today, I
> > checked the voltages on the tubes, using an 
> Extech True RMS
> > DMM,
> > Model 22-816. I am working with about 113VAC house
> current. 10%
> > tolerances, per manual. Settings IAW Hallicrafters
> manual
> 
> 
> 
>      
>
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