[Hallicrafters] Re: Hallicrafters SX-42 alignment from Al Parker.

[Al Parker]

Hi Skip,
    I'm still stumped abt the lack of noticeable difference when changing
C-47.  But it does appear that there's too much capacitance in the ckt, and
C-47 is not having a big effect.  If the coil slug was cracked, or a piece
borken off, the L would decrease & resonant freq. would increase, similar to
decreasing capacitance.
    But, looking at the skem.,  the coil/cap ckt of T-23 has C-48, a mica of
470mmf,  effectively in series with C-47.  This would give a total cap. of
235, and reduces the affect of varying C-47.  It doesn't happen often, but
micas do go bad, as I mentioned b4.  They develop leakage from moisture, and
the capacitance rises.  In my SX-42 2nd IF can, the 2 micas had increased as
much as 50% in value.  C-48 may be your problem.  I don't see anything else
there that would materially increase capacitance, unless there's something
shorted, mis-wired, etc.
    The best way to test a mica is to remove it from the ckt & read it's
value with a bridge, etc., and to put up to it's rated voltage across it &
measure resistance.  Capacitance should be within abt 10%, and resistance at
voltage above 20megs.
    I hope this solves your problem, pse let us know.
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info

----- Original Message -----
From: "Waldo Magnuson" <magnuson at mac.com>
Subject: [Hallicrafters] Re: Hallicrafters SX-42 alignment from Al Parker.


> Hi Al,
>     The dial is set correctly on the shaft.  Changing C-47 doesn't make
> a lot of difference (I've even gone to half of it's 470 pf value).  I
> can peak at 600 kc by adjusting S-36 but when I go to 1500 kc dial
> setting even with C-47 at min. setting peaks with an input freq. of
> 1305 kc.  To even get it close to 1500 kc I have to back the S-36 slug
> almost all the way out.  Something is way off.  If there are any SX-42
> experts on alignment I would sure like any of you to look at the
> schematic and suggest things I could try.  I have heard of slugs
> breaking - is this a possibility?  Help appreciated.
> Skip Magnuson
>

> > Message: 3
> > From: "Al Parker" <anchor at ec.rr.com>
> > Hi Skip,
> >     Are you sure the dial is set correctly on the shaft?  Check it
> > with the
> > tuning cap fully meshed and unmeshed.  The other thing, if you've
> > changed
> > C-47 almost 20% & seen little or no change, you may have changed the
> > wrong
> > one.  I know it's possible on the higher bands to get the osc. freq.
> > on the
> > wrong side of the signal freq. in the SX-42, but suspect it can't be
> > done on
> > the lowest band.  (I've done it on the 5-15mc band).
> >     After messin' with mine for over a yr, I've finally finished it.
> > Last
> > item was that the 2 micas in one of the 455kc IF xfmrs were bad.  Big
> > improvement with good ones.  (sounds like you haven't got that problem)
> >     Hope this is some help.
> > 73,
> > Al, W8UT
> > New Bern, NC
> > BoatAnchors appreciated here
> > http://www.thecompendium.net/radio/
> > http://www.hammarlund.info
> >
> > ----- Original Message -----
> > From: "Waldo Magnuson" <magnuson at mac.com>
> > To: <hallicrafters at mailman.qth.net>
> > Cc: "Waldo Magnuson" <magnuson at mac.com>
> > Sent: Thursday, July 24, 2003 5:18 PM
> > Subject: [Hallicrafters] SX-42 alignment - help needed.
> >
> >
> >> Help - Help - Help
> >> I'm trying to align my SX-42 (after recapping it) at 1500 kc / 600 kc
> >> on band 1 but am unable to get any peaking near 1500 kc when adjusting
> >> C-47, 6, 21 & 35.  With the dial at 1500 kc, the output (400 Hz) comes
> >> in at around 1330 kc by changing the input.
> >> At 600 kc I can get a peak by adjusting S-36.  I've tried reducing
> >> C-47
> >> from 470 pf to 390 pf but with little effect.  The IF peaks up ok.
> >> Any suggestions on what to try?  All and any help would be
> >> appreciated.
> >>   Thanks.
> >> Skip Magnuson   KD7VRM