[Hallicrafters] SX-42 Alignment saga

[Rodger]

Hi Rich,

Do you have the IF aligned on the crystal peak frequency?  It is probably
not exactly on 455 khz and you will need to determine the crystal peak and
then realign the IF transformers for this frequency.  After this you will
probably be able to get it to operate properly on all of the xtal filter
settings.

For the RF alignment, you will definitely find the mixer adjustments will
pull the oscillator frequency on the higher bands.  I would do a rough
alignment using your signal generator and then use a noise source to provide
a broad signal for the final peaking of the mixer adjustments.  A nearby
light dimmer, portable kitchen mixer, or the noisy appliance of your choice
should work just fine.  If you have one of the modern little digital
shortwave radios with multiple memories, you can use this to make the
oscillator tracking alignment much easier.  On the SX-62 the oscillator will
be offset by the ~455 khz. IF frequency on the 4 lower ranges and by the
10.7 mhz. IF frequency on the 2 upper ranges.  So for example, on band 1 if
you tune the SX-42 to 600 khz. you should hear the oscillator at 1055 khz.
and at a receiver frequency of 1600 khz. you should hear the oscillator at
2055 khz.  This is assuming your xtal filter and IF is exactly 455 khz., if
it is 457 khz. then you would listen at 1057 and 2057 khz. For me this
process is much faster than moving the generator back and forth while
setting the oscillator tracking.  You will need to check the manual (since I
don't have mine handy) to see if the oscillator tracks below the receiver
frequency on some bands.  I am sure that on bands 1-3 it tracks above the
received frequency and if like many hallicrafters it will have low side
tracking on band 4.  I believe that bands 5 and 6 will use high side
tracking (received frequency +10.7 mHz.) but you should check this in the
manual.  These higher bands are where the little Japanese "DC to daylight"
receivers really become handy as alignment aids.

I cannot remember if you have replaced caps in the receiver but many of the
RF section bypass capacitors are accessible through the removable side panel
over the adjustments for bands 5 and 6.  You will need a good set of needle
nose pliers, plenty of light, and a long tipped soldering iron but it can be
done since I have done so on my SX-42,62 and 62A. 

Persevere, you are making good progress!

73, Rodger WQ9E


> -----Original Message-----
> From: hallicrafters-bounces at mailman.qth.net [mailto:hallicrafters-
> bounces at mailman.qth.net] On Behalf Of Rich Soennichsen
> Sent: Monday, February 19, 2007 10:51 AM
> To: hallicrafters at mailman.qth.net
> Subject: [Hallicrafters] SX-42 Alignment saga
> 
> After getting the BFO working I was charged with confidence (again,
> only have it dashed, again.  A vicious cycle that repeats eternally).
> 
> The next part of the alignment concerns the crystal filter.
> Previously I got no response to my tuning efforts.  I suspected a dead
> crystal so last night I took it apart and in the process broke the
> holder, ugh!  Luckily the material was such that it crazy-glued back
> together nicely.  I simply rubbed the quartz on it contacts a bit and
> put it back together.  It seems to work now!  Of course this rig will
> never throw me a bone....  There are three alignments for the crystal
> filter, sharp, medium, and broad, adjusted with variable caps caps.
> Only the broad setting responded (peaked) as expected.  Ah well, do I
> really need a crystal filter?  Perhaps the rock is not singing
> correctly...
> 
> That's the latest.  Next is the RF section which, I suspect, is a
> whole other can-o-worms.
> 
> Rich
> 
> W7SOE
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