"Paul P" REMOVE paul @ REMOVE ppinyot . REMOVEcom wrote in
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"Richard Knoppow" wrote in
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On Apr 14, 6:38 pm, Bill M wrote:
Richard Knoppow wrote:
Looking at the schematic it appears that bands 1 and 2
have fixed padders in them. For Band-2 its C-11, a 2200
mmf
cap and probably one of the postage stamps. If this has
changed value it will throw off the band. I think this
is
more likely than the coil having shifted. This is a
common
value so a replacement should not be hard to find. I
suggest
changing it before doing anything else.

Trying to follow your posts across the different forums.

The 38 is a plain jane AA5 with shortwave bands, Don't
try to read too
much into it. Image rejection is so poor on the top band
that it really
makes little difference as to how you tune it. You're
welcome to try,
though.

I'm glad you wrote because I mistook the band Paul
was trying to
align. Its band -3 which does not have a padder. So, if
nothing else
seems wrong the coil may need tweeking.
I am pretty sure all the bands on the S-38 series
tune with the
LO above the signal frequency. One can always try it
below. If that's
wrong it won't track properly.
I don't think it has any image rejection at the upper
part of
the top band:-)

Richard Knoppow
WB6KBL


Gentlemen,
A point of clarification:

Band 2 is the problematic band. It covers 1.650 to 5 MHz.
The 5MHz is the oscillator set point. The padder is to be
set at 1.8MHz and does not even come close with the
difference at the 5MHz Osc Trimmer error. This band is
aligned after the 455 IF, BFO and two higher bands are
aligned. After this band is the standard broadcast band.

The padder C11 on band 2 is a variable cap with a postage
stamp (domino) in parallel. I disconnected this parallel
cap in hopes of raising the overall oscillator frequency
to align to 5MHz with no success. It barely made a
difference (no big surprise here).

The other bands align properly starting with Band 4,
13.5 - 32 MHz,
band 3, 5 - 14.5 MHz and last
band 1 broadcast.

I will also check C9 (2700 or 3000pf) in series with the
tuning gang on a hunch. It may have some low end affects.
I did not attempt to calculate the low end cut off point
(collage was too long ago). The band spread has been set
to Zero in accordance to the alignment procedure page
15-62.

I did use carbon composition resistors in front of the
first IF for Rs 1, 2, 3, 20 & 21.

I will try all the suggestions today. I spoke with the
owner yesterday. He wound up in the hospital with a
chainsaw gouge in his leg. He and another were at our ham
club cutting trees and had an accident. I want to get
this chassis working great for him. Your help is helpful.

As always, thanks for all the input!

Paul P.
OK then I wasn't wrong about which band was the
problem:-) However, in the Rider's manual from Nostalgia
Radio C-11 is shown as a fixed 2200 uuf cap.
I also found a PDF of the original Hallicrafters
handbook. This also shows a 2200 uuf fixed cap in the padder
position. The component numbers are different from the
Rider's sheets, in the Hallicrafter's book this cap is
called C-16 and is listed as a 600V mica. For band-2 the
only adjustment is the trimmer, C-21 (in the H book). If the
low end is off or if the entire band is off I suspect C-21
or else coil damage. The S-38 does have an adjustable padder
for Band-2 but the S-38A and S-38B do not. So, I suspect
someone added the adjustable cap for some reason, perhaps
because of the problem you are having. Anyway. I would
remove it, put a 2200 uuf mica cap there and see what you
get. If the thing is still off check the coils and value of
the trimmer, maybe someone substituted it.


--
Richard Knoppow
Los Angeles
WB6KBL