S-38 Questions about alignment.
 

I am restoring now aligning a S-38. Yep, all caps and resistors replaced
except the domino caps and tubes tested, bias voltages with in spec. I gave
up the alignment for now. I am having trouble aligning the Band 2 at 5mc.
The oscillator just dose not want to go high enough. Perhaps a good night's
sleep will help.

Questions:

1) What is the oscillator offset (add or subtract the IF freq 455) for the
four bands? Are any bands different from the others? Broadcast is just
fine at frequency plus IF (455).

2) Are the domino caps paper inside or mica? They are NOT Micamold. There
are three of four of them. I was going to replace them next and heat gun
the coils.

http://www.nostalgiaair.org/PagesByM...2/M0008862.pdf

Thanks,
Paul P

S-38 Questions about alignment.
 

On Apr 13, 6:40*pm, "Paul P" REMOVE paul @ REMOVE ppinyot .
REMOVEcom wrote:
I am restoring now aligning a S-38. *Yep, all caps and resistors replaced
except the domino caps and tubes tested, bias voltages with in spec. *I gave
up the alignment for now. *I am having trouble aligning the Band 2 at 5mc.
The oscillator just dose not want to go high enough. *Perhaps a good night's
sleep will help.

Questions:

1) What is the oscillator offset (add or subtract the IF freq 455) for the
four bands? *Are any bands different from the others? *Broadcast is just
fine at frequency plus IF (455).

2) Are the domino caps paper inside or mica? *They are NOT Micamold. *There
are three of four of them. *I was going to replace them next and heat gun
the coils.

http://www.nostalgiaair.org/PagesByM...2/M0008862.pdf

Thanks,
Paul P

The postage stamp caps are mica but probably not silver mica.
If all the other frequencies come in the problem may be that
something has shifted in the band 2 oscillator coil. Most of these
coils have a couple of spaced turns to adjust the value. You will have
to juggle between the coil and the trimmer.
The S-38B LO is 455 khz above the signal frequency on all bands.

S-38 Questions about alignment.
 

"Richard Knoppow" wrote in message
...
On Apr 13, 6:40 pm, "Paul P" REMOVE paul @ REMOVE ppinyot .
REMOVEcom wrote:
I am restoring now aligning a S-38. Yep, all caps and resistors replaced
except the domino caps and tubes tested, bias voltages with in spec. I
gave
up the alignment for now. I am having trouble aligning the Band 2 at 5mc.
The oscillator just dose not want to go high enough. Perhaps a good
night's
sleep will help.

Questions:

1) What is the oscillator offset (add or subtract the IF freq 455) for the
four bands? Are any bands different from the others? Broadcast is just
fine at frequency plus IF (455).

2) Are the domino caps paper inside or mica? They are NOT Micamold. There
are three of four of them. I was going to replace them next and heat gun
the coils.

http://www.nostalgiaair.org/PagesByM...2/M0008862.pdf

Thanks,
Paul P

The postage stamp caps are mica but probably not silver mica.
If all the other frequencies come in the problem may be that
something has shifted in the band 2 oscillator coil. Most of these
coils have a couple of spaced turns to adjust the value. You will have
to juggle between the coil and the trimmer.
The S-38B LO is 455 khz above the signal frequency on all bands.\


Thanks Richard,

Yes the whole band is shifted. I will look at and chase the coils.

One point of clarification. So that would make 5 MHz look like 5.455MHz on
the oscilator?

Paul P.
KB3LZP

S-38 Questions about alignment.
 

"Paul P" REMOVE paul @ REMOVE ppinyot . REMOVEcom wrote in
message ...

"Richard Knoppow" wrote in
message
...
On Apr 13, 6:40 pm, "Paul P" REMOVE paul @ REMOVE ppinyot
.
REMOVEcom wrote:
I am restoring now aligning a S-38. Yep, all caps and
resistors replaced
except the domino caps and tubes tested, bias voltages
with in spec. I gave
up the alignment for now. I am having trouble aligning
the Band 2 at 5mc.
The oscillator just dose not want to go high enough.
Perhaps a good night's
sleep will help.

Questions:

1) What is the oscillator offset (add or subtract the IF
freq 455) for the
four bands? Are any bands different from the others?
Broadcast is just
fine at frequency plus IF (455).

2) Are the domino caps paper inside or mica? They are NOT
Micamold. There
are three of four of them. I was going to replace them
next and heat gun
the coils.

http://www.nostalgiaair.org/PagesByM...2/M0008862.pdf

Thanks,
Paul P

The postage stamp caps are mica but probably not
silver mica.
If all the other frequencies come in the problem may
be that
something has shifted in the band 2 oscillator coil. Most
of these
coils have a couple of spaced turns to adjust the value.
You will have
to juggle between the coil and the trimmer.
The S-38B LO is 455 khz above the signal frequency on
all bands.\


Thanks Richard,

Yes the whole band is shifted. I will look at and chase
the coils.

One point of clarification. So that would make 5 MHz look
like 5.455MHz on the oscilator?

Paul P.
KB3LZP

Exactly.
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.




--
Richard Knoppow
Los Angeles
WB6KBL

S-38 Questions about alignment.
 

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.

S-38 Questions about alignment.
 

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

S-38 Questions about alignment.
 

"Richard Knoppow" wrote in message
...
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.

S-38 Questions about alignment.
 

Paul P wrote:



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.

Are you able to get the 5Mc point set ok?

Sometimes the solution is to fudge on the dial pointer alignment and
see if the other 3 bands can line up. However, if they are spot on now
that might not be the direction to go.

-Bill

S-38 Questions about alignment.
 

"Bill M" wrote in message
...
Paul P wrote:



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.

Are you able to get the 5Mc point set ok?

Sometimes the solution is to fudge on the dial pointer alignment and see
if the other 3 bands can line up. However, if they are spot on now that
might not be the direction to go.

-Bill

I have done this before on other chassis. This chassis has hard stops at
the dial scale extremes. Moving the pointer will throw the pointer off
where it will not cover the band scale edge. This would be unacceptable on
this chassis.

I can not get the 5Mc aligned. It is fairly far off uniformly across the
whole band. All other bands are dead on the marks.

I am Climbing The Stairway to Heaven (the shop/shack) at this time. I will
report back later.

Thanks Bill,
Paul P.

S-38 Questions about alignment.
 

Paul P wrote:



I can not get the 5Mc aligned. It is fairly far off uniformly across
the whole band. All other bands are dead on the marks.

Ah, ok. Now I'm on board.
No point in fussing with the padder yet, then. Things may fall into
place once you get the top end of the band right.

Just for grins, will the oscillator tune to the lower side (4545)? I
don't *think* it should be that way but ya never know.

-Bill