|
Hello again guys.
Performing the RF alignment of the S-85 I am refurbishing, I got the following problem in bands 1 and 2.
?
The setup conditions were as per service manual:?
Sig-gen (HP 8640B) connected to the rig via my DIY RTMA Dummy Antenna. Signal level -80dBm , AM modulation at 30%.
Dials, switches and regulations as per service manual.
The OSC setup went trough seamlessly allowing a quasi perfect dials alignment.
Unfortunately ?C4 and C15 (ANT and MIXER band1) and C3 and C14 (ANT and MIXER band2) didn't peak and had to be set at minimum capacitance (all open) ?just to get the higher output signal possible.
?
Does anybody have any idea about the cause of such a problem and/or suggestion on how to fix it?
?
Thank you very much.
Emanuele (IU1KNR).
https://egirland.blogspot.com
|
My first thought is the bandswitch.? Work it back and forth and use some deoxit or other contact cleaner.? Of course inspect it and use your DMM to verify continuity too.? You mention problems with Bands 1/2 but the manual has you align the high bands first.? Do the high bands work ok?? If none of the bands work right, try tracing the signal through each stage.? Inject your signal at the ANT and probe with a scope S1A-front, C3/C4, S1A-rear, etc.
|
Emanuele, we are happy to see your success so far! We wonder firstly if band 1 and 2 work = bring in stations at all? It seems strange that 2 bands have the same symptoms, and they are in the first RF and the second RF tuning; in total 4 wonky circuits all acting the same way. ?? Could you have unintentionally moved the bandspread to counterclockwise ??before doing 2, and 1 ? Also, it is sometimes possible to accidentally tune onto image frequency and get trapped on the image frequency rather than the desired one. From the ranges I think the images should all be above the desired frequency by 910 Kc/s. If it is accidentally ?near the image now, I am wondering if you begin again on these bands with the cap fully in maybe it will latch onto the desired frequency first. There must be a better way to state all that stuff, but it is a thought. ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Emanuele Girlando via groups.io
Sent: Monday, February 3, 2025 3:21 PM
To: [email protected]
Subject: [HallicraftersRadios] S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!? Performing the RF alignment of the S-85 I am refurbishing, I got the following problem in bands 1 and 2. The setup conditions were as per service manual:?
Sig-gen (HP 8640B) connected to the rig via my DIY RTMA Dummy Antenna. Signal level -80dBm , AM modulation at 30%.
Dials, switches and regulations as per service manual.
The OSC setup went trough seamlessly allowing a quasi perfect dials alignment.
Unfortunately ?C4 and C15 (ANT and MIXER band1) and C3 and C14 (ANT and MIXER band2) didn't peak and had to be set at minimum capacitance (all open) ?just to get the higher output signal possible.
Does anybody have any idea about the cause of such a problem and/or suggestion on how to fix it? https://egirland.blogspot.com -- don??? va3drl
|
Thank you for the advises guys.
The problem is not solved though.
?
Bands 3 & 4 RF alignment went very well, even if the trimcaps were very touchy.
I went through the bands 1&2 alignment process again.
On bands 1 & 2 I am injecting a -90dBm signal from an HP 8640B sig-gen. I don't expect to have any close in image signal under these conditions. I looked for them tuning around the two alignment frequencies and found none, nope.
The band spread dial was set to fully clockwise and it was not moved during the process.
The band switch works ok, it has been cleaned carefully: it doesn't even produce scratches sounds while operated.
I also replaced V1 with a same type I have in hands (both measured "good" on my tube tester).
The radio works like a charm: I spent the entire yesterday night listening to broadcast and ham stations on all bands.
?
Now the questions are:
- why is this happening in the first place?
- how to try to further reduce the trimcap capacitance without destroying them and avoiding to dismantle the relevant RF sections?
- Can it be C7A and C7B went out of value, enough to influence band 1&2 but not enough to influence bands 3&4?
How to test this?
- can it be my RTMA dummy antenna?
?
Thank you very much.
Emanuele (IU1KNR).
?
|
Well those L/C networks are tuned circuits.? If you can't achieve proper resonance then either the signal is not getting to/from them or there is some fault with them.? Check the coil wiring.? Compare to the other band coils.? You should see similar construction.? Make sure the coils aren't open.? Make sure the caps aren't shorted (the mica or polymer dielectric isn't damaged).? You may have to electrically isolate (lift one side) of these components in order to measure but be careful.? It's interesting that you are getting at least reasonable performance under these conditions.
?
Maybe before unsoldering anything you could measure the RF signal at the input or output of V1.? As you adjust the appropriate cap you should see the signal there change quite a bit.?
Now this may sound silly, but make sure you are adjusting the correct cap(s) for the band!? Maybe there's a mistake in the manual?? Verify the caps you are adjusting are the ones in-circuit by looking at the band switch wafers.
?
Nick
|
Emanuele People would love to have a single conversion receiver that has no images up at 28Mcs. ?signals that are too weak wont be heard, but stronger ones and the sig gen should come in 910Kc apart, one weaker than the other. ?I guess you turned the trimmers for 1,2 all in before doing the alignment again and they had to be shifted all out again? And still not good enough. Maybe you could pull the RF tube and inject after the tube so there is only one set of coils to do… as a test. Do you have ?scope so you can look at the RF close to the various coils? It is a mystery. ???? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Emanuele Girlando via groups.io
Sent: Tuesday, February 4, 2025 5:29 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!? Thank you for the advises guys. The problem is not solved though. Bands 3 & 4 RF alignment went very well, even if the trimcaps were very touchy. I went through the bands 1&2 alignment process again. On bands 1 & 2 I am injecting a -90dBm signal from an HP 8640B sig-gen. I don't expect to have any close in image signal under these conditions. I looked for them tuning around the two alignment frequencies and found none, nope.
The band spread dial was set to fully clockwise and it was not moved during the process.
The band switch works ok, it has been cleaned carefully: it doesn't even produce scratches sounds while operated.
I also replaced V1 with a same type I have in hands (both measured "good" on my tube tester).
The radio works like a charm: I spent the entire yesterday night listening to broadcast and ham stations on all bands.
·?????? why is this happening in the first place? ·?????? how to try to further reduce the trimcap capacitance without destroying them and avoiding to dismantle the relevant RF sections? ·?????? Can it be C7A and C7B went out of value, enough to influence band 1&2 but not enough to influence bands 3&4?
How to test this? ·?????? can it be my RTMA dummy antenna? ? Thank you very much.
Emanuele (IU1KNR).
-- don??? va3drl
|
I am catching up on this one. The S-85 is a late version of a
receiver that goes back in Hallicrafters history to the S-20R, maybe
even before. It is about a second step up from the simplest receivers of
the 5 tube AC/DC variety. I have both an S-20R and S-40A, both work very
well. Now, these are simple single conversion receivers with the benefit
of an RF stage. You say you are having trouble on bands 1 and 2, those
are the lowest frequency bands, please confirm this. Mostly I would
expect alignment trouble on the two higher bands, 3 and 4. Perhaps we
have been chasing the wrong bands.
The S-85 has a calibrated band spread on all bands. It has one
additional band spread condenser compared to the earlier models. The
band spread capacitor is separate from the main tuning cap but is common
to all four bands.
If you were having trouble on the higher bands I would suspect you
are on the wrong side of the local oscillator, i.e. trying to tune on
the image rather than the fundamental response. Some multi band
receivers tune with the local oscillator higher than the signal
frequency for the low bands and with it below the signal for the highest
or two highest bands. If you are on the wrong side the RF will not track
the oscillator so you may get strong signals at one end but not the
other. I did not see in the S-85 handbook which side you are supposed to
use but in earlier receivers the LO is BELOW the signal on the highest
band but ABOVE it on the other bands.
If you are getting NO signal on the two lowest bands I would look at
the band switch. This is a pretty unusual problem.
The S-85 is pretty much an old, reliable design and should not have
many exotic problems.
Sorry if this is all asked and answered but I have not gone over the
entire thread.
Also, I don't know what you mean by "close to" images. There will be
ONE image, it will be separated by twice the IF frequency, for this
receiver. 910Khz.
More info please.
toggle quoted message
Show quoted text
On 2/4/2025 2:28 AM, Emanuele Girlando via groups.io wrote: Thank you for the advises guys.
The problem is not solved though.
*Bands 3 & 4 RF alignment* went very well, even if the trimcaps were
very touchy.
I went through the bands 1&2 alignment process again.
On bands 1 & 2 I am injecting a -90dBm signal from an HP 8640B sig-gen.
I don't expect to have any *close in image signal* under these
conditions. I looked for them tuning around the two alignment
frequencies and found none, nope.
The *band spread* dial was set to fully clockwise and it was not moved
during the process.
The *band switch* works ok, it has been cleaned carefully: it doesn't
even produce scratches sounds while operated.
I also replaced *V1* with a same type I have in hands (both measured
"good" on my tube tester).
*The radio works like a charm*: I spent the entire yesterday night
listening to broadcast and ham stations *on all bands*.
Now the questions are:
* *why* is this happening in the first place?
* how to try to further *reduce the trimcap capacitance* without
destroying them and avoiding to dismantle the relevant RF sections?
* Can it be *C7A and C7B went out of value*, enough to influence band
1&2 but not enough to influence bands 3&4?
How to test this?
* can it be my RTMA *dummy antenna*?
Thank you very much.
Emanuele (IU1KNR).
<>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Things get darker and darker.
- Coils are not open.
- TRIMCAPs are not shorted.
- I confirm problem in band 1&2, bands 3&4 worked like a charm.
Started from scratch.
Test gears setup:
The Spectrum Analyzer is an Advantest 3361B (0.1-3600Mhz) driven by a 10MHz EXT REF coming from a rubidium reference oscillator. I performed the calibration procedures before using it.
The RF probe is an active probe able to reach 500Mhz. Its input is very high-Z. Loosely coupled (gimmick cap) to T3-pin2 (3rd IF output, just before the detector..).
Tracking generator output connected to V8-pin2 trough a 2000pF cap as per service manual.
NOTE: in all the following test the vertical measures a purely qualitative. Horizontal measures are quantitative measurements.
I performed a visual IF alignment using the SA tracking generator.
?
?
The IF cans peaked @452KHz, the BW is 5.9KHz.
The IF strip seems ok to me. Do you agree?
?
Local oscillator actual frequency test:
I relocated the probe input to loosely couple ?(gimmick cap) the local oscillator.
Sig-gen (HP 8640B) @1400KHz, AM modulated @30% connected to ANT by a RTMA dummy antenna. Used as a reference for dial setting.
Here is the plot of the local oscillator signal in the Band 1 tuned @1.4MHz. It seems ok to me (1400+452= 1852 KHZ):
?
Sig-gen (HP 8640B) @4000KHz, AM modulated @30% connected to ANT by a RTMA dummy antenna. Used as a reference for dial setting.
Here is the plot of the local oscillator signal in the Band 2 tuned @4MHz. It seems ok to me (4000+452=4452 KHZ):
?
I think these tests can get the "image" frequency topic out of discussion.
Do you agree?
I then tried to isolate the problem stressing the ANT resonant circuit alone, with the following setup:
The S-85 was turned OFF.
Band spread dial fully clockwise in all tests.
NOTE: in these last tests the right marker is where the peak should be.
?
On band 1, with the Main Tuning dial set to 1.4Mhz (as per service manual), i've got the following results:
??????????? TRIMCAP C4 fully engaged (higher C):?????????????????????????????????????????????????????????????????????????????????? TRIMCAP C4 fully released (lower C):
?
The peak is lower then the test frequency between 370 and 220 KHz - not normal!
The steep left slope and the asymmetry in general are also suspect. In fact, listening on band 1, all signals (and the noise as well) tend to disappear below .5MHz.
?
On band 2, with the Main Tuning dial set to 4Mhz (as per service manual), I've got the following results:
??????????????????????? TRIMCAP C3 fully engaged (higher C):???????????????????????????????????????????????????????????????????????????????????????????????????????????? TRIMCAP C3 fully released (lower C):
The peak is lower then the test frequency between 1MHz and .7MHz - not normal!
At least the slope is symmetric.
?
Removing V1 produced no significant change.
?
Conclusions:
- the tanks do resonate.. but at the wrong frequency. In both cases the peaks always stay far below the tuning frequencies.
- Band 1 also suffer strong slope asymmetry. Listening the radio it looses sensitivity below .5MHz. Why is that?
- The reasonable performances I get from the receiver are due to "partial" signal passing through even if the corresponding tank doesn't resonate correctly.
HELP!
Emanuele (IU1KNR).
?
|
We are talking about a Hallicrafters S-85 are we not? The S-85
tunes from 535 Khz to 34Mhz. So, what is this about .5Mhz and 370 and
220 Khz? typo maybe.
Since the higher bands work I assume you aligned the IF. Perhaps
worth just starting there. Feed in 455 Khz. You can feed the antenna
terminals. Adjust using 30% modulation at some reasonable frequency, say
500 Hz. Use the lowest signal strength that gives you noise free audio.
Tune for maximum output keeping the input level as low as possible. This
will prevent a resonant shift due to AVC.
When done go on to the RF alignment. Follow the instructions. The
S-85 starts with the high band and goes down.
I could not find a reference to which image is used on the high
bands but its important to be on the correct one. It is common on these
receivers to align the local oscillator "Below" the signal on the
highest band and "Above" it on the other bands. If you are on the wrong
side the RF will not track and the calibration of the oscillator will be
off. If you find this try the other side.
The position of the peaks on the RF will be affected somewhat by
the dummy load. Its worth using one if you can but reasonable alighment
can be gotten without one.
The IF symmetry depends on the coupling of the IF transformers and
for a fixed bandwidth IF should be close. If its way off you have a bad
transformer but I think more likely have a measurement error. Just peak
the transformers and go on to the RF.
It is amost impossible for you to be getting good signals on the
high bands and nothing on the broadcast band. I measurement error I think.
Start over from the beginning and keep it simple! I think its
possible your test frequencies are way off.
Please report what you find.
Note that on the high bands it may be necessary to rock the tuning
because the RF adjustments may pull the oscillator slightly. Not the
cause of your problem. Also a reason to keep the signal levels as low as
possible.
toggle quoted message
Show quoted text
On 2/5/2025 2:20 PM, Emanuele Girlando via groups.io wrote: Things get darker and darker.
* Coils are not open.
* TRIMCAPs are not shorted.
* I confirm problem in band 1&2, bands 3&4 worked like a charm.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Emanuele here is your suff edited a bunch ? Things get darker and darker. ???No.. just more interesting - - Coils are not open.??????????????? good
- TRIMCAPs are not shorted. good
- I confirm problem in band 1&2, bands 3&4 worked like a charm. ??
I then tried to isolate the problem stressing the ANT resonant circuit alone, with the following setup: ?ok The S-85 was turned OFF.
Band spread dial fully clockwise in all tests. NOTE: in these last tests the right marker is where the peak should be. On band 1, with the Main Tuning dial set to 1.4Mhz (as per service manual), i've got the following results: ??????????? ?????????????????????????????????????????????????????????????????????????????????????????????TRIMCAP C4 fully released (lower C): my markups Do I read this correctly ?? ?if so? the First RF ?almost tunes to 1400? so as you said , not an image problem. And it is just a bit off. However is the 600 kc area is poor in sensitivity? we have to think harder.?? I am on overtime now, so will look tomorrow ? -- don??? va3drl
|
Don,
here is my picture interpretation:
?
Richard:
- "So, what is this about .5Mhz and 370 and 220 Khz? ". Those are the delta values between peak and the desired frequency as reported by the Delta marker (rounded).
- The IF alignment has been remade from scratch by using the "visual" approach (first 3 pictures).
- "The position of the peaks on the RF will be affected somewhat by the dummy load". If you meant the "dummy antenna" I fully agree. I'm gonna try the same test removing the dummy antenna from the equation. I'll report as soon as I get time to work on that.
Correction to my previous post:
"...all signals (and the noise as well) tend to disappear below .5MHz" should read "... below 1MHz" that is in the lower half of the band.
?
Thank you guys!
Emanuele (IU1KNR).
?
|
Hy.
I can confirm that the dummy antenna is not influencing the peaks points.
I tried the tests just getting the TG output physically close to the antenna connector and nothing changed but the vertical values..
?
Emanuele (IU1KNR).
|
Emanuele
I NEED EDUCATION ?on reading these new scopes and such Wrt your previous post; I have no reason to believe there is a problem in the IF. My last post made wrong assumptions on the reading the scope, so my conclusions are wrong; and I agree the RF tuning on the first tank in band 1? is way out it seems. I keep wondering why 4 tanks seem to have the same problem. ?Is it possible that the bandspread dial stringing is reversed? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Emanuele Girlando via groups.io
Sent: Thursday, February 6, 2025 4:25 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!? here is my picture interpretation: ·?????? "So, what is this about .5Mhz and 370 and 220 Khz? ". Those are the delta values between peak and the desired frequency as reported by the Delta marker (rounded). ·?????? The IF alignment has been remade from scratch by using the "visual" approach (first 3 pictures). ·?????? "The position of the peaks on the RF will be affected somewhat by the dummy load". If you meant the "dummy antenna" I fully agree. I'm gonna try the same test removing the dummy antenna from the equation. I'll report as soon as I get time to work on that. Correction to my previous post: "...all signals (and the noise as well) tend to disappear below .5MHz" should read "... below 1MHz" that is in the lower half of the band. -- don??? va3drl
|
Which way is the band spread capacitor facing? Capacitance should
be minimum with dial at zero. This is Halicrafters design, on
non-calibrated band spreads the dial indicates the amount of capitance.
I think calibrated dials are set for the logging scale to be the same
but in any case the band set is generally at the high end of the band.
The dial cord is backwards of its orientation on later receivers
like the S-40. The string crosses over.
BTW, I wondered about this. My S-40A came with the band spread
string reversed and stop peg facing the opposite way to that shown in
the handbooks. I reversed it. In its original position the band spread
went from zero to 100 but in what I thought was the correct position it
stops at about 95. Same for the S-20R. It made me wonder if the original
position was correct and there is a global error in the handbooks for
all this series of receivers. The position as shown in the S-85 handbook
seems to confirm this. A puzzle. At some point I will try reversing the
cable in both receivers. In any case, at ZERO the band spread is at
minimum band spread capacitance, plates turned out from stator, this is
as it should be regardless of the cord.
toggle quoted message
Show quoted text
On 2/6/2025 1:13 PM, don Root wrote: Emanuele
I NEED EDUCATION ?on reading these new scopes and such
Wrt your previous post; I have no reason to believe there is a problem
in the IF.
My last post made wrong assumptions on the reading the scope, so my
conclusions are wrong; and I agree the RF tuning on the first tank in
band 1? is way out it seems.
I keep wondering why 4 tanks seem to have the same problem. ?Is it
possible that the bandspread dial stringing is reversed?
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Emanuele Girlando
via groups.io
*Sent:* Thursday, February 6, 2025 4:25 AM
*To:* [email protected]
*Subject:* Re: [HallicraftersRadios] S-85 refurbish: I've got a problem
during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Don,
here is my picture interpretation:
Richard:
·"/So, what is this about .5Mhz and /*/370/*/and /*/220/*/Khz?/ ". Those
are the delta values between peak and the desired frequency as reported
by the Delta marker (rounded).
·The IF alignment has been remade from scratch by using the "visual"
approach (first 3 pictures).
·"/The position of the peaks on the RF will be affected somewhat by the
dummy load/". If you meant the "dummy antenna" *I fully agree*. I'm
gonna try the same test removing the dummy antenna from the equation.
I'll report as soon as I get time to work on that.
Correction to my previous post:
"/...all signals (and the noise as well) tend to disappear below /
*/.5MHz/*" should read "... below *1MHz*" that is in the lower half of
the band.
Thank you guys!
Emanuele (IU1KNR).
<>
--
don??? va3drl
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Wait a minute guys ... SORRY guys!!!!!
?
Using the SA for RF alignment led me astray, .. and you all with me!
Don, you say need education ... from my side I would say I need a medical treatment for my brain!!
?
We are not looking for the peak at the resonant frequency, as you would do aligning an IF, but we are looking for the MAX at the indicated frequencies. Operating this way the? entire response curve of the band takes on an ideal shape and the peak will be placed approximately in the middle.
?
This picture sketches what I mean...
?
Looking that happenin in real time makes things much more clear.
This also explains why the radio is performing well.
?
Still, band 1 & 2 won't get to a MAX at the indicated frequencies.
Releasing the TRIMCAPs from fully tight to fully released the signal (and the entire curve with it) goes always up and never down until the TRIMCAP reaches its end stop.
I would say: they go to "highest possible value"...
?
Emanuele (IU1KNR).
?
|
Richard, we do cross posted.
Today I also started to think the band spread variable capacitor was stringed reversed..
But I checked it and, in fully clockwise position (the one indicated for alignment), the cap is at minimal capacitance (blades all out).
?
Emanuele (IU1KNR).
|
Richard you deleted my image in the reference so others might wonder about some stuff missing, but no real matter there. My thought to verify the bandspread is simply to turn the BS dial CW ? and knob? ?CW and look at the BS capacitor meshing. It should be open! ??right? ?If somehow it is not it needs fixing first. ? If it is ok, it’s back to square one. We will have to recruit a real expert. ? Richard ?FYI only now: 
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow via groups.io
Sent: Thursday, February 6, 2025 4:33 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!? Which way is the band spread capacitor facing? Capacitance should
be minimum with dial at zero. This is Halicrafters design, on
non-calibrated band spreads the dial indicates the amount of capitance.
I think calibrated dials are set for the logging scale to be the same
but in any case the band set is generally at the high end of the band.
The dial cord is backwards of its orientation on later receivers
like the S-40. The string crosses over.
BTW, I wondered about this. My S-40A came with the band spread
string reversed and stop peg facing the opposite way to that shown in
the handbooks. I reversed it. In its original position the band spread
went from zero to 100 but in what I thought was the correct position it
stops at about 95. Same for the S-20R. It made me wonder if the original
position was correct and there is a global error in the handbooks for
all this series of receivers. The position as shown in the S-85 handbook
seems to confirm this. A puzzle. At some point I will try reversing the
cable in both receivers. In any case, at ZERO the band spread is at
minimum band spread capacitance, plates turned out from stator, this is
as it should be regardless of the cord.
-- don??? va3drl
|
Where its supposed to be I think.
As far as your last post, I was looking for something like this. I
was tempted to suggest getting rid of the high tech instruments and
sticking to a regular signal generator as prescribed in the
instructions. This is really a very simple receiver and should be easy
to align. Remove as many variables as possible, such as a spectrum
analyzer and sweeper. Maybe after doing an alignment with the simplest
tools. A modern signal generator will have reasonable calibration
accuracy for both frequency and output level. A counter or even just a
crystal calibrator will do for adjusting dial calibration. The spectrum
analyzer is helpful for signal tracing, if necessary, and to determine
which side of the local oscillator the signal is on. On the broadcast
band its possible that if you are on the wrong side (will be below the
signal) you will simply run out of range at the low end. That could be
what is wrong. Actually, a simple broadcast receiver should hear the LO
and tell you where it is. Should be the signal frequency plus 455Khz.
Obviously, if its tuning below the signal it will probably stop
oscillating at some point. At the lowest frequency of the broadcast
band, usually 535 Khz, the LO would have to be at 80Khz. Might be the
reason it stops working at about mid band. Again, its likely the top
band is opposite of the others, i.e. the LO will be below the signal.
This is often the case in older multi-band receivers because the
oscillator/mixer may have higher conversion gain there. Depends on the
tube used. Unfortunately, handbooks often don't tell you this. The
assumption being the tuning will be only touch up and not far from the
factory settings. We are dealing with antiques and some of the
assumptions made by the manufacturer are simply not so.
Good luck, I think you are on your way.
toggle quoted message
Show quoted text
On 2/6/2025 2:20 PM, Emanuele Girlando via groups.io wrote: Richard, we do cross posted.
Today I also started to think the band spread variable capacitor was
stringed reversed..
But I checked it and, in fully clockwise position (the one indicated for
alignment), the cap is at minimal capacitance (blades all out).
Emanuele (IU1KNR).
<>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Note that the direction of the dial and knob for bandspread are
reversed. See instructions about replacing the dial string. The index
mark on the dials is at the LOW end, with capacitors fully meshed. I
read this over carefully. The _band set_ position of the band spread is
with the dial at the high frequency end of each band, that is, capacitor
UN meshed. but the instructions for setting the dials is to fully mesh
the caps and use the index mark at the low end of both dials.
Also, a note states that the LO is at ABOVE the signal on all bands
except the highest (band 4) where it is below the signal (as I suspected).
The problem with clockwise and counter-clockwise is whether this is
the knob or dial direction, because they are opposite. However, looking
at the capacitor plates is unmistakable. Fully meshed for dial stringing
and setting the reference of the dials, band spread fully open when
setting the main dial for frequency and for alignment.
toggle quoted message
Show quoted text
On 2/6/2025 2:25 PM, don Root wrote: Richard you deleted my image in the reference so others might wonder
about some stuff missing, but no real matter there.
My thought to verify the bandspread is simply to turn the BS dial CW ?
and knob? ?CW and look at the BS capacitor meshing. It should be open!
??right? ?If somehow it is not it needs fixing first.
If it is ok, it’s back to square one. We will have to recruit a real expert.
Richard ?FYI only now:
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Emmanuel ??Oh I sent? more cross-posting. Now back at square one ? Entropy is increasing quickly. So you are back to the apparent ?too-much capacitance or inductance, and similar problem for 4 tank circuits.. strange… ?Emmanuel ?we don’t know the history so presumably this radio is new to you. did it ever work ok on band one? Is there a sign of somebody mucking about around the coils and bandswitch. Could there be a cross between band one and two tanks maybe due to little clearance?...another longshot Now I am just wondering out loud, the RF for the 2 HF bands seem to use transformers with slugs, and you can see them on the layout, but for band 1,2 there are trimmers shown but no transformer or coil on the layout so perhaps “L3” has a simple winding for band 1 and another for band 2 ????? same situation and question for the mixer tanks? So what would happen if L3 had a common ground connection terminal and a bad connection to ground ? OR something? ??could L3 have been changed ?another longshot Another thought; I wonder if the alignment instructions are as complete as for older radios.? My thought is that both ends of the oscillator should be set first and any interaction eliminated by repeating the C22 and C25 ?adjustments etc, then set the RF trimmers. It is hard to see it making a big difference… Richard, Emanule, whoever?? A last resort might be to? find the resonant point of each tank at the top end and the bottom end of the main tuning for bands 1 and then 2. ???? Richard has just added some confusion so this is going now as-is only thoughts. ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Emanuele Girlando via groups.io
Sent: Thursday, February 6, 2025 5:21 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!? Richard, we do cross posted. Today I also started to think the band spread variable capacitor was stringed reversed.. But I checked it and, in fully clockwise position (the one indicated for alignment), the cap is at minimal capacitance (blades all out). -- don??? va3drl
|
Emanuele Girlando
don Root