Re: Hallicrafters Radios for Sale
Hi Don,
?
? ? Not sure if there is more than one model.? ? Come on down to the flea and take a look.
?
The one we have is working and in nice shape.??
?
Regards,
?
? ? ?Gene
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Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
C-62 in the S-40B is a small cap from the plate of the RF amp to
the grid of the converter. In the S-85 there are two such caps, one on
each of the low band tuned circuits. All listed as Bakelite caps. I have
seen illustrations of Bakelite caps somewhere, essentially a very low
value cap made by embedding two wires in a pit of Bakelite. Probably
more accurate and stable than a gimmick. I am no longer certain I can
analyze this circuit but it appears that these small value caps are to
equalize the gain of the RF stage.
I wonder if there was ever a Sam's or Rider's handbook for the S-85
or the S-40B for that matter. Both seem to have redrawn factory
schematics and are often somewhat clearer. I looked but could not find any.
I looked at the photo of the bottom of the S-40B in the handbook
but its not really that clear. My idea was to see of the L-3 coil, which
is for both low bands, was situated such that it could be coupled by
mutual inductance to the other coils.
I also looked at the Radiotron Designer's Handbook to see if there
was anything in it about RF amplifiers. There is but it wasn't helpful.
I have some other material on broadcast receiver design and will keep
looking.
Its too bad that someone with a _working_ S-85 can't look at it and
seen what it actually there. Very frustrating.
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On 2/14/2025 3:07 PM, Emanuele Girlando via groups.io wrote: D
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
I wonder whether too much coupling (or not enough) might affect the
ability to align the stage. I think that you are on the right track.
100 messages? Wow! I can't recall now whether you made the change we
were originally thinking about in the RF input circuitry (at age 82 I
think I'm blessed to remember my name). If so, is it back to the way
the schematic shows now?
73,
Maynard
W6PAP
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On 2/14/25 15:07, Emanuele Girlando via groups.io wrote: Don,
the dials were (and are) installed as per Service instructions. My
sig-gen tests were done to confirm this and to align the OSC tanks.
*GUYS, I HAVE INSTALLED C62 in my S-85.*
It is a gimmick arrangement: two wires twisted together for length of
about 5 cm (a little less then a couple of inches, if I convert metric
to imperial correctly).
Results:
1. about 20dB increase in sensitivity in bands 1&2. A -70/-80dBm signal
was barely audible without C62, now I can clearly hear it at -100dBm
- GREAT!
Unfortunately this apply to higher halves of the bands only. In
lower halves the signal disappears (as before) even if forced to
-20dBm or more.
2. nothing changed in the MIX alignment and, obviously, in the ANT as
well: TRIMCAPs don't peak.
--
Emanuele (IU1KNR).
<>
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Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
A sad message to celebrate the 100th message of the thread: I'm starting to fear having to disassemble the ANT and MIX circuits from the chassis: something I would have gladly avoided doing... but I think it's the only way to test the components one by one.
--
Emanuele (IU1KNR).
|
Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Don,
the dials were (and are) installed as per Service instructions. My sig-gen tests were done to confirm this and to align the OSC tanks.
?
GUYS, I HAVE INSTALLED C62 in my S-85.
It is a gimmick arrangement: two wires twisted together for length of about 5 cm (a little less then a couple of inches, if I convert metric to imperial correctly).
Results:
- about 20dB increase in sensitivity in bands 1&2. A -70/-80dBm signal was barely audible without C62, now I can clearly hear it at -100dBm - GREAT!
Unfortunately this apply to higher halves of the bands only. In lower halves the signal disappears (as before) even if forced to -20dBm or more.
- nothing changed in the MIX alignment and, obviously, in the ANT as well: TRIMCAPs don't peak.
--
Emanuele (IU1KNR).
|
Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Hi jim, ?RE? C4 and C15 both peak nicely (by ear) at 1.4 MHz ???always good to have a verification? ? ? After looking at the S40B, we might just have to resort to the gimmick idea, but with the capacitance being between the front and rear of S1B Possibly enough capacitance? PS I tried to make this so most others could understand my thought. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of JThorusen
Sent: Friday, February 14, 2025 4:48 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!? I have been following this thread for awhile and I thought I'd add what data I can.?? I have my S-85 apart on the dining room table and I can state the following using my VNA as a signal source: 1.?? The RF amp (6SG7) is definitely in the circuit.?? When this tube is pulled, the signal goes away. 2.?? C4 and C15 both peak nicely (by ear) at 1.4 MHz. Unfortunately, the area around S1B is very crowded and visibility is poor.?? As far as I can tell, the unit is wired just as the schematic states; I'm sure there is a divergence somewhere as the circuit cannot function as drawn, but I cannot find the difference. This is probably not much help, but it is the best I can do at this time. -- don??? va3drl
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Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Greetings to the Group:
?
I have been following this thread for awhile and I thought I'd add what data I can.?? I have my S-85 apart on the dining room table and I can state the following using my VNA as a signal source:
?
1.?? The RF amp (6SG7) is definitely in the circuit.?? When this tube is pulled, the signal goes away.
2.?? C4 and C15 both peak nicely (by ear) at 1.4 MHz.
?
Unfortunately, the area around S1B is very crowded and visibility is poor.?? As far as I can tell, the unit is wired just as the schematic states; I'm sure there is a divergence somewhere as the circuit cannot function as drawn, but I cannot find the difference.
?
This is probably not much help, but it is the best I can do at this time.
?
73,
--
Jim T.
KB6GM
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Thanks Jim, will look into those areas.
Tom
Look at the audio response curve in the manual.? With the BASS switch IN, the low frequency audio is emphasized, not attenuated.??
The BASS switch in the IN position shorts out two components, CH2 and C43, I would look there first.? Perhaps there is AC being coupled into the audio circuit via CH2?? Check that the mounting screws for CH2 are making good contact with the chassis,? Corrosion between the screw head and chassis could be the problem so loosen and then tighten them.? Might as well do the same for any screw that supplies a ground or chassis connection for the audio circuit in that area of the chassis. Regards, Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
Good idea, but I pulled V12, 6SC7, and the hum remains. It is definitely in the output stages Tom
Tom Good for you Presumably, the base “In” position filters out the hum as expected… And the hum comes from upstream, maybe the AF gain? Pot area or a bad contact in the phones switch, or even before that. ?? ?
From: [email protected] [mailto:[email protected]] On Behalf Of thoyer via groups.io
Sent: Thursday, February 13, 2025 7:22 PM
To: [email protected]
Subject: [HallicraftersRadios] SX-28A Hum ? I just finished pretty much a complete overhaul of a nice condition (physically) SX-28A. Replaced just about every resistor and all caps. ? Radio is working well except for a 120hz hum. When I switch the Bass in, the hum goes away. ? Yes, there is ripple on the plates of the 6V6’s, about 6vrms, but that is there independent of the bass switch position. The output side of the HV filter is clean, no ripple. I paralleled another 47uf 450v cap across the choke input cap and there was no difference. ? I double checked the wiring against the schematic along with component values. Is the schematic correct in this area? I found once schematic error maybe there is another? ? Thoughts? ? Tom W3TA
--
don??? va3drl
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Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Emanuele, ??Oh, I should not have jumped to conclusions on a gimmick, but just maybe the band switch itself acts as a gimmick. Re the main dial, I meant this 
?
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From: [email protected] [mailto:[email protected]] On Behalf Of Emanuele Girlando via groups.io
Sent: Friday, February 14, 2025 4:23 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!? I didn't see any gimmick arrangement in my S-85. I can confirm once again C62 is not installed in my S-85 neither as a discrete component nor a a gimmick arrangement. the main tuning dial seems perfectly positioned to me. When I inject a signal from my sig-gen into the receiver, I find it exactly where I expect it to be. -- don??? va3drl
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Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
It would be interesting to have someone who has a perfectly working S-85
that aligns correctly on all bands to check for the presence of C62 or
an equivalent coupling arrangement.
Of course, most folks who have such an S-85 probably have the case in
place and it's maybe too much to ask them to pull the case to check this
out.
73,
Maynard
W6PAP
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On 2/14/25 01:22, Emanuele Girlando via groups.io wrote: Don,
I didn't see any gimmick arrangement in my S-85.
I can confirm once again C62 is not installed in my S-85 neither as a
discrete component nor a a gimmick arrangement.
the main tuning dial seems perfectly positioned to me. When I inject a
signal from my sig-gen into the receiver, I find it exactly where I
expect it to be.
--
Emanuele (IU1KNR).
<>
|
Look at the audio response curve in the manual.? With the BASS switch IN, the low frequency audio is emphasized, not attenuated.??
The BASS switch in the IN position shorts out two components, CH2 and C43, I would look there first.? Perhaps there is AC being coupled into the audio circuit via CH2?? Check that the mounting screws for CH2 are making good contact with the chassis,? Corrosion between the screw head and chassis could be the problem so loosen and then tighten them.? Might as well do the same for any screw that supplies a ground or chassis connection for the audio circuit in that area of the chassis. Regards, Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
Good idea, but I pulled V12, 6SC7, and the hum remains. It is definitely in the output stages Tom
Tom Good for you Presumably, the base “In” position filters out the hum as expected… And the hum comes from upstream, maybe the AF gain? Pot area or a bad contact in the phones switch, or even before that. ?? ?
From: [email protected] [mailto:[email protected]] On Behalf Of thoyer via groups.io
Sent: Thursday, February 13, 2025 7:22 PM
To: [email protected]
Subject: [HallicraftersRadios] SX-28A Hum ? I just finished pretty much a complete overhaul of a nice condition (physically) SX-28A. Replaced just about every resistor and all caps. ? Radio is working well except for a 120hz hum. When I switch the Bass in, the hum goes away. ? Yes, there is ripple on the plates of the 6V6’s, about 6vrms, but that is there independent of the bass switch position. The output side of the HV filter is clean, no ripple. I paralleled another 47uf 450v cap across the choke input cap and there was no difference. ? I double checked the wiring against the schematic along with component values. Is the schematic correct in this area? I found once schematic error maybe there is another? ? Thoughts? ? Tom W3TA
--
don??? va3drl
|
Interesting, I'll look into this.
Thanks,? Tom
Check whether the windings of the audio output transformer are really symmetrical. This is how the two anodes of the 6v6 are fed and the remaining hum in the end circuit is eliminated. The hum is eliminated by the two (opposing) windings. ? ? I just finished pretty much a complete overhaul of a nice condition (physically) SX-28A. Replaced just about every resistor and all caps. ? Radio is working well except for a 120hz hum. When I switch the Bass in, the hum goes away. ? Yes, there is ripple on the plates of the 6V6’s, about 6vrms, but that is there independent of the bass switch position. The output side of the HV filter is clean, no ripple. I paralleled another 47uf 450v cap across the choke input cap and there was no difference. ? I double checked the wiring against the schematic along with component values. Is the schematic correct in this area? I found once schematic error maybe there is another? ? Thoughts? ? Tom W3TA
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Good idea, but I pulled V12, 6SC7, and the hum remains. It is definitely in the output stages Tom
Tom Good for you Presumably, the base “In” position filters out the hum as expected… And the hum comes from upstream, maybe the AF gain? Pot area or a bad contact in the phones switch, or even before that. ?? ?
From: [email protected] [mailto:[email protected]] On Behalf Of thoyer via groups.io
Sent: Thursday, February 13, 2025 7:22 PM
To: [email protected]
Subject: [HallicraftersRadios] SX-28A Hum ? I just finished pretty much a complete overhaul of a nice condition (physically) SX-28A. Replaced just about every resistor and all caps. ? Radio is working well except for a 120hz hum. When I switch the Bass in, the hum goes away. ? Yes, there is ripple on the plates of the 6V6’s, about 6vrms, but that is there independent of the bass switch position. The output side of the HV filter is clean, no ripple. I paralleled another 47uf 450v cap across the choke input cap and there was no difference. ? I double checked the wiring against the schematic along with component values. Is the schematic correct in this area? I found once schematic error maybe there is another? ? Thoughts? ? Tom W3TA
--
don??? va3drl
|
Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Don,
I didn't see any gimmick arrangement in my S-85.
I can confirm once again C62 is not installed in my S-85 neither as a discrete component nor a a gimmick arrangement.
the main tuning dial seems perfectly positioned to me. When I inject a signal from my sig-gen into the receiver, I find it exactly where I expect it to be.
--
Emanuele (IU1KNR).
|
Check whether the windings of the audio output transformer are really symmetrical. This is how the two anodes of the 6v6 are fed and the remaining hum in the end circuit is eliminated. The hum is eliminated by the two (opposing) windings. ? ? I just finished pretty much a complete overhaul of a nice condition (physically) SX-28A. Replaced just about every resistor and all caps. ? Radio is working well except for a 120hz hum. When I switch the Bass in, the hum goes away. ? Yes, there is ripple on the plates of the 6V6’s, about 6vrms, but that is there independent of the bass switch position. The output side of the HV filter is clean, no ripple. I paralleled another 47uf 450v cap across the choke input cap and there was no difference. ? I double checked the wiring against the schematic along with component values. Is the schematic correct in this area? I found once schematic error maybe there is another? ? Thoughts? ? Tom W3TA
|
Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Maynard I think Emanuele alluded to the idea that he saw a gimmick across the wafer so that must be the replacement for the C62 in the S-40B. It can be hard to identify a gimmick, all depending on its details.? I am betting on the gimmick now as the mysterious missing link. ? Just maybe your question means omission of C62 or the gimmick ?? … but going one step further a poor gimmick can morph into no gimmick and too little coupling. My guess is the gimmick is there and ok.? Part of the reason is that the RF and the mixer tanks both have the same alignment problem, and Emanuele has repeated it, and the resonant curve peaks of the tanks seem to be too low in frequency, so that is still the situation. RE L6, the two coils should have quite different inductance as you said, but it would seem better for L6 not to have mutual inductance like L3., but maybe I’m missing something. We will see. ?????????? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Maynard Wright via groups.io
Sent: Thursday, February 13, 2025 9:42 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!? Don,
I think that idea has merit. I have problems with the idea that the
S-85 is intended to have nothing where C62 is located in the S-40B
because everything else looks the same on the schematics, I think.
I wonder whether accidental omission of C62 would still allow sufficient
stray coupling (think "accidental gimmick") so that the S-85 would
function but not be subject to proper alignment on Bands 1 and 2.
The two halves of L6 need not have the same inductance because an
examination of the switch shows that they are cut in separately on the
two bands and the frequency ranges involved would require different
inductances for resonance.
73,
Maynard
W6PAP ? -- don??? va3drl
|
Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Don,
I think that idea has merit. I have problems with the idea that the
S-85 is intended to have nothing where C62 is located in the S-40B
because everything else looks the same on the schematics, I think.
I wonder whether accidental omission of C62 would still allow sufficient
stray coupling (think "accidental gimmick") so that the S-85 would
function but not be subject to proper alignment on Bands 1 and 2.
The two halves of L6 need not have the same inductance because an
examination of the switch shows that they are cut in separately on the
two bands and the frequency ranges involved would require different
inductances for resonance.
73,
Maynard
W6PAP
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On 2/13/25 16:38, don Root wrote: Maynard,? ?for C62 just remove the part no, the Bakelite, and the
voltage, or chop the Cap out, leaving the short leads close together et
voila.. 2 pF.. makes the bean counters happy. ??And frustrates US to no
end.
Now why the apparent high mutual inductance for L6 ? …looking at
Emanuele’s pictures. Oh well but some interaction during alignment?
?Back to alignment.
I really hope Emanuele has triple checked that the main tuning dial has
not slipped a bit; he now doubt has, but just in case!
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Maynard Wright via
groups.io
*Sent:* Thursday, February 13, 2025 6:32 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!
Hi, Emanuele,
That's an interesting thought about a gimmick capacitor. But the parts
list for the S40B specifies C62 as 2.2mmf, 500 V, bakelite, with a
Hallicrafters part number (47A160-4).
73,
Maynard
W6PAP
--
don??? va3drl
|
Tom Good for you Presumably, the base “In” position filters out the hum as expected… And the hum comes from upstream, maybe the AF gain? Pot area or a bad contact in the phones switch, or even before that. ?? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of thoyer via groups.io
Sent: Thursday, February 13, 2025 7:22 PM
To: [email protected]
Subject: [HallicraftersRadios] SX-28A Hum? I just finished pretty much a complete overhaul of a nice condition (physically) SX-28A. Replaced just about every resistor and all caps. ? Radio is working well except for a 120hz hum. When I switch the Bass in, the hum goes away. ? Yes, there is ripple on the plates of the 6V6’s, about 6vrms, but that is there independent of the bass switch position. The output side of the HV filter is clean, no ripple. I paralleled another 47uf 450v cap across the choke input cap and there was no difference. ? I double checked the wiring against the schematic along with component values. Is the schematic correct in this area? I found once schematic error maybe there is another? ? Thoughts? ? Tom W3TA -- don??? va3drl
|
Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
Maynard,? ?for C62 just remove the part no, the Bakelite, and the voltage, or chop the Cap out, leaving the short leads close together et voila.. 2 pF.. makes the bean counters happy. ??And frustrates US to no end. Now why the apparent high mutual inductance for L6 ? …looking at Emanuele’s pictures. Oh well but some interaction during alignment? ?Back to alignment. I really hope Emanuele has triple checked that the main tuning dial has not slipped a bit; he now doubt has, but just in case! ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Maynard Wright via groups.io
Sent: Thursday, February 13, 2025 6:32 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!? Hi, Emanuele,
That's an interesting thought about a gimmick capacitor. But the parts
list for the S40B specifies C62 as 2.2mmf, 500 V, bakelite, with a
Hallicrafters part number (47A160-4).
73,
Maynard
W6PAP
-- don??? va3drl
|
I should clarify, Whether the bass is in or out, the ripple remains at the same amplitude. I just don’t hear it with the bass “in” ? Tom W3TA ?
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From: [email protected] <[email protected]> On Behalf Of thoyer via groups.io
Sent: Thursday, February 13, 2025 7:22 PM
To: [email protected]
Subject: [HallicraftersRadios] SX-28A Hum? I just finished pretty much a complete overhaul of a nice condition (physically) SX-28A. Replaced just about every resistor and all caps. ? Radio is working well except for a 120hz hum. When I switch the Bass in, the hum goes away. ? Yes, there is ripple on the plates of the 6V6’s, about 6vrms, but that is there independent of the bass switch position. The output side of the HV filter is clean, no ripple. I paralleled another 47uf 450v cap across the choke input cap and there was no difference. ? I double checked the wiring against the schematic along with component values. Is the schematic correct in this area? I found once schematic error maybe there is another? ? Thoughts? ? Tom W3TA
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Emanuele Girlando
don Root
Jim Whartenby