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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!
开云体育Hello Emanuele, One time again, I performed some calculations from your test results below. IF there is no error in the C7A capacitor and L3 sections measurements, your test results constantly shows an effect of EXCESS capacitance in the tested antenna circuits. Could that be induced by the test setup you use ?? The attached .pdf contains the calculated “excess capacitance” values (that are not constant, btw). And also the kind of test setup I will use to perform such tests. ? Maybe I missed something from the (very) long thread of exchanges about this problem, but the test setup you used is still not clear to me. I just want to mention that measuring the resonant frequency of a parallel circuit requires high impedance from both the RF source used and the instrument displaying the result. ? As one of my colleagues already mentioned: “Nothing is more useful than a good theory”. And I still believe that it is true. ? Let us know ! ? 73, Jacques, VE2JFE in Montreal ? Some additional info: disconnecting BS variable condenser doesn't change things significantly. Here are measurements (ANT circuit only): ? ? I then disconnected C33 from V1 pin4 and moved the probe to C3 but, again, nothing significant happens. Now the ANT circuit is completely alone and ... still resonating too low. I also tried to switch the input connection between; RTMA, a 0.01uF cap, pure induction (air). The signal levels change, but the peak is steady at the wrong values. ? Here you can see the variables: I cannot see any sign indicating not being Halli's originals. ? The last resort idea is to check wiring and all part numbers of my not working ANT circuit against someone else working one. ? -- 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!
Some additional info:
disconnecting BS variable condenser doesn't change things significantly. Here are measurements (ANT circuit only):
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I then disconnected C33 from V1 pin4 and moved the probe to C3 but, again, nothing significant happens.
Now the ANT circuit is completely alone and ... still resonating too low.
I also tried to switch the input connection between; RTMA, a 0.01uF cap, pure induction (air). The signal levels change, but the peak is steady at the wrong values.
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Here you can see the variables: I cannot see any sign indicating not being Halli's originals.
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The last resort idea is to check wiring and all part numbers of my not working ANT circuit against someone else working one.
Should anyone else had an S-85 open on the ?bench, your input would be greatly appreciated (Jim, are you still there?). ?
--
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!
开云体育Emanuele, as you seek out more and more long-shot ideas for your original problem set, sometime you might contemplate the probability that an “almost same” C7 ?somehow managed to get the right S-85 part number put on it [ but only the min capacitance was not as low] and then ?put in your radio, and perhaps it got passed along as a shelf queen all this time, passing from one SWL to another. Without having Jim undo his wires maybe you two can visually measure/compare the rotor to stator gaps when wide open or something? ? -- 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!
开云体育Emanuele the? side view of L3, and L6 shows more spacing between coils than the earlier? “almost end views” did, and consequently in my mind, the mutual coupling and trimmer tuning interaction will not be much. ? ? Some bug has me, but I am up for a bit.. staring at C33 , which is needed to let the AVC control the RF grid, while allowing RF to also couple from the left. Since C33 is hung on the tuning condensers and switch the other end of it will need to maintain High resistance 1 Meg ofr R1 ????.very long shot but . ?? ? Whaterever it is that is wonky, it does the same thing to the RF and Mixer. ??I keep wondering what would happen with the BS wires lifted ? -- don??? va3drl |
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Re: SX-28A Hum
开云体育Hello Tom, I believe that the “bubbles” in the original choke encapsulation just came from when the coal tar was poured in during manufacture. There is no possibility that the part “overheated” IMHO. For the suitability of the replacements: as the 4Hy choke from the R-390A Audio Deck you used only have 110 ohms of internal resistance, it will be 100% OK to add a 110 ohms resistor in series with it to “emulate” the 220 ohms of the original part. I also checked if any recent manufacture Hammond choke can be used, but no luck there: the smallest 4Hy one have a 300 ohms internal resistance, and that value cannot be “reduced” in any way. The other 4Hy parts are really too big for the task, not speaking of the cost… ? 73, Jacques, VE2JFE in Montreal ? Hi Jim,? ? Well that's not what I wanted to hear, but I understand. I'm actively looking for a suitable replacement choke. The on I substituted in was all I had laying around and figured it would be good for a test. ? The original choke is encapsulated and the bottom side shows bubbles in that encapsulation. I have designed products that have used encapsulation in the past and have seen these bubbles before, they are usually caused by the part overheating. ? Hopefully the attached image shows. ? Tom |
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Re: SX-28A Hum
开云体育Jim, that waveform is what I previously commented on. Looks like a base frequency of 60 with third harmonic. ?the 3rd harmonic is generated by the PT magnetizing current and it ?along with the 60 HZ coupled ?to wires in the choke circuit somehow; wiring being most likely. The location of the choke ?makes it unlikely that it is directly from the transformer. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Wednesday, February 19, 2025 10:14 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum ? I am not sure that the problem is resolved.? CH2 was replaced with a similar value choke with less winding resistance so it will have higher Q.? Higher Q will affect the audio filter curve so there will most likely be more ripple in the audio bandpass in the bass out switch position.? This may not be that noticeable to the ear but the scope will see it. ? In Tom's first video, at about the 45 second mark, the scope shows a strange waveform.? The main peaks are of a 60 cycle waveform.? The center peak is at 120 cycle but it's peak is negative, the two remaining peaks are at 240 hertz and positive.? There must be some nonlinearity to cause these harmonics to be generated.? This nonlinearity is acting like a diode and causing the second and forth harmonics of the 60 cycle waveform. Regards, Jim ? ? -- 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!
Jim, we were working on the same idea.
Here is my resonance frequencies table give the measured values. I added 10pF to count for min capacitance of the BS variable (estimated) as per Don's suggestion.
Rounding a part, it fully matches with your calculation.
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Having L3 out of circuit I was able to detect the ACTUAL signal paths in bands 1&2 (neither theoretical nor from schematic: ACTUAL).
I think they are identical to what you expressed in words and, at the end, matches with Don's drawings (many posts ago).
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Give this arrangement it appears clear to me that the alignment sequence is very important as setting on band 2 interacts with setting in band 1 and vice versa.
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Now I need to hunt for the hidden capacity that's moving all responses down,? ...but I really can't find it.
--
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!
开云体育Jacques, it is not much maybe but where is the min cap of the BS? What is the dial frequency at the very top of the band [min cap] ?is !.6kc ?really min capacitance. Agree, even with a small change it still looks like come hidden cap ???? Emanule re Jim’s .. at 1360 or 1380 there is no breathing room on the trimmer like one would expect. ? Also many variable caps have the min cap below 10% of the max, so we can wonder what this one was intended to be ? From: [email protected] [mailto:[email protected]] On Behalf Of Jacques_VE2JFE via groups.io
Sent: Thursday, February 20, 2025 10:57 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! Importance: High ? Hi Emanuele, ? From your measurements: BAND 1: C7A = 450pF, L3(C&D) = 200?H Fr = 530.5kHz (1/(6.2832 x SQRT(L x C))) C7A = 50pF, L3(C&D) = 200?H Fr = 1591.5 kHz ? BAND 2: C7A = 450pF, L3(A&B) = 26?H Fr = 1.47 MHz C7A = 50pF, L3(A&B) = 26?H Fr = 4.414 MHz ? From a mathematical point of view, that should work on both bands, or be very close to ! Unless there is a hidden capacitance in the assembly somewhere, like a connecting wire that should stand in free air, but that is pushed close to the GND along it’s path instead.? (I have seen that before: too long story to tell here). Hard to verify because the radio is not right in front of me …. I also believe that the schematic is right: on band 2, the A+B section of L3 is connected to C7A, but the antenna signal is fed to L3 C+D and coupled using mutual inductance between the coils. On band 1, L3 C+D section is connected to C7A, antenna signal fed to L3 A+B section with a 1k resistor in series and fed by mutual inductance again. I believe that the 1k resistor is there to “balance” the Band 1 sensitivity to the one of the other bands (more or less). ? Sorry to repeat feats or opinions that were mentioned before on the thread, but I caught this boat late… ? 73, Jacques, VE2JFE in Montreal ?
-- 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!
开云体育Hi Emanuele, ? From your measurements: BAND 1: C7A = 450pF, L3(C&D) = 200?H Fr = 530.5kHz (1/(6.2832 x SQRT(L x C))) C7A = 50pF, L3(C&D) = 200?H Fr = 1591.5 kHz ? BAND 2: C7A = 450pF, L3(A&B) = 26?H Fr = 1.47 MHz C7A = 50pF, L3(A&B) = 26?H Fr = 4.414 MHz ? From a mathematical point of view, that should work on both bands, or be very close to ! Unless there is a hidden capacitance in the assembly somewhere, like a connecting wire that should stand in free air, but that is pushed close to the GND along it’s path instead.? (I have seen that before: too long story to tell here). Hard to verify because the radio is not right in front of me …. I also believe that the schematic is right: on band 2, the A+B section of L3 is connected to C7A, but the antenna signal is fed to L3 C+D and coupled using mutual inductance between the coils. On band 1, L3 C+D section is connected to C7A, antenna signal fed to L3 A+B section with a 1k resistor in series and fed by mutual inductance again. I believe that the 1k resistor is there to “balance” the Band 1 sensitivity to the one of the other bands (more or less). ? Sorry to repeat feats or opinions that were mentioned before on the thread, but I caught this boat late… ? 73, Jacques, VE2JFE in Montreal ? ? Jim, great job! Don, remember: 1600-500=1100 so we have 110KHz/DIV; 1600-220=1380 .. close enough. So Jim's peak stay exactly where it should: dial @1400KHz !! peak at 1380KHz. His tank works as expected! Jacques, C7 is halli original with the correct prt. no. 048-300341. It measures 50-450pF (LCR). L3 has nothing, null, nope, vacuum inside. NO CORE. L3 coils as measured by the LCR: the first coil (pins A and B) measures 26uH, while the second (pins C and D) measures 200uH. ? -- Emanuele (IU1KNR). _._,_._,_ |
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Re: SR-500 Tornado
开云体育
There is no socket conversion needed. The 6DQ5 is a direct "plug and play".
Walt Cates, WD0GOF
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From: [email protected] <[email protected]> on behalf of Scott WA9WFA via groups.io <whitebear1122@...>
Sent: Thursday, February 20, 2025 12:17 AM To: [email protected] <[email protected]> Subject: Re: [HallicraftersRadios] SR-500 Tornado ?
Thank you Walt for your SR-160 and SR-500 information, weak points, and the finals. ?I think I've read an early post of yours talking about converting the 8236 tube socket to 6DQ5. ?I didn't have a clue about tube height though. ?Also didn't know about
the temperature compensation capacitor failure. ?I will download your SR-500 repair manual. ?I've seen your other repair manuals before and they are a godsend! ?
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I'm going to keep my eyes open for an SR-500 Tornado to satisfy a nostalgic urge for the SR-160 and the long time desire to own one of the premium transceivers like the Tornado, Cyclone, Hurricane. ? If someone on the list knows of a nice condition Tornado
for sale, I'd appreciate hearing about it. ?
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Thanks.. ?73, Scott WA9WFA
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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!
Jim, great job!
Don, remember: 1600-500=1100 so we have 110KHz/DIV; 1600-220=1380 .. close enough. So Jim's peak stay exactly where it should: dial @1400KHz !! peak at 1380KHz. His tank works as expected!
Jacques, C7 is halli original with the correct prt. no. 048-300341. It measures 50-450pF (LCR).
L3 has nothing, null, nope, vacuum inside. NO CORE.
L3 coils as measured by the LCR: the first coil (pins A and B) measures 26uH, while the second (pins C and D) measures 200uH.
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--
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!
开云体育Jim? thanks from us! so both are similar, peaking too low Poor low band may be due to No “C 62” as in the S40B ?? ? From: [email protected] [mailto:[email protected]] On Behalf Of JThorusen
Sent: Wednesday, February 19, 2025 9:51 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! ? Greetings to the Group: ? ?? I attempted to replicate Emanuele's measurement of the RF tank circuit.?? This required that I construct an RTMA dummy antenna, which turned out to be a bit of a chore; I had to make the 20 uH coil as I didn't have anything close in stock.?? Since Emanuele used a spectrum analyzer with tracking generator, I decided to do the same.?? The tracking generator output was connected to the antenna terminals (with the low side jumper to ground in place) through the RTMA dummy antenna.?? The signal was taken from the RF amplifier (V1, 6SG7) control grid, pin 4 with a 10:1 oscilloscope probe.?? The receiver main tuning dial was set to 1.4 MHz.?? The tracking generator level was set to 0 dbm to obtain adequate signal for display.?? The sweep range was from .5 MHz to 1.6 MHz.?? 10 db/division vertical scale. ? Here are the results: ? This is the response with C4 set to minimum capacity. ? This is the response with C4 set to maximum capacity. ? ?? Incidentally, my receiver also displays considerable sensitivity change over the broadcast band.?? At the high end, there is considerable 60Hz hash and noise as one would expect in a suburban environment.?? As one tunes to the bottom of the band, the receiver becomes virtually quiet.?? I live a fair distance from the nearest AM broadcast station and I was unable to hear anything on the pair of clip leads I was using for an antenna; only the above mentioned noise. ? 73, -- Jim T. _._,_._,_ -- don??? va3drl |
Jacques_VE2JFE
Emanuele Girlando
don Root
waltcates