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Re: SX-28A Hum
¿ªÔÆÌåÓýTom, if I recall it was not fastened to the chassis¡ at least in the same way. ?If the power transformer is near by the choke, it¡¯s flux can/might? use a bit of the chassis and the choke could pick it up from the flux in the chassis. For that I would try removing steel fastening on one hold down point or both and grounding the core for safety at one point only or separately.? You could Put a little space under the choke as a test? ? But it is also possible that wires from the on/of switch run too close to the BASE ?switch. ? If you want more stable scope traces sync to the ¡°line¡± or whatever it might be called now. ? From: [email protected] [mailto:[email protected]] On Behalf Of thoyer via groups.io
Sent: Wednesday, February 19, 2025 12:52 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum ? Interesting Don........ ? When I replaced the choke, CH2, this all went away so I don't know how it would be related to the power xfmr? ? Tom ? On Wednesday, February 19, 2025 at 12:31:39 PM EST, don Root <drootofallevil@...> wrote: ? ? Tom and/or anybody still tuned in. Still looking for what really failed and how. For anyone wondering about the details and possible source, I copied a bit of your first Video so I could take a closer look. I see 60 Hz and strong third harmonics, and no visible high harmonics. It reminds me of core saturation. Power transformer magnetics and primary is the only source I can think of. Any comments?
-- don??? va3drl |
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Re: SX-28A Hum
¿ªÔÆÌåÓýTom and/or anybody still tuned in. Still looking for what really failed and how. For anyone wondering about the details and possible source, I copied a bit of your first Video so I could take a closer look. I see 60 Hz and strong third harmonics, and no visible high harmonics. It reminds me of core saturation. Power transformer magnetics and primary is the only source I can think of. Any comments?
-- don??? va3drl |
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Re: SR-500 Tornado
¿ªÔÆÌåÓý
Hi Scott,
The Tornado (SR-500) is an excellent tri-bander. It is a single conversion receiver that performs better than a lot of dual?conversion rigs. With its 250 to 300 watt output it will punch through the noise. The SR-500 is actually an SR-160 with a beefed up
PA subsystem and a power supply providing higher voltages.
The 8236 tubes ARE a problem. Although these are magnificent tubes, with solid carbon block plates, they do occasionally go bad. There are not many good sources for them. When you do run across them there is no guarantee that?they will be matched. Matching
is key to proper operation of the PA.?
The 6DQ5 is a direct replacement for?the 8236. There is a problem with the height of 6DQ5. They come in various?sizes and even with the shortest tubes you need to dimple the PA gage cover.?
The final Achilles heel is the vfo. The 500, like all the SR series rigs, are three times older than the shelf life of its temperature compensating capacitors. This is not a difficult problem to solve, replace C129 NPO and C133 N470.
I hope I have not scared you off the quest for a Tornado. But all ventage rigs require a little TLC.
I have written a repair manual for the SR-500 Tornado. It is a no cost download at:
Good luck with your quest, 73.
Walt Cates, WD0GOF
?
From: [email protected] <[email protected]> on behalf of Scott WA9WFA via groups.io <whitebear1122@...>
Sent: Wednesday, February 19, 2025 12:21 AM To: [email protected] <[email protected]> Subject: [HallicraftersRadios] SR-500 Tornado ?
Hi, Lately I¡¯ve been waxing nostalgic about the old Hallicrafters transceivers. ?A friend loaned me his SR-160 for several months back in 1971 while I was in Senior in High School and I used it for that
summer before heading off to the Vietnam War. ? It was a wonderful transceiver! ?
The premium Hurricane, Cyclone, and Tornado have fascinated me for many years but I never pursued them during my collecting years. ?The collecting years are long over and I¡¯ve sold 99% of my collection with only a few left, but I¡¯m still
intrigued by those premium Halli transceivers.?
Maybe I need another one just to enjoy the nostalgia it gives.?I¡¯m thinking of buying a Tornado for my one last remaining SSB tube transceiver.
The Hurricane and Cyclone scare me in terms of big size and complexity of repair. ?What about the Tornado? ?Do you Tornado owners find them easy or hard to repair? ?Are final amplifier tubes available or do you have to rewire
the socket for something else? ?
What do you Tornado owners think of them? ? Do you know of any working one¡¯s for sale?
Thanks. ?73, Scott WA9WFA
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Re: SX-28A Hum
Tom Didn't you report that you replaced the 4H choke on Monday and that there was still hum?? What changed? Looking at your videos, I notice that the frequency readout on the o'scope does not agree with the displayed waveform.? The evanescent waveform looks to me like an oscillation.? There is a reduction in amplitude in several peaks then it returns to the initial amplitude.? It looks like an analog counting circuit.? Strange. If the hum returns, I would check all of the circuit ground connections and solder them to the chassis.? I agree that there might be a strange feedback path causing the oscillation.? I had a Gonset G-63 receiver that I recapped but could not do a successful alignment.? I soldered all of the tube sockets and other terminals used for grounds and that cured the problem. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Tuesday, February 18, 2025 at 07:57:31 PM CST, thoyer via groups.io <thoyer1@...> wrote:
Ok folks, I found the culprit ¨C that dog gone choke! I replaced it with a 4hy one from an R390A AF deck and the hum is gone. I laid it in the chassis, insulated from the circuits and wired it in with short leads. Actually the hum is barely there, you have to put your ear up to the speaker to get a hint of it, but this is the level I¡¯d expect from an old radio like this. ? There is a small difference in chokes in that the original is, I believe, 220 ohms and the Collins one is 110 ohms. I¡¯ll have to try to locate one that fits the mounting holes. ? For now, I think we can put this head scratcher to rest. ? I appreciate all of the thought and input from everyone, I definitely learned something about this circuit which is always a good thing. Problem is will I remember it next week¡¡¡¡. ? ? Thank you all, ? Tom W3TA ? From: [email protected] <[email protected]> On Behalf Of thoyer via groups.io
Sent: Tuesday, February 18, 2025 6:08 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum ? Jacques, ? I ¡°may¡± guilty of not returning caps to the same ground as original¡¡¡¡ I need to look into this. I took lots of before and after pics so I should be able to confirm ? Tom ? From: [email protected] <[email protected]> On Behalf Of Jacques_VE2JFE via groups.io ? Let¡¯s resume the case?: Tom pulled the 6SC7 and the ¡°hum¡± remained. He shorted the two 6V6 grids to GND and the hum disappeared. No hum when the ¡°bass¡± switch is in the IN position (both plate loads of the 6SC7 equal and CH2 + C43 shorted). Hum present when the ¡°bass¡± sw in OUT position. The ¡°hum¡± is at 60Hz¡ ? Which suspects remains ?? Does the C44 is ¡°grounded¡± at the same place than the filaments of the 6V6s and this connection is resistive ?? Clue: when the driver stage is ¡°balanced¡± plates loads wise, no hum. When it is not: hum ! Note here that the 4H. inductor reactance at 60Hz is only 1500 ohms¡ and that the C43 is practically an open circuit at 60 Hz. Could it be that the 60Hz injection point is the C44 grounding lug ? ? My two SX-28As are too far to be quickly reached. But If I manage to dig the ¡°never touched¡± one out of the storage during the next weekend, I can check how it is wired. Keep thinking¡. ? And about the meaning of the ¡°Bass¡± switch: when it is IN, the bass is ENABLED (literally, ¡°bass¡± is in). When out: bass is out (DISABLED). CH2 ¨C C43 forms a resonant circuit at ~ 1.1kHz. The obvious intent is to ¡°tailor¡± an audio bandpass response for voice frequencies (300Hz ¨C 3kHz) ? ? ? ? ? 73, Jacques, VE2JFE in Montreal ? Gents, dunno about all that, but why the no hum in the In position? And when base is boosted? ??
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Re: SX-28A Hum
Tom Didn't you report that you replaced the 4H choke on Monday and that there was still hum?? What changed? Looking at your videos, I notice that the frequency readout on the o'scope does not agree with the displayed waveform.? The evanescent waveform looks to me like an oscillation.? There is a reduction in amplitude in several peaks then it returns to the initial amplitude.? It looks like an analog counting circuit.? Strange. If the hum returns, I would check all of the circuit ground connections and solder them to the chassis.? I agree that there might be a strange feedback path causing the oscillation.? I had a Gonset G-63 receiver that I recapped but could not do a successful alignment.? I soldered all of the tube sockets and other terminals used for grounds and that cured the problem. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Tuesday, February 18, 2025 at 07:57:31 PM CST, thoyer via groups.io <thoyer1@...> wrote:
Ok folks, I found the culprit ¨C that dog gone choke! I replaced it with a 4hy one from an R390A AF deck and the hum is gone. I laid it in the chassis, insulated from the circuits and wired it in with short leads. Actually the hum is barely there, you have to put your ear up to the speaker to get a hint of it, but this is the level I¡¯d expect from an old radio like this. ? There is a small difference in chokes in that the original is, I believe, 220 ohms and the Collins one is 110 ohms. I¡¯ll have to try to locate one that fits the mounting holes. ? For now, I think we can put this head scratcher to rest. ? I appreciate all of the thought and input from everyone, I definitely learned something about this circuit which is always a good thing. Problem is will I remember it next week¡¡¡¡. ? ? Thank you all, ? Tom W3TA ? From: [email protected] <[email protected]> On Behalf Of thoyer via groups.io
Sent: Tuesday, February 18, 2025 6:08 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum ? Jacques, ? I ¡°may¡± guilty of not returning caps to the same ground as original¡¡¡¡ I need to look into this. I took lots of before and after pics so I should be able to confirm ? Tom ? From: [email protected] <[email protected]> On Behalf Of Jacques_VE2JFE via groups.io ? Let¡¯s resume the case?: Tom pulled the 6SC7 and the ¡°hum¡± remained. He shorted the two 6V6 grids to GND and the hum disappeared. No hum when the ¡°bass¡± switch is in the IN position (both plate loads of the 6SC7 equal and CH2 + C43 shorted). Hum present when the ¡°bass¡± sw in OUT position. The ¡°hum¡± is at 60Hz¡ ? Which suspects remains ?? Does the C44 is ¡°grounded¡± at the same place than the filaments of the 6V6s and this connection is resistive ?? Clue: when the driver stage is ¡°balanced¡± plates loads wise, no hum. When it is not: hum ! Note here that the 4H. inductor reactance at 60Hz is only 1500 ohms¡ and that the C43 is practically an open circuit at 60 Hz. Could it be that the 60Hz injection point is the C44 grounding lug ? ? My two SX-28As are too far to be quickly reached. But If I manage to dig the ¡°never touched¡± one out of the storage during the next weekend, I can check how it is wired. Keep thinking¡. ? And about the meaning of the ¡°Bass¡± switch: when it is IN, the bass is ENABLED (literally, ¡°bass¡± is in). When out: bass is out (DISABLED). CH2 ¨C C43 forms a resonant circuit at ~ 1.1kHz. The obvious intent is to ¡°tailor¡± an audio bandpass response for voice frequencies (300Hz ¨C 3kHz) ? ? ? ? ? 73, Jacques, VE2JFE in Montreal ? Gents, dunno about all that, but why the no hum in the In position? And when base is boosted? ??
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Re: SX-28A Hum
¿ªÔÆÌåÓýRichard I just replied about that now. Your wording might be better than mine.. well not quite , you propose magnetic coupling thru the air?, I was thinking the steel chassis might couple depending on the mounting ¡°±ô±ð²µ²õ¡±. ? From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow via groups.io
Sent: Tuesday, February 18, 2025 9:54 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum ? Once the choke is removed from the chassis can you investigate if Ok folks, I found the culprit ¨C that dog gone choke! I replaced it with -- -- don??? va3drl |
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Re: SX-28A Hum
¿ªÔÆÌåÓýTom, that is good, but ?that choke is always zipping up and down wrt ground.? Is it possible that the mounting to the chassis makes the difference. As in magnetic coupling to the power transformer? At the moment I don¡¯t see just how that would do it, but I wonder is the original is partly isolated, would it be better. Or how is that choke failing? Insulation to the core and ground. ? From: [email protected] [mailto:[email protected]] On Behalf Of thoyer via groups.io
Sent: Tuesday, February 18, 2025 8:57 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum ? Ok folks, I found the culprit ¨C that dog gone choke! I replaced it with a 4hy one from an R390A AF deck and the hum is gone. I laid it in the chassis, insulated from the circuits and wired it in with short leads. Actually the hum is barely there, you have to put your ear up to the speaker to get a hint of it, but this is the level I¡¯d expect from an old radio like this. ? There is a small difference in chokes in that the original is, I believe, 220 ohms and the Collins one is 110 ohms. I¡¯ll have to try to locate one that fits the mounting holes. ? For now, I think we can put this head scratcher to rest. +++++++++ ? ? -- don??? va3drl |
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Re: SX-28A Hum
¿ªÔÆÌåÓýHi Mike, then the question becomes which loop?? They use/assume ?the chassis as if it has zero resistance and zero self inductance and zero mutual inductance. We just hope there was some method hidden in the madness when they designed it so critical areas are mostly isolated. It must be full of UNMARKED small loops It is a mystery to me how you don¡¯t run into bad coupling. And like it was said I think, take a heater to a ground point, add a signal ground to the same point, and wait for corrosion to add some common resistance et voila a hum generator in the grid circuit. Don¡¯t know if that is a real loop, but you can predict that those can go bad, and you can usually see them as possible hot spots.? Probably Jacques is talking about that sort of thing, but I have not gotten that far yet. ???? ? From: [email protected] [mailto:[email protected]] On Behalf Of Mike Langner via groups.io
Sent: Tuesday, February 18, 2025 8:56 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum ? I received a direct email from a member of this reflector asking what my comments about ground loops in an amplifier chassis had to do with the SX-28 hum discussion. -- don??? va3drl |
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Re: SX-28A Hum
¿ªÔÆÌåÓýDang ! Could you measure a leakage between the winding of the ¡°original¡± choke and it¡¯s core ?? Happy that this ¡°mystery¡± is solved ! ? 73, Jacques, VE2JFE in Montreal ? De?: [email protected] <[email protected]> De la part de thoyer via groups.io ? Ok folks, I found the culprit ¨C that dog gone choke! I replaced it with a 4hy one from an R390A AF deck and the hum is gone. I laid it in the chassis, insulated from the circuits and wired it in with short leads. Actually the hum is barely there, you have to put your ear up to the speaker to get a hint of it, but this is the level I¡¯d expect from an old radio like this. ? There is a small difference in chokes in that the original is, I believe, 220 ohms and the Collins one is 110 ohms. I¡¯ll have to try to locate one that fits the mounting holes. ? For now, I think we can put this head scratcher to rest. ? I appreciate all of the thought and input from everyone, I definitely learned something about this circuit which is always a good thing. Problem is will I remember it next week¡¡¡¡. ? ? Thank you all, ? Tom W3TA ? From: [email protected] <[email protected]> On Behalf Of thoyer via groups.io
Sent: Tuesday, February 18, 2025 6:08 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum ? Jacques, ? I ¡°may¡± guilty of not returning caps to the same ground as original¡¡¡¡ I need to look into this. I took lots of before and after pics so I should be able to confirm ? Tom ? From: [email protected] <[email protected]> On Behalf Of Jacques_VE2JFE via groups.io ? Let¡¯s resume the case?: Tom pulled the 6SC7 and the ¡°hum¡± remained. He shorted the two 6V6 grids to GND and the hum disappeared. No hum when the ¡°bass¡± switch is in the IN position (both plate loads of the 6SC7 equal and CH2 + C43 shorted). Hum present when the ¡°bass¡± sw in OUT position. The ¡°hum¡± is at 60Hz¡ ? Which suspects remains ?? Does the C44 is ¡°grounded¡± at the same place than the filaments of the 6V6s and this connection is resistive ?? Clue: when the driver stage is ¡°balanced¡± plates loads wise, no hum. When it is not: hum ! Note here that the 4H. inductor reactance at 60Hz is only 1500 ohms¡ and that the C43 is practically an open circuit at 60 Hz. Could it be that the 60Hz injection point is the C44 grounding lug ? ? My two SX-28As are too far to be quickly reached. But If I manage to dig the ¡°never touched¡± one out of the storage during the next weekend, I can check how it is wired. Keep thinking¡. ? And about the meaning of the ¡°Bass¡± switch: when it is IN, the bass is ENABLED (literally, ¡°bass¡± is in). When out: bass is out (DISABLED). CH2 ¨C C43 forms a resonant circuit at ~ 1.1kHz. The obvious intent is to ¡°tailor¡± an audio bandpass response for voice frequencies (300Hz ¨C 3kHz) ? ? ? ? ? 73, Jacques, VE2JFE in Montreal ? Gents, dunno about all that, but why the no hum in the In position? And when base is boosted? ??
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Re: SX-28A Hum
¿ªÔÆÌåÓýHi Don, ? Yeah, there is a misprint in the TM11-874 schematic. The 180M (180K) is the value of R39 (see parts list), but there is another ¡°270M¡± in excess just below it¡. ? 73, Jacques, VE2JFE in Montreal ? De?: [email protected] <[email protected]> De la part de don Root ? Jacques, I was going thru your recent post and started turning into a pretzel;? ?adding and then removing a resistor. See my ¡°side-by-each¡± . ????180 ¡°M?¡± but no squiggle ? |
don Root
waltcates
Jim Whartenby
Jacques_VE2JFE