Re: SX-110 2nd IF Circuit Design
When did the SX 42 come on the market?? Hallicrafters advertised it as the first really new post war receiver.? FM broadcasting began experimentally in 1936 according to FCC records .? By 1946 there were about 25 stations.? The FCC decided to move the FM band to 88 to 108 mhz starting in 1946, requiring all existing stations to change by 1948.? Evidently both bands were in use during the changeover period.? So, if the SX 42 was released in 1946 it likely accommodated both bands. Since the change had been proposed and discussed for some time in advance it seems unlikely many receivers were made without the new band.? They would have been obsolete immediately.? May some.prototypes were made.? It's interesting thT the S 36 covered both bands although the high band was not assigned to broadcasting at the time. The history of FM is filled with controversy.? ?Makes interesting reading.? FM was not profitable until the introduction of compatible stereo and the FCC regulation requiring dual AM/FM receivers .? There was just not a large enough potential audience to support it.
toggle quoted message
Show quoted text
-------- Original message -------- From: "KW4H via groups.io" <reedsteve@...> Date: 10/31/22 2:18 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
On the SX-42:? Osterman’s book indicates that there were several circuit changes during the production years of this model.? One of the back stories appears to be what happened with FM radio.? From 1936-46, FM was in the 42 – 50 Mhz band.? However, the FCC required FM stations to move to the new frequencies of 88 – 108 MHz by 1948.? In response, Hallicrafters added a sixth band, to bring the coverage up to 110 MHz.? What’s really confusing is that the model number stayed exactly the same despite all the circuit changes. ? 73 – Steve, KW4H ? Jacques; Holy Moly! as we used to say, no wonder we? are in no-mans’ land. Continuing the SX-42 diversion…I saw some of the detailed changes sheets on the BAMA site ?too, and they seem to address much of this. It seems clear that at some point there were significant changes beginning at the secondary of the 3rd IF transformer and ongoing, and the major rev must be adding that switch so that both the AM and FM go thru the first 7H7, whatever it is really doing. Wonder why the change/changes?? Makes one think the original circuit did not have enough amplification on AM. ?? I am still trying to make sense of the circuit; is ?the 7H7 really amplifying or what? Getting back to Sterves Original question about why one tube, not the other: One wonders Why use a Loctal when most are octals? The S-47 uses a 6SG7 in the same spot? but is called ??“FM 3RD IF AMP –AM DET” and it is produced at the same time. How is your band switch doing? Don VA3DRL ? ? Hi Don, ? The different produced versions of the SX-42 made me scratch my head big time… Let’s say that in the first versions (according to the schematic 89D210) the first 7H7 is identified as a “1st 濒颈尘颈迟别谤”. Probably because it is used only for the 10.7 MHz IF signal and then feeds the 2nd 7H7 tube identified as the “2nd limiter and 10.7 MHz AM detector”. The 455 kHz signal from the 3rd IF transformer is not coupled to the 1st 7H7 but applied to half of a 6H6 used as a detector, the other half of the same tube supporting the Noise Limiter function. ? In the late production versions (according to the 89D257 schematic) both the 455 kHz and 10.7 MHz signals are applied to the first 7H7 tube grid, and it’s designation was changed to “3rd 滨贵”. Both 455 kHz and 10.7 MHz AM signals are then “detected” by the second 7H7 tube (control grid to cathode) and the right part of the 6H6, used as a detector in the first versions, is completely disconnected. ? And A LOT of components values and circuitry topology changed between the first and the last SX-42 made. The one I restored last spring was something of a mix between the first and the last versions already (stamped May 12, 1947) and was more or less conform to the XXXX production run, so I decided to rebuild it to be compliant to the schematic 89D257E. ? Let’s figure here that there was 20 engineering changes applied successively to the production runs X, XX, XXX, XXXX and 1, updating the related schematics from 89D210 to 89D210K. Then the 89D257 come, with more engineering changes creating versions from A to G. The 89D257F required a change to the SW 1 (the Band switch), sections K and KK, and this is why I had not been able to implement this one. But the Rev. G change, which added a 6.8 ohms resistor (R108) in series with the 6H6 noise limiter heater was doable. ? At the end, I do not know if my own “version” of the SX-42 work better (or worse) than any other… But, at least, it works on all bands and modes ! ? 73, Jacques, VE2JFE in Montreal ? Jacques ?and the gang Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp? don
|
Re: SX-110 2nd IF Circuit Design
On the SX-42:? Osterman’s book indicates that there were several circuit changes during the production years of this model.? One of the back stories appears to be what happened with FM radio.? From 1936-46, FM was in the 42 – 50 Mhz band.? However, the FCC required FM stations to move to the new frequencies of 88 – 108 MHz by 1948.? In response, Hallicrafters added a sixth band, to bring the coverage up to 110 MHz.? What’s really confusing is that the model number stayed exactly the same despite all the circuit changes. ? 73 – Steve, KW4H ? Jacques; Holy Moly! as we used to say, no wonder we? are in no-mans’ land. Continuing the SX-42 diversion…I saw some of the detailed changes sheets on the BAMA site ?too, and they seem to address much of this. It seems clear that at some point there were significant changes beginning at the secondary of the 3rd IF transformer and ongoing, and the major rev must be adding that switch so that both the AM and FM go thru the first 7H7, whatever it is really doing. Wonder why the change/changes?? Makes one think the original circuit did not have enough amplification on AM. ?? I am still trying to make sense of the circuit; is ?the 7H7 really amplifying or what? Getting back to Sterves Original question about why one tube, not the other: One wonders Why use a Loctal when most are octals? The S-47 uses a 6SG7 in the same spot? but is called ??“FM 3RD IF AMP –AM DET” and it is produced at the same time. How is your band switch doing? Don VA3DRL ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Jacques_VE2JFE
Sent: Monday, October 31, 2022 12:21 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
Importance: High? Hi Don, ? The different produced versions of the SX-42 made me scratch my head big time… Let’s say that in the first versions (according to the schematic 89D210) the first 7H7 is identified as a “1st 濒颈尘颈迟别谤”. Probably because it is used only for the 10.7 MHz IF signal and then feeds the 2nd 7H7 tube identified as the “2nd limiter and 10.7 MHz AM detector”. The 455 kHz signal from the 3rd IF transformer is not coupled to the 1st 7H7 but applied to half of a 6H6 used as a detector, the other half of the same tube supporting the Noise Limiter function. ? In the late production versions (according to the 89D257 schematic) both the 455 kHz and 10.7 MHz signals are applied to the first 7H7 tube grid, and it’s designation was changed to “3rd 滨贵”. Both 455 kHz and 10.7 MHz AM signals are then “detected” by the second 7H7 tube (control grid to cathode) and the right part of the 6H6, used as a detector in the first versions, is completely disconnected. ? And A LOT of components values and circuitry topology changed between the first and the last SX-42 made. The one I restored last spring was something of a mix between the first and the last versions already (stamped May 12, 1947) and was more or less conform to the XXXX production run, so I decided to rebuild it to be compliant to the schematic 89D257E. ? Let’s figure here that there was 20 engineering changes applied successively to the production runs X, XX, XXX, XXXX and 1, updating the related schematics from 89D210 to 89D210K. Then the 89D257 come, with more engineering changes creating versions from A to G. The 89D257F required a change to the SW 1 (the Band switch), sections K and KK, and this is why I had not been able to implement this one. But the Rev. G change, which added a 6.8 ohms resistor (R108) in series with the 6H6 noise limiter heater was doable. ? At the end, I do not know if my own “version” of the SX-42 work better (or worse) than any other… But, at least, it works on all bands and modes ! ? 73, Jacques, VE2JFE in Montreal ? Jacques ?and the gang Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp? don
|
Re: SX-110 2nd IF Circuit Design
Jacques; Holy Moly! as we used to say, no wonder we? are in no-mans’ land. Continuing the SX-42 diversion…I saw some of the detailed changes sheets on the BAMA site ?too, and they seem to address much of this. It seems clear that at some point there were significant changes beginning at the secondary of the 3rd IF transformer and ongoing, and the major rev must be adding that switch so that both the AM and FM go thru the first 7H7, whatever it is really doing. Wonder why the change/changes?? Makes one think the original circuit did not have enough amplification on AM. ?? I am still trying to make sense of the circuit; is ?the 7H7 really amplifying or what? Getting back to Sterves Original question about why one tube, not the other: One wonders Why use a Loctal when most are octals? The S-47 uses a 6SG7 in the same spot? but is called ??“FM 3RD IF AMP –AM DET” and it is produced at the same time. How is your band switch doing? Don VA3DRL ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Jacques_VE2JFE
Sent: Monday, October 31, 2022 12:21 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
Importance: High? Hi Don, ? The different produced versions of the SX-42 made me scratch my head big time… Let’s say that in the first versions (according to the schematic 89D210) the first 7H7 is identified as a “1st 濒颈尘颈迟别谤”. Probably because it is used only for the 10.7 MHz IF signal and then feeds the 2nd 7H7 tube identified as the “2nd limiter and 10.7 MHz AM detector”. The 455 kHz signal from the 3rd IF transformer is not coupled to the 1st 7H7 but applied to half of a 6H6 used as a detector, the other half of the same tube supporting the Noise Limiter function. ? In the late production versions (according to the 89D257 schematic) both the 455 kHz and 10.7 MHz signals are applied to the first 7H7 tube grid, and it’s designation was changed to “3rd 滨贵”. Both 455 kHz and 10.7 MHz AM signals are then “detected” by the second 7H7 tube (control grid to cathode) and the right part of the 6H6, used as a detector in the first versions, is completely disconnected. ? And A LOT of components values and circuitry topology changed between the first and the last SX-42 made. The one I restored last spring was something of a mix between the first and the last versions already (stamped May 12, 1947) and was more or less conform to the XXXX production run, so I decided to rebuild it to be compliant to the schematic 89D257E. ? Let’s figure here that there was 20 engineering changes applied successively to the production runs X, XX, XXX, XXXX and 1, updating the related schematics from 89D210 to 89D210K. Then the 89D257 come, with more engineering changes creating versions from A to G. The 89D257F required a change to the SW 1 (the Band switch), sections K and KK, and this is why I had not been able to implement this one. But the Rev. G change, which added a 6.8 ohms resistor (R108) in series with the 6H6 noise limiter heater was doable. ? At the end, I do not know if my own “version” of the SX-42 work better (or worse) than any other… But, at least, it works on all bands and modes ! ? 73, Jacques, VE2JFE in Montreal ? Jacques ?and the gang Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp? don
|
Re: SX-71 RF sensitivity knob
Yes, you understand correctly i guess the pot was replaced, and works as you describe. The tone pot was also replaced with the switch type, and it switches in an aftermarket calibrator. I am not sure if the RF pot switch is in use, I'm sure I looked during
the recap, but I don't remember .
toggle quoted message
Show quoted text
The RF gain pot on the SX-71 has no "click", unlike the volume control/a.c. power switch. On the SX-71 and other receivers, the S-meter works properly only when AGC is on and the RF gain control is at
maximum.? The meter reading will, indeed, rise and become inaccurate, as the RF gain is lowered.? Hope I understand your condition...
Jeep K3HVG
On 10/30/2022 3:41 PM Scott Petersen <s-petersen@...> wrote:
Hi, I am wondering if my RF sensitivity control is working correctly, possibly it may have been modified?
When you turn the gain down from the click, the signal seems to be muted from the bottom, as though it is a squelch, while the signal meter will rise to full scale as the gain is lowered. when the control is advanced it mutes the output completely at some pont.
Most radios that I have used the RF sensitivity works similar to a volume control, with the signal meter lowering as the gain is lowered, and the signal and noise level is lowered to the point of not receiving a signal.
Thanks,
Scott
|
Re: SX-71 RF sensitivity knob
The RF gain pot on the SX-71 has no "click", unlike the volume control/a.c. power switch. On the SX-71 and other receivers, the S-meter works properly only when AGC is on and the RF gain control is at maximum.? The meter reading will, indeed, rise and become inaccurate, as the RF gain is lowered.? Hope I understand your condition...
Jeep K3HVG
On 10/30/2022 3:41 PM Scott Petersen <s-petersen@...> wrote:
Hi, I am wondering if my RF sensitivity control is working correctly, possibly it may have been modified?
When you turn the gain down from the click, the signal seems to be muted from the bottom, as though it is a squelch, while the signal meter will rise to full scale as the gain is lowered. when the control is advanced it mutes the output completely at some pont.
Most radios that I have used the RF sensitivity works similar to a volume control, with the signal meter lowering as the gain is lowered, and the signal and noise level is lowered to the point of not receiving a signal.
Thanks,
Scott
|
Re: SX-110 2nd IF Circuit Design
Hi Don, ? The different produced versions of the SX-42 made me scratch my head big time… Let’s say that in the first versions (according to the schematic 89D210) the first 7H7 is identified as a “1st 濒颈尘颈迟别谤”. Probably because it is used only for the 10.7 MHz IF signal and then feeds the 2nd 7H7 tube identified as the “2nd limiter and 10.7 MHz AM detector”. The 455 kHz signal from the 3rd IF transformer is not coupled to the 1st 7H7 but applied to half of a 6H6 used as a detector, the other half of the same tube supporting the Noise Limiter function. ? In the late production versions (according to the 89D257 schematic) both the 455 kHz and 10.7 MHz signals are applied to the first 7H7 tube grid, and it’s designation was changed to “3rd 滨贵”. Both 455 kHz and 10.7 MHz AM signals are then “detected” by the second 7H7 tube (control grid to cathode) and the right part of the 6H6, used as a detector in the first versions, is completely disconnected. ? And A LOT of components values and circuitry topology changed between the first and the last SX-42 made. The one I restored last spring was something of a mix between the first and the last versions already (stamped May 12, 1947) and was more or less conform to the XXXX production run, so I decided to rebuild it to be compliant to the schematic 89D257E. ? Let’s figure here that there was 20 engineering changes applied successively to the production runs X, XX, XXX, XXXX and 1, updating the related schematics from 89D210 to 89D210K. Then the 89D257 come, with more engineering changes creating versions from A to G. The 89D257F required a change to the SW 1 (the Band switch), sections K and KK, and this is why I had not been able to implement this one. But the Rev. G change, which added a 6.8 ohms resistor (R108) in series with the 6H6 noise limiter heater was doable. ? At the end, I do not know if my own “version” of the SX-42 work better (or worse) than any other… But, at least, it works on all bands and modes ! ? 73, Jacques, VE2JFE in Montreal ? Jacques ?and the gang Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp? don
|
Re: SX-110 2nd IF Circuit Design
I have a suspicion that Hallicrafters, seeking their necessary profits, sought to design the best receivers they could using the most economical parts available to them, which may have varied from time to time.? Sales, marketing, and supply chain may have driven engineering, except on certain high-end models which may have been the personal pets of the engineers. ? 73 – Steve, KW4H ? Made me wonder too.? The 7H7 is a remote cut off tube similar to the 6SG7.? One would expect a sharp cut off tube as an FM limiter.? And how is it used as the AM detector? I am stuck with the galaxy phone as my computer.? It's hard to see schematics on it.? Hallicrafters used some odd tubes.?
toggle quoted message
Show quoted text
-------- Original message --------From: don Root <drootofallevil@...> Date: 10/30/22 7:28 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design Jacques ?and the gang Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp? don ? ? Hi all, ? There is no 6SC7 in the SX-42. The tubes used are (from the 89D257 latest schematic). ? 1st RF and 2nd RF: 6AG5 Local Oscillator & Mixer: 7F8 1st IF: 6SK7 2nd IF: 6SG7 3rd IF: 7H7 Limiter & AM detector: 7H7 Noise Limiter: 6H6 FM Discriminator: 6H6 BFO and S meter Amp: 7A4 Audio Inverter (phase splitter + driver): 6SL7 Audio Output: 2 x 6V6 ? 73, Jacques, VE2JFE in Montreal ? Scott, and ?Steve and the gang: I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 . he listed?? “SX-42 (1947-50) 6SK7, 6SG7”? ?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7 I also said “Wonder if we have the same printing…” ? Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42 ? For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7? I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books? Don VA3DRL
|
Re: SX-110 2nd IF Circuit Design
Made me wonder too.? The 7H7 is a remote cut off tube similar to the 6SG7.? One would expect a sharp cut off tube as an FM limiter.? And how is it used as the AM detector? I am stuck with the galaxy phone as my computer.? It's hard to see schematics on it.? Hallicrafters used some odd tubes.?
toggle quoted message
Show quoted text
-------- Original message -------- From: don Root <drootofallevil@...> Date: 10/30/22 7:28 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
Jacques ?and the gang Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp? don ? ? Hi all, ? There is no 6SC7 in the SX-42. The tubes used are (from the 89D257 latest schematic). ? 1st RF and 2nd RF: 6AG5 Local Oscillator & Mixer: 7F8 1st IF: 6SK7 2nd IF: 6SG7 3rd IF: 7H7 Limiter & AM detector: 7H7 Noise Limiter: 6H6 FM Discriminator: 6H6 BFO and S meter Amp: 7A4 Audio Inverter (phase splitter + driver): 6SL7 Audio Output: 2 x 6V6 ? 73, Jacques, VE2JFE in Montreal ? Scott, and ?Steve and the gang: I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 . he listed?? “SX-42 (1947-50) 6SK7, 6SG7”? ?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7 I also said “Wonder if we have the same printing…” ? Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42 ? For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7? I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books? Don VA3DRL
|
Re: SX-110 2nd IF Circuit Design
Jacques ?and the gang Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp? don ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Jacques_VE2JFE
Sent: Sunday, October 30, 2022 4:55 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? Hi all, ? There is no 6SC7 in the SX-42. The tubes used are (from the 89D257 latest schematic). ? 1st RF and 2nd RF: 6AG5 Local Oscillator & Mixer: 7F8 1st IF: 6SK7 2nd IF: 6SG7 3rd IF: 7H7 Limiter & AM detector: 7H7 Noise Limiter: 6H6 FM Discriminator: 6H6 BFO and S meter Amp: 7A4 Audio Inverter (phase splitter + driver): 6SL7 Audio Output: 2 x 6V6 ? 73, Jacques, VE2JFE in Montreal ? Scott, and ?Steve and the gang: I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 . he listed?? “SX-42 (1947-50) 6SK7, 6SG7”? ?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7 I also said “Wonder if we have the same printing…” ? Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42 ? For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7? I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books? Don VA3DRL
|
Greetings to the Group:
I have given up on the original Hallicrafters PS-500 design.?? If you look at the various documentation, the SR-400 Cyclone (the radio that it is supposed to power) specifies a low B+ of 270 volts.?? The power supply documentation specifies 280 volts at 100 mA.?? Yet, if you look at the SR-400 schematic carefully, you will find that the minimum possible current drain for the unit on receive is about 140 mA due to fixed loads such as the 0A2 regulator circuit and the PA screen bleeder resistors.?? The actual measured load on receive is 183 mA.??
I found no combination of chokes and filter capacitors that would prevent the receive voltage from exceeding 280 volts and still allow the voltage to be reasonable in transmit; the voltage swing was well over 20 volts.?? In order to keep some of the voltage sensitive circuits like the heterodyne oscillator circuit working as well as possible in transmit, I found it necessary to more or less completely re-design the power supply.?? The low B+ in my PS-500 is now regulated.
Please find the as-built schematic attached.
--
Jim T.
KB6GM
|
Re: SX-110 2nd IF Circuit Design
Hi all, ? There is no 6SC7 in the SX-42. The tubes used are (from the 89D257 latest schematic). ? 1st RF and 2nd RF: 6AG5 Local Oscillator & Mixer: 7F8 1st IF: 6SK7 2nd IF: 6SG7 3rd IF: 7H7 Limiter & AM detector: 7H7 Noise Limiter: 6H6 FM Discriminator: 6H6 BFO and S meter Amp: 7A4 Audio Inverter (phase splitter + driver): 6SL7 Audio Output: 2 x 6V6 ? 73, Jacques, VE2JFE in Montreal ? Scott, and ?Steve and the gang: I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 . he listed?? “SX-42 (1947-50) 6SK7, 6SG7”? ?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7 I also said “Wonder if we have the same printing…” ? Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42 ? For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7? I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books? Don VA3DRL
|
Re: SX-110 2nd IF Circuit Design
Depend on WHICH diagram… I.E. which production version of the SX-42… ? 73, Jacques, VE2JFE in Montreal ? The SX-42 schematic shows a 7H7 as the third IF, printed on the diagram. 73 – Steve, KW4H
|
Re: SX-110 2nd IF Circuit Design
The SX-42 schematic shows a 7H7 as the third IF, printed on the diagram. ? 73 – Steve, KW4H ? Hello n7qmm25 and others YES; Depending on font etc and goobers in printing C and G look quite similar Let’s just say the C ?that I see in Dachis was a poor print of a G ?or my eyes are really tired so the second tube is REALLY a? 6SG7. that agrees with most and just now I am reading ??James’s …sx-42 repair ?which lists?? ….edited
6SK7 - 1st IF
6SG7 - 2nd IF
6H6 - 2nd detector / Noise Limiter
7H7 (two) - FM Limiters? ……… Now ?I just looked at the BAMA schematic ?again and see that the 7H7’s are called “Limiters” [for the FM] and don’t see any sign of a “3rd IF” …But … Dachis ?says ?????“7H7 3rd IF Amp “
Osterman ?says ?“7H7 IF Amp “ … Beginning not to believe the gurus. Don VA3DRL?
toggle quoted message
Show quoted text
|
Re: SX-110 2nd IF Circuit Design
Hello n7qmm25 and others YES; Depending on font etc and goobers in printing C and G look quite similar Let’s just say the C ?that I see in Dachis was a poor print of a G ?or my eyes are really tired so the second tube is REALLY a? 6SG7. that agrees with most and just now I am reading ??James’s …sx-42 repair ?which lists?? ….edited
6SK7 - 1st IF
6SG7 - 2nd IF
6H6 - 2nd detector / Noise Limiter
7H7 (two) - FM Limiters? ……… Now ?I just looked at the BAMA schematic ?again and see that the 7H7’s are called “Limiters” [for the FM] and don’t see any sign of a “3rd IF” …But … Dachis ?says ?????“7H7 3rd IF Amp “
Osterman ?says ?“7H7 IF Amp “ … Beginning not to believe the gurus. Don VA3DRL? =======trimd
|
Re: SX-110 2nd IF Circuit Design
My 62 has 7H7 , and the 62a has 6SG7 in it's place
On Oct 30, 2022 4:40 PM, n7qmm25 <n7qmm25@...> wrote:
toggle quoted message
Show quoted text
My SX 42 has 6SK7, 6SG7 and 7H7. Clearly stamped into the metal chassis. Do you supposed one had tired eyes and thought he saw a C instead of a G?
On 10/30/2022 12:48 PM, don Root wrote:
?
Scott, and ?Steve and the gang:
I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 .
he listed?? “SX-42 (1947-50) 6SK7, 6SG7”?
?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7
I also said “Wonder if we have the same printing…”
?
Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42
?
For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7?
I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books?
Don VA3DRL
=======trimd
|
Re: SX-110 2nd IF Circuit Design
It was tired eyes and a transcription error.? The 7H7 is the third IF. ? 73, ? Steve, KW4H ? My SX 42 has 6SK7, 6SG7 and 7H7. Clearly stamped into the metal chassis. Do you supposed one had tired eyes and thought he saw a C instead of a G?
toggle quoted message
Show quoted text
On 10/30/2022 12:48 PM, don Root wrote: ? Scott, and ?Steve and the gang: I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 . he listed?? “SX-42 (1947-50) 6SK7, 6SG7”? ?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7 I also said “Wonder if we have the same printing…” ? Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42 ? For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7? I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books? Don VA3DRL =======trimd
|
Re: SX-110 2nd IF Circuit Design
My SX 42 has 6SK7, 6SG7 and 7H7. Clearly stamped into the metal
chassis. Do you supposed one had tired eyes and thought he saw a C
instead of a G?
On 10/30/2022 12:48 PM, don Root wrote:
toggle quoted message
Show quoted text
?
Scott,
and ?Steve and the gang:
I think
Steve clarified a mistake re the sx-110 , but he listed IF
tubes for others ?and never said anything about my comment
on the sx-42 .
he listed??
“SX-42 (1947-50) 6SK7, 6SG7”?
?my? ?1996
Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7
I also said
“Wonder if we have the same printing…”
?
Now I wonder
if ? my? ?1996 Dachis ?book and my ?Osterman[ second
edition]? books ?are wrong ??about the 42
?
For the 62
you mentioned ?,Osterman ?lists the same IF tubes as it
lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A
version seems to be the same except for the speaker
impedance,, BUT Dachis says? 6SK7?6SG7?6SG7?
I guess I
must be off-track, and/or cant read these details so maybe
somebody else can check these books?
Don VA3DRL
=======trimd
|
Re: SX-110 2nd IF Circuit Design
Don, ? I just checked, and yes – there’s a third IF tube for the SX-42 – the 7H7.? I overlooked that.? FYI, my Osterman book is the fourth edition. ? 73 – Steve, KW4H ? ? Scott, and ?Steve and the gang: I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 . he listed?? “SX-42 (1947-50) 6SK7, 6SG7”? ?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7 I also said “Wonder if we have the same printing…” ? Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42 ? For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7? I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books? Don VA3DRL =======trimd
|
Re: SX-110 2nd IF Circuit Design
? Scott, and ?Steve and the gang: I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 . he listed?? “SX-42 (1947-50) 6SK7, 6SG7”? ?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7 I also said “Wonder if we have the same printing…” ? Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42 ? For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7? I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books? Don VA3DRL =======trimd
|
SX-71 RF sensitivity knob
Hi, I am wondering if my RF sensitivity control is working correctly, possibly it may have been modified?
When you turn the gain down from the click, the signal seems to be muted from the bottom, as though it is a squelch, while the signal meter will rise to full scale as the gain is lowered. when the control is advanced it mutes the output completely at some pont.
Most radios that I have used the RF sensitivity works similar to a volume control, with the signal meter lowering as the gain is lowered, and the signal and noise level is lowered to the point of not receiving a signal.
Thanks,
Scott
toggle quoted message
Show quoted text
A recent posting got me to looking through my archives. I found the following short discussion that may be of interest to some.
In this discussion we will be looking at the high voltage bleeder resistors and the metering ckt resistor. Also, the discussion is related to the following; P-500, PS-500-120, PS-500-AC, PS-500A-AC and the PS-150-120.?
?
First the metering resistor. The metering resistor in the 150 series and the 500 series power supplies is R207. In all the power supplies except the PS-500A-AC it is documented as a 10ohm 1watt resistor. In the PS-500A-AC is documented
as a 10ohm 5watt resistor.?
With the 1-watt resistor in place, during tune-up or if you experience an antenna problem, you can easily see in excess of .450ma of plate current. That is over 2 watts dumped into R207. When that resistor opens you lose transmitter
power and get a rather strange indication. When you turn the unit on with that resistor open, while in receive mode, you will get slowly increasing plate current indication on a meter plugged into the metering jacks on the power supply.?
When the power supply for the 400A was produced, that resistor was changed to a 5-watt resistor. My personal choice is the square, ceramic, 10-watt 10-ohm resistor?
?
Now for the high voltage bleeder resistors. This issue is complicated by the variations in the Hallicrafters documentation. Some documentation for the 500 series supplies calls out 15k 10watt resistors. Some documentation calls
out 20k 10watt resistors. ?
Over the years I have repaired hundreds of the 150 and 500 power supplies. In power supplies with the 15k 10watt resistors, with a lot of hours of service, you will find three common degradations. First the insulation on the red
wires from the resistors to the capacitors will be melted and blackened at the resistor end. You will also find the platting on the resistor leads flaky and pealing. Then you will notice the solder connection on the terminal strips have crystalized and coated
with lead oxide. In some cases, continuity is lost.?
In the factory units that were produced with the 20k 10watt resistors you do not find the degradations. I personally stocked 20k 20watt replacements?
?Walt Cates,
WD0GOF
?
Your past has no control over your future. Only your NOW can impact your future.
|
don Root
Jacques_VE2JFE