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S-38 recapping Query

W4LSV Barry All Messages By This Member #31504 I am in the process of recapping a S-38 that was given to me. ? I have not powered it up. ?It still has all the paper capacitors and non polarized AC Plug. ?It has 6 tubes and a BFO. ? It does not have the C-38 and C-39 silver micas that, according to my schematic, were added to later models of S-38. ? I have found an extra 0.2 @200 V paper capacitor connected between Pin 6 of 12SK7 tube and ground. ?Its condition is similar to all the other paper capacitors that I am replacing. ?As far as the physical location, one lead is connected to the same ground lug that C-36 uses. ? Should I replace it or not? I would greatly appreciate any insights and suggestions, as my experience with vintage radios is minimal? ? 73, Barry W4LSV
Richard Knoppow All Messages By This Member #31507 I am looking at a schematic from Riders, probably from BAMA. It shows Pin 6 of the 12SK7 to be the screen grid, going to a line also connected to the a 0.25mfd cap on the B+ going to T-4 and the screen of the 35L6 output tube. There is a 0.25 mfd cap connected to ground to by-pass this line but in this schematic its shown at the B+ side of T-4. Same line. Its called C-17. This line goes to the B+ filter. Its bypassed by one of the filter caps but that may not be effective at RF so this additional cap is included. See if there is also a bypass at the B+ input to T-4. It may have been moved or there may have been caps in both locations if it was found better bypassing was needed. There were evidently lots of changes to the S-38. From the circuit I would keep a cap there, replacing it with a new cap of course. Even though the B+ goes to a filter cap there may be pick up in the wiring or the filter cap may not give good bypassing at RF. toggle quoted message Show quoted text On 1/11/2025 6:08 AM, W4LSV Barry via groups.io wrote: I am in the process of recapping a S-38 that was given to me. ? I have not powered it up. ?It still has all the paper capacitors and non polarized AC Plug. ?It has 6 tubes and a BFO. ? It does not have the C-38 and C-39 silver micas that, according to my schematic, were added to later models of S-38. I have found an extra 0.2 @200 V paper capacitor connected between Pin 6 of 12SK7 tube and ground. ?Its condition is similar to all the other paper capacitors that I am replacing. ?As far as the physical location, one lead is connected to the same ground lug that C-36 uses. Should I replace it or not? I would greatly appreciate any insights and suggestions, as my experience with vintage radios is minimal 73, Barry W4LSV -- Richard Knoppow Los Angeles WB6KBL SKCC 19998
don Root All Messages By This Member #31514 Edited 开云体育 Barry , you have not seen many replies so I will give it a shot, and I forget what Richard said. ??Oh now I see.. I’m saying the same thing. Oh well, ??? Re? It does not have the C-38 and C-39 silver micas that, according to my schematic, were added to later models of S-38. Is “my schematic” one that came with the radio? or? ?some later schematic from ??? ??where do they[C-38 and C-39] go?? Re? ?I have found an extra 0.2 @200 V paper capacitor connected between Pin 6 of 12SK7 tube and ground. ?It might have helped stabilize the “almost B+”? voltages at pin 6 [screen] or maybe it is a replacement for the 0.25 . Recall this is a schematic not a wiring drawing, so it theoretically could go either place ? ? toggle quoted message Show quoted text From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow via groups.io Sent: Saturday, January 11, 2025 10:45 AM To: [email protected] Subject: Re: [HallicraftersRadios] S-38 recapping Query ? I am looking at a schematic from Riders, probably from BAMA. It shows Pin 6 of the 12SK7 to be the screen grid, going to a line also connected to the a 0.25mfd cap on the B+ going to T-4 and the screen of the 35L6 output tube. There is a 0.25 mfd cap connected to ground to by-pass this line but in this schematic its shown at the B+ side of T-4. Same line. Its called C-17. This line goes to the B+ filter. Its bypassed by one of the filter caps but that may not be effective at RF so this additional cap is included. See if there is also a bypass at the B+ input to T-4. It may have been moved or there may have been caps in both locations if it was found better bypassing was needed. There were evidently lots of changes to the S-38. From the circuit I would keep a cap there, replacing it with a new cap of course. Even though the B+ goes to a filter cap there may be pick up in the wiring or the filter cap may not give good bypassing at RF. On 1/11/2025 6:08 AM, W4LSV Barry via groups.io wrote: I am in the process of recapping a S-38 that was given to me. ? I have not powered it up. ?It still has all the paper capacitors and non polarized AC Plug. ?It has 6 tubes and a BFO. ? It does not have the C-38 and C-39 silver micas that, according to my schematic, were added to later models of S-38. I have found an extra 0.2 @200 V paper capacitor connected between Pin 6 of 12SK7 tube and ground. ?Its condition is similar to all the other paper capacitors that I am replacing. ?As far as the physical location, one lead is connected to the same ground lug that C-36 uses. Should I replace it or not? I would greatly appreciate any insights and suggestions, as my experience with vintage radios is minimal 73, Barry W4LSV -- Richard Knoppow Los Angeles WB6KBL SKCC 19998 ? -- don??? va3drl
W4LSV Barry All Messages By This Member #31515 Richard, thanks for the explanation and advice. ?I’ll replace the additional 0.2 capacitor. ? 73 Barry
W4LSV Barry All Messages By This Member #31516 Hi Don, Thank you for adding the drawing and explanation. ?Your comment about it might be a replacement for the 0.25. ?I found 2 additional Electrolytic Capacitors added in parallel with 2 of the leads from the Multi value tubular capacitor. ?Rather than cutting off the leads of the 2 bad sections, the new ones were just wired in parallel. So it’s possible that was also done in this instance. ?? I sure appreciate the help. ? When I ?was a Novice in 1965, a friend loaned me his Hallicrafters S-38 to use as the receiver in my station. ? Johnson Adventurer was my transmitter. I had to return the S-38. ? I’ve recapped my Johnson Adventurer and used it during Straight Key Night several times with my Novice J-38 Key. ? ?Thought it would be fun to try using this newly acquired S-38 during Straight Key Night next year. ? 73 Barry W4LSV
don Root All Messages By This Member #31517 开云体育 Barry, Re ?Your comment about it might be a replacement for the 0.25.? Is the .25 also in the circuit? ? Re additional Electrolytic Capacitors added in parallel with 2 of the leads from the Multi value tubular capacitor. ?Many people say not to leave the old electrolytics connected since they might short out. There are various ways of dealing with this, and yet keep the can there for appearances. My guess is that that 0.2 was found to be needed; but perhaps it was factory original on your version? It is too bad that the general “we” have not accumulated more manuals/schematics for various versions. ? toggle quoted message Show quoted text From: [email protected] [mailto:[email protected]] On Behalf Of W4LSV Barry via groups.io Sent: Sunday, January 12, 2025 9:36 AM To: [email protected] Subject: Re: [HallicraftersRadios] S-38 recapping Query ? Hi Don, Thank you for adding the drawing and explanation. ?Your comment about it might be a replacement for the 0.25. ?I found 2 additional Electrolytic Capacitors added in parallel with 2 of the leads from the Multi value tubular capacitor. ?Rather than cutting off the leads of the 2 bad sections, the new ones were just wired in parallel. So it’s possible that was also done in this instance. ?? I sure appreciate the help. ? When I ?was a Novice in 1965, a friend loaned me his Hallicrafters S-38 to use as the receiver in my station. ? Johnson Adventurer was my transmitter. I had to return the S-38. ? I’ve recapped my Johnson Adventurer and used it during Straight Key Night several times with my Novice J-38 Key. ? ?Thought it would be fun to try using this newly acquired S-38 during Straight Key Night next year. ? 73 Barry W4LSV _._,_._,_ -- don??? va3drl
Richard Knoppow All Messages By This Member #31518 Putting new caps in parallel with old ones serves no purpose, either for trouble shooting or repair. If the old cap is leaky the leakage is still there. Just replace it. To do otherwise is just laziness. Note, sometimes a small value paper or mica caps in parallel with an electrolytic will allow efficient bypassing of RF. The cap in the S-38 also shows up in the Echophone EC-1, which is its predecessor. Electrolytic caps often have very poor ESR at high frequencies allowing RF on the B+ line to couple between circuits. Both paper and mica caps have much better performance and both were used for the purpose. toggle quoted message Show quoted text On 1/12/2025 2:18 PM, don Root wrote: Barry, Re _Your comment about it might be a replacement for the 0.25_.? Is the .25 also in the circuit? Re _additional Electrolytic Capacitors added in parallel with 2 of the leads from the Multi value tubular capacitor_. ?Many people say not to leave the old electrolytics connected since they might short out. There are various ways of dealing with this, and yet keep the can there for appearances. My guess is that that 0.2 was found to be needed; but perhaps it was factory original on your version? It is too bad that the general “we” have not accumulated more manuals/ schematics for various versions. From:[email protected] [mailto:[email protected]] On Behalf Of W4LSV Barry via groups.io Sent: Sunday, January 12, 2025 9:36 AM To: [email protected] Subject: Re: [HallicraftersRadios] S-38 recapping Query Hi Don, Thank you for adding the drawing and explanation. ?Your comment about it might be a replacement for the 0.25. ?I found 2 additional Electrolytic Capacitors added in parallel with 2 of the leads from the Multi value tubular capacitor. ?Rather than cutting off the leads of the 2 bad sections, the new ones were just wired in parallel. So it’s possible that was also done in this instance. I sure appreciate the help. When I ?was a Novice in 1965, a friend loaned me his Hallicrafters S-38 to use as the receiver in my station. ? Johnson Adventurer was my transmitter. I had to return the S-38. ? I’ve recapped my Johnson Adventurer and used it during Straight Key Night several times with my Novice J-38 Key. ? ?Thought it would be fun to try using this newly acquired S-38 during Straight Key Night next year. 73 Barry W4LSV _._,_._,_ -- don??? va3drl -- Richard Knoppow Los Angeles WB6KBL SKCC 19998
W4LSV Barry All Messages By This Member #31547 Richard and Don, Thank you for the info and help with my project. ?? ? 73 Barry W4LSV
Bruce Collins Member Profile All Messages By This Member #31548 The small capacitor on the screen node of the 12SK87 is to insure there is no AC ripple or any RF on the screen.? There should only be DC here.?
Bruce Collins Member Profile All Messages By This Member #31549 Crap! ?12SK7….? toggle quoted message Show quoted text On Tue, Jan 21, 2025 at 11:31?AM Bruce Collins via <kb0tj1=[email protected]> wrote: The small capacitor on the screen node of the 12SK87 is to insure there is no AC ripple or any RF on the screen.? There should only be DC here.?
W4LSV Barry All Messages By This Member #31550 Bruce, Thanks for additional info. ?I will verify I only have DC there. ? ?

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