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S-40 Restoration - Oddity around V2
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Glad to have found this group!
I've got an S-40 on the bench -- a restoration project for a friend. ?The receiver belonged to his grandfather (who was licensed), then was passed on to him. ?For the most part, the receiver appears to be all factory, which is always helpful. ?However, his grandfather had been into the radio, and I've found a circuit alteration on V-2 that I'm uncertain about. ?This is a 2nd revision model of the S-40, by the way. ? The attached schematic shows V-2 and the area around it as originally designed by Hallicrafters. ?Have a look at pin 5 (grid #1) -- the alteration I'm seeing is off of there. ?Here are the changes: - R30 (10 ohms) is eliminated - C16 connects directly from pin 5 to S/IF - C26 connects directly from pin 5 to ground So, the modification puts three connections on pin 5 -- R7 to ground, C26 to ground, and C16 to S/IF. Before deciding whether to revert this back to factory, I'm curious as to why this might have been done. ?I've searched online and can't find this modification anywhere. ? 73 - Steve, KW4H |
开云体育Steve...
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It looks like elimination of R30 would increase the Local Oscillator
injection level.? I’m not sure why this would be a good idea?
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73,
ART
W6REQ
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? From: Steven Reed via groups.io
Sent: Sunday, September 18, 2022 6:32 AM
Subject: [HallicraftersRadios] S-40 Restoration - Oddity around
V2 ?
Glad
to have found this group! I've got an S-40 on the bench -- a restoration project for a friend.? The receiver belonged to his grandfather (who was licensed), then was passed on to him.? For the most part, the receiver appears to be all factory, which is always helpful.? However, his grandfather had been into the radio, and I've found a circuit alteration on V-2 that I'm uncertain about.? This is a 2nd revision model of the S-40, by the way.? The attached schematic shows V-2 and the area around it as originally designed by Hallicrafters.? Have a look at pin 5 (grid #1) -- the alteration I'm seeing is off of there.? Here are the changes: - R30 (10 ohms) is eliminated - C16 connects directly from pin 5 to S/IF - C26 connects directly from pin 5 to ground So, the modification puts three connections on pin 5 -- R7 to ground, C26 to ground, and C16 to S/IF. Before deciding whether to revert this back to factory, I'm curious as to why this might have been done.? I've searched online and can't find this modification anywhere.? 73 - Steve, KW4H |
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Thanks for the reply, Art.? Many old receivers never did very well on the upper bands -- possibly, it was an experiment to see if fiddling with the oscillator circuit would help.? Unless any other information arises, think I'll just restore it to factory.? I'm used to seeing a lot of modifications and (failed) experiments, but this one is quite a puzzle.??
73 - Steve, KW4H |
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Phil Patton
R30 is almost certainly a grid stopper to suppress spurious oscillations. Unless V2 grid pulls a ton of current (I would expect it to be zero) 10 ohms will have no effect on the signal level. As with many things considered "good engineering practice" eliminating it probably does absolutely?nothing! On Sun, Sep 18, 2022, 2:52 PM Steven Reed via <reedsteve=[email protected]> wrote: Thanks for the reply, Art.? Many old receivers never did very well on the upper bands -- possibly, it was an experiment to see if fiddling with the oscillator circuit would help.? Unless any other information arises, think I'll just restore it to factory.? I'm used to seeing a lot of modifications and (failed) experiments, but this one is quite a puzzle.?? |
开云体育Phil...
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Thanks for the comment!? I wondered about to low value of 10
ohms.
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73,
ART
W6REQ
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? From: Phil
Patton
Sent: Sunday, September 18, 2022 3:23 PM
Subject: Re: [HallicraftersRadios] S-40 Restoration - Oddity around
V2 ?
R30 is almost certainly a grid stopper to suppress spurious oscillations.
Unless V2 grid pulls a ton of current (I would expect it to be zero) 10 ohms
will have no effect on the signal level. As with many things considered "good
engineering practice" eliminating it probably does absolutely nothing!
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On Sun, Sep 18, 2022, 2:52 PM Steven Reed via
<reedsteve@...> wrote:
Thanks for the reply, Art.? Many old receivers never did very well on the upper bands -- possibly, it was an experiment to see if fiddling with the oscillator circuit would help.? Unless any other information arises, think I'll just restore it to factory.? I'm used to seeing a lot of modifications and (failed) experiments, but this one is quite a puzzle.? |
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I found a much more detailed manual for the S-40 and, as it turns out, it has a highly detailed description of most every component.? Very well-written.? Anyway, my question was answered by Phil Patton (thanks!) but I'll share Hallicrafter's info here.? The purpose of R-30 is to suppress parasitic oscillations.? C-16 is the oscillator grid coupling capacitor (obviously), and C-26 is an additional fixed trimmer across the resonant circuit.? Eliminating R-30 is unhelpful, and wiring C-26 directly to the grid of the oscillator is almost certainly an electrical mistake, as it exists as a trimmer for the oscillator circuit, which exists on the other side of C-16.? No question this needs to go back to the factory design -- and I'll have to keep a very close eye out for other little experiments that might exist in this specimen.??
73 - Steve, KW4H |
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Many decades ago I restored an S40. It was my first receiver. My dad bought it used at Fortune Electronics in San Carlos CA for $20. New caps, many out of spec resistors replaced, weak tubes replaced and a full alignment. After all that work, performance at the upper end of its frequency range was still very poor, drifty and deaf. A cheap CB walkie talkie could hear many stations that the restored S40 could not. It’s a nice looking radio but don’t expect too much.? Mark AF6IM? On Sun, Sep 18, 2022 at 12:52 PM Steven Reed via <reedsteve=[email protected]> wrote: Thanks for the reply, Art.? Many old receivers never did very well on the upper bands -- possibly, it was an experiment to see if fiddling with the oscillator circuit would help.? Unless any other information arises, think I'll just restore it to factory.? I'm used to seeing a lot of modifications and (failed) experiments, but this one is quite a puzzle.?? --
AF6IM www.parachutemobile.com |
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Mark,
Yeah, a lot of these older sets can be deaf as a doornail on the higher frequencies.? I won't be keeping the S-40 -- it belongs to a good friend who is disabled, and it's a restoration for nostalgic purposes.? His grandfather owned the radio when it was new, then it was passed on to his father, and then to him.?? 73 - Steve, KW4H |
开云体育I think one problem is rhat Hallicrafters and others pushed the upper limits of their receivers for promotional purposes.? Using higher Gm tubes in the later models helped but I think the rf coils were not up to it.? Compare rhe performance of an S-40 to an RCA AR 88,? the AR 88 has low loss coils and very good performance to 30 Mhz.? It also cost about ten times as much.? -------- Original message -------- From: MarkJ <BOEING377@...> Date: 9/19/22 10:19 AM (GMT-08:00) Subject: Re: [HallicraftersRadios] S-40 Restoration - Oddity around V2 Many decades ago I restored an S40. It was my first receiver. My dad bought it used at Fortune Electronics in San Carlos CA for $20. New caps, many out of spec resistors replaced, weak tubes replaced and a full alignment. After all that work, performance at the upper end of its frequency range was still very poor, drifty and deaf. A cheap CB walkie talkie could hear many stations that the restored S40 could not. It’s a nice looking radio but don’t expect too much.? Mark AF6IM? On Sun, Sep 18, 2022 at 12:52 PM Steven Reed via <reedsteve=[email protected]> wrote: Thanks for the reply, Art.? Many old receivers never did very well on the upper bands -- possibly, it was an experiment to see if fiddling with the oscillator circuit would help.? Unless any other information arises, think I'll just restore it to factory.? I'm used to seeing a lot of modifications and (failed) experiments, but this one is quite a puzzle.?? -- AF6IM www.parachutemobile.com |
开云体育Whether it’s Hallicrafters, Hammarlund, National, or almost any of the other brands back in the day, people did indeed get what they paid for.? And even some of the “relatively” higher-end receivers (e.g., Hammarlund HQ-180A) were still at least partially deaf on the higher bands.? As you so aptly pointed out, a lot of it had to do with sales and marketing.? One of the most sensitive receivers ever to cross my bench was a National HRO-60 – the plug-in coils went a long way towards sensitivity on the higher bands – but the cost to the purchaser was bananas – about $500 in 1952 dollars.? That’s about $5,500 today.? ? 73 – Steve, KW4H ? From: <[email protected]> on behalf of Richard Knoppow <1oldlens1@...> ? I think one problem is rhat Hallicrafters and others pushed the upper limits of their receivers for promotional purposes.? Using higher Gm tubes in the later models helped but I think the rf coils were not up to it.? Compare rhe performance of an S-40 to an RCA AR 88,? the AR 88 has low loss coils and very good performance to 30 Mhz.? It also cost about ten times as much.? ? ? ? ? ? |
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In 1959, my novice receiver, an S-40B, did yoeman service on 80, 40, and 15 meters.? I worked many stations on 15, to include a few DX stations.? Not having any reference to compare with at the time, it seemed ok to me.? Got the QSLs to prove it.? In 1960, it was replaced by a brand new SX-99. And so began the trek to now.....? As we speak, there is an S-40B and an SX-99 still in the radio collection area.
Jeep K3HVG
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开云体育I use my S-40B mostly on 40 and 80 CW, paired with an Elmac AF-67. I also have an R-388, a BC-342, and an NC-183, all of which are "better" than the S-40B, but the S-40B is much more portable for setting up elsewhere and it brings back memories of my Novice days in the 50s when I couldn't have afforded any of the others so I have a lot of fun with it sorting out signals with my ears. ? The S-40B schematic is lacking R-30 as shown in your schematic for the S-40. The connection is from the oscillator coilset through C16 to pin 5 of V2 with R7 (18 k) from pin 5 to ground. ? 73, ? Maynard W6PAP ? ? On Monday, September 19, 2022 07:09:03 PM KW4H via groups.io wrote:
> Whether it’s Hallicrafters, Hammarlund, National, or almost any of the other > brands back in the day, people did indeed get what they paid for. And even > some of the “relatively” higher-end receivers (e.g., Hammarlund HQ-180A) > were still at least partially deaf on the higher bands. As you so aptly > pointed out, a lot of it had to do with sales and marketing. One of the > most sensitive receivers ever to cross my bench was a National HRO-60 – the > plug-in coils went a long way towards sensitivity on the higher bands – but > the cost to the purchaser was bananas – about $500 in 1952 dollars. That’s > about $5,500 today. > > 73 – Steve, KW4H > > From: <[email protected]> on behalf of Richard Knoppow > <1oldlens1@...> Reply-To: <[email protected]> > Date: Monday, September 19, 2022 at 11:50 AM > To: <[email protected]> > Subject: Re: [HallicraftersRadios] S-40 Restoration - Oddity around V2 > > I think one problem is rhat Hallicrafters and others pushed the upper limits > of their receivers for promotional purposes. Using higher Gm tubes in the > later models helped but I think the rf coils were not up to it. Compare rhe > performance of an S-40 to an RCA AR 88, the AR 88 has low loss coils and > very good performance to 30 Mhz. It also cost about ten times as much. > > > > ? |
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Steve, I would try leaving the mod. Floating 10 ohms from ground is not much different from 0 ohms, and direct coupling of caps is not much of a change. It may add a little sensitivity but may introduce a little bit of “squeaky”. Try it.
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Albert Hallicrafters Rehabs KR3HAB On Sunday, September 18, 2022, 9:20 PM, Steven Reed via groups.io <reedsteve@...> wrote:
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After reading Steve’s comment I agree whole heartedly. I am in India and going off memory which isnt too great,
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Albert KR3HAB On Monday, September 19, 2022, 10:48 PM, KW4H via groups.io <reedsteve@...> wrote:
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开云体育? A comment that the S 40 A has differences from the S 40 and the S 40 B is extensively redesigned.? I think the S 40 B is superior to the earlier models even though many of the changes appear to make it cheaper to make.? ?I also have an S 20 R which is very close electrically to the early S 40.? Since my S 20 R had been somewhat modified an whoever rebuilt it had left out the noise limiter, I modified it to the S 40 A circuit including the detector. Since the S 40 A has a 6SG7 RF in place of the 6SK7 in the S 20 R it has noticeably better performance above about 15 Mhz.? I think it has different RF couls also with higher Q and lower loss.? Hallicrafters restyled several of their pre war receivers after the war but later redesigned them with better circuits and better components.? Keep in mind that following the war price and wage controlls came off so there was.substantial inflation. You can see this in the advertising of the time.? The price targets set for various products went out of line very fast.? I think it surprised a lot of people. -------- Original message -------- From: "Albert Garrou via groups.io" <albertandjune@...> Date: 9/19/22 7:53 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] S-40 Restoration - Oddity around V2 Albert KR3HAB
On Monday, September 19, 2022, 10:48 PM, KW4H via groups.io <reedsteve@...> wrote:
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