|
?While following Glen’s S-38e topic? which we hijacked for S-40’s discussions, I came upon the ?S-38B manual? on BAMA which shows and lists PL-2 plug in the AC line cord, and SO-1 on the back of the chassis The manual picture shows SO-1 on the chassis rear apron right side [rear view]. . I could not see these on other versions. Perhaps that was UL’s first punch at safety? So I wonder if there are really there on the B?? And is there ?nothing equivalent on C,D,E? or maybe the back cover carries the equivalent? disconnect, but is not shown in the schematics?.. or what ? ? -- don??? va3drl
|
My late, lamented, S-38B had a TV type power connector on the back.
The female part was riveted to the back cover so as to form an
interlock. One needed a TV type cheater cord to connect the receiver for
servicing. This connector is not polarized nor was the line plug at the
other end. For DC one tries the plug both ways since it won't work at
all if you get it in wrong. The idea of the interlocking plug is that
you can't power up the receiver if the back cover is removed and there
is nothing "hot" touchable when the cover is in place.
I am not sure how other versions of the S-38 are arranged. I do
have an S-38 original in the closet and could look. Too lazy to do it
right now.
toggle quoted message
Show quoted text
On 11/4/2024 2:38 PM, don Root wrote: ?While following Glen’s S-38e topic? which we hijacked for S-40’s
discussions, I came upon the ?S-38*B***manual? on BAMA which shows and
lists PL-2 plug in the AC line cord, and SO-1 on the back of the chassis
The manual picture shows SO-1 on the chassis rear apron right side [rear
view]. . I could not see these on other versions.
Perhaps that was UL’s first punch at safety? So I wonder if there are
really there on the B?
And is there ?nothing equivalent on C,D,E? or maybe the back cover
carries the equivalent? disconnect, but is not shown in the
schematics?.. or what ? **
--
don??? va3drl
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Well Richard, then maybe yours was an S-38B? mark 2? or run2 or whatever ? This below is snipped and edited from the BAMA version B that I downloaded some time back. ?
I know about what you are saying, my various versions are in deep storage, and I believe? I have seen those backs on the D , but why not in the manuals? ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Monday, November 4, 2024 6:15 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-38B, variations? My late, lamented, S-38B had a TV type power connector on the back.
The female part was riveted to the back cover so as to form an
interlock. One needed a TV type cheater cord to connect the receiver for
servicing. This connector is not polarized nor was the line plug at the
other end. For DC one tries the plug both ways since it won't work at
all if you get it in wrong. The idea of the interlocking plug is that
you can't power up the receiver if the back cover is removed and there
is nothing "hot" touchable when the cover is in place.
I am not sure how other versions of the S-38 are arranged. I do
have an S-38 original in the closet and could look. Too lazy to do it
right now.
On 11/4/2024 2:38 PM, don Root wrote: ?While following Glen’s S-38e topic? which we hijacked for S-40’s
discussions, I came upon the ?S-38*B***manual? on BAMA which shows and
lists PL-2 plug in the AC line cord, and SO-1 on the back of the chassis
The manual picture shows SO-1 on the chassis rear apron right side [rear
view]. . I could not see these on other versions.
Perhaps that was UL’s first punch at safety? So I wonder if there are
really there on the B?
And is there ?nothing equivalent on C,D,E? or maybe the back cover
carries the equivalent? disconnect, but is not shown in the
schematics?.. or what ? **
--
don??? va3drl
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
-- don??? va3drl
|
This appears to be a photo with the back removed, note the tubes
visible. The mating connector is riveted to the back cover.
toggle quoted message
Show quoted text
On 11/4/2024 3:59 PM, don Root wrote: Well Richard, then maybe yours was an S-38B? mark 2? or run2 or whatever ?
This below is snipped and edited from the BAMA _version B_ that I
downloaded some time back.
I know about what you are saying, my various versions are in deep
storage, and I believe? I have seen those backs on the D , but _why not
in the manuals_?
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Ahhh, now I get it, the ?SO-1 captured to the chassis while the PL-2 captured to the insulated back cover going down over the chassis apron Maybe the B C D E are all like that? But only B has it on the schematic. The A version lists only a line cord , and a poor pic of the chassis rear seems to show an attached cord to the chassis. For the S-38-C? and E? ,hidden in the parts list Is this: my snip image 
?..but only the B has it on the schematic ?it will be tough to properly add a 3-wire cord .. but that gets into a long story. ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Monday, November 4, 2024 7:24 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-38B, variations? This appears to be a photo with the back removed, note the tubes
visible. The mating connector is riveted to the back cover.
On 11/4/2024 3:59 PM, don Root wrote: Well Richard, then maybe yours was an S-38B? mark 2? or run2 or whatever ?
This below is snipped and edited from the BAMA _version B_ that I
downloaded some time back.
I know about what you are saying, my various versions are in deep
storage, and I believe? I have seen those backs on the D , but _why not
in the manuals_?
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998 ??
-- don??? va3drl
|
My S-38 is missing the back cover. The line cord comes from the
chassis through a gland, no sign of there ever having been a connector
there. Since I don't have the back cover I don't know for certain how it
was arranged but think the cord simply came through a hole in the cover
small enough to keep fingers out. However, it would have to have been
large enough to clear the line plug. Someone with an intact receiver
will have to answer.
I don't know what AC/DC receivers hallicrafters made before the
S-38. If we can include Echophone the EC-1 and EC-3 were AC/DC. Pictures
of the EC-3 show the line cord coming right out of the chassis.
There is some history to be found about the regulations applying to
AC/DC radios and phonographs. UL and other standards that might require
isolation of "hot" parts and approved methods of doing so. Of course,
Hallicrafters were not the only ones to make AC/DC gear so perhaps a
comparison with others might be enlightening.
toggle quoted message
Show quoted text
On 11/4/2024 4:54 PM, don Root wrote: Ahhh, now I get it, the ?SO-1 captured to the chassis while the PL-2
captured to the insulated back cover going down over the chassis apron
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
My S-38 (no suffix) with a metal bottom cover has no back cover, either.
The line cord comes through the chassis in what appears to be an
original round hole.
My Echophone EC-1A has a similar cord routed through a similar hole.
Its original back cover has a hole for the line cord to pass through
with a slot from the hole to the edge of the cover so that the cover can
be removed without bothering the line cord.
73,
Maynard
W6PAP
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Show quoted text
On 11/4/24 17:25, Richard Knoppow wrote: My S-38 is missing the back cover. The line cord comes from the
chassis through a gland, no sign of there ever having been a connector
there. Since I don't have the back cover I don't know for certain how it
was arranged but think the cord simply came through a hole in the cover
small enough to keep fingers out. However, it would have to have been
large enough to clear the line plug. Someone with an intact receiver
will have to answer.
I don't know what AC/DC receivers hallicrafters made before the
S-38. If we can include Echophone the EC-1 and EC-3 were AC/DC. Pictures
of the EC-3 show the line cord coming right out of the chassis.
There is some history to be found about the regulations applying to
AC/DC radios and phonographs. UL and other standards that might require
isolation of "hot" parts and approved methods of doing so. Of course,
Hallicrafters were not the only ones to make AC/DC gear so perhaps a
comparison with others might be enlightening.
On 11/4/2024 4:54 PM, don Root wrote:
Ahhh, now I get it, the ?SO-1 captured to the chassis while the PL-2
captured to the insulated back cover going down over the chassis apron
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
My S-38s (no suffix), EC-1s (no suffix) and S-41 all have a grommeted hole in the chassis for the line cord.? I can't get to my S-38C yet.
73,
Gary - W6GVS
toggle quoted message
Show quoted text
My S-38 (no suffix) with a metal bottom cover has no back cover, either.
The line cord comes through the chassis in what appears to be an
original round hole.
My Echophone EC-1A has a similar cord routed through a similar hole.
Its original back cover has a hole for the line cord to pass through
with a slot from the hole to the edge of the cover so that the cover can
be removed without bothering the line cord.
73,
Maynard
W6PAP
On 11/4/24 17:25, Richard Knoppow wrote:
My S-38 is missing the back cover. The line cord comes from the
chassis through a gland, no sign of there ever having been a connector
there. Since I don't have the back cover I don't know for certain how it
was arranged but think the cord simply came through a hole in the cover
small enough to keep fingers out. However, it would have to have been
large enough to clear the line plug. Someone with an intact receiver
will have to answer.
I don't know what AC/DC receivers hallicrafters made before the
S-38. If we can include Echophone the EC-1 and EC-3 were AC/DC. Pictures
of the EC-3 show the line cord coming right out of the chassis.
There is some history to be found about the regulations applying to
AC/DC radios and phonographs. UL and other standards that might require
isolation of "hot" parts and approved methods of doing so. Of course,
Hallicrafters were not the only ones to make AC/DC gear so perhaps a
comparison with others might be enlightening.
On 11/4/2024 4:54 PM, don Root wrote:
Ahhh, now I get it, the ?SO-1 captured to the chassis while the PL-2
captured to the insulated back cover going down over the chassis apron
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Richard, On Oct 28 ?????in topic ??Wanted: Schematic for S-38E ???you said “The C also shows a 470K resistor from the hot side of the switch to the cabinet ground. Not sure why. “?? see /g/HallicraftersRadios/message/31071 ? thanks for questioning this out loud.? Something was bothering me, ever since they lifted B-minus off the chassis. Now I think I have a clue, and I doubt the radio will work for long without that resistor. It is a good thing to understand, but takes some to understand all the modifications needed to convert a B to a C. You can find it I am sure.? -- don??? va3drl
|
I also saw that resistor and I also don't really understand why its
there. Is there an equivalent in the B? Its possible it has some effect
when the reciever is powered by DC or perhaps limits the voltage
possible on the cabinet through the RF capacitor. Considering all the
economies made I doubt it would be there unless necessary.
For the most part I have a healthy respect for Hallicrafters
engineering although its not always elegant.
toggle quoted message
Show quoted text
On 11/5/2024 10:04 AM, don Root wrote: Richard, On Oct 28 ?????in _topic ??Wanted: Schematic for S-38E_ ???you said
“The C also shows a 470K resistor from the hot side of the switch to the
cabinet ground. _Not sure why_.“?? see
/g/HallicraftersRadios/message/31071 <https://
groups.io/g/HallicraftersRadios/message/31071>
thanks for questioning this out loud.? Something was bothering me, ever
since they lifted B-minus off the chassis. Now I think I have a clue,
and I doubt the radio will work for long without that resistor. It is a
good thing to understand, but takes some to understand all the
modifications needed to convert a B to a C. You can find it I am sure.**
--
don??? va3drl
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Richard, I was quoting you? From Oct 28 RE “Is there an equivalent in the B?”? ?I would say NO. In version C ?they lifted B-minus off the chassis, but not really completely; one of the things that didn’t move is quite obvious on the drawings. I believe the resistor is part of the necessary change when ??version C moved B-minus off of the chassis. ?Without that 470k resistor in the C version [D,E too] one of the grids will float. I am trying to redraw part of the schematic to verify my thinking, in the mean time I don’t want to corrupt your thinking while you unravel the redesign. Too many people don’t see the changes, that halligan has hidden. ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Tuesday, November 5, 2024 1:47 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-38B, variations? I also saw that resistor and I also don't really understand why its
there. Is there an equivalent in the B? Its possible it has some effect
when the reciever is powered by DC or perhaps limits the voltage
possible on the cabinet through the RF capacitor. Considering all the
economies made I doubt it would be there unless necessary.
For the most part I have a healthy respect for Hallicrafters
engineering although its not always elegant.
On 11/5/2024 10:04 AM, don Root wrote: Richard, On Oct 28 ?????in _topic ??Wanted: Schematic for S-38E_ ???you said
“The C also shows a 470K resistor from the hot side of the switch to the
cabinet ground. _Not sure why_.“?? see
/g/HallicraftersRadios/message/31071 <https://
groups.io/g/HallicraftersRadios/message/31071>
thanks for questioning this out loud.? Something was bothering me, ever
since they lifted B-minus off the chassis. Now I think I have a clue,
and I doubt the radio will work for long without that resistor. It is a
good thing to understand, but takes some to understand all the
modifications needed to convert a B to a C. You can find it I am sure.**
--
don??? va3drl
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
-- don??? va3drl
|
See: Radiotron Designers Handbook, 4th Edition, page 1268, (C) Earth Connection
" Power units
and sets of the transformerless type shall have the live parts of the inner structure
isolated from the case or frame by an isolating condenser or other approved means,
which shall not be capable of passing a current exceeding 5 milliamperes to case or
frame when the full rated voltage is applied in the normal manner of operation." Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
Richard, I was quoting you? From Oct 28 RE “Is there an equivalent in the B?”? ?I would say NO. In version C ?they lifted B-minus off the chassis, but not really completely; one of the things that didn’t move is quite obvious on the drawings. I believe the resistor is part of the necessary change when ??version C moved B-minus off of the chassis. ?Without that 470k resistor in the C version [D,E too] one of the grids will float. I am trying to redraw part of the schematic to verify my thinking, in the mean time I don’t want to corrupt your thinking while you unravel the redesign. Too many people don’t see the changes, that halligan has hidden. ? ?
From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Tuesday, November 5, 2024 1:47 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-38B, variations ? I also saw that resistor and I also don't really understand why its
there. Is there an equivalent in the B? Its possible it has some effect
when the reciever is powered by DC or perhaps limits the voltage
possible on the cabinet through the RF capacitor. Considering all the
economies made I doubt it would be there unless necessary.
For the most part I have a healthy respect for Hallicrafters
engineering although its not always elegant.
On 11/5/2024 10:04 AM, don Root wrote: Richard, On Oct 28 ?????in _topic ??Wanted: Schematic for S-38E_ ???you said
“The C also shows a 470K resistor from the hot side of the switch to the
cabinet ground. _Not sure why_.“?? see
/g/HallicraftersRadios/message/31071 <https://
groups.io/g/HallicraftersRadios/message/31071>
thanks for questioning this out loud.? Something was bothering me, ever
since they lifted B-minus off the chassis. Now I think I have a clue,
and I doubt the radio will work for long without that resistor. It is a
good thing to understand, but takes some to understand all the
modifications needed to convert a B to a C. You can find it I am sure.**
--
don??? va3drl
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Jim, thanks for finding this In reading above this quote ?it says the quote was from the 1937 ?for Australia. I have been wondering when UL made and enforced similar statements. I looked and found almost nothing but around 1950 magazines advertised UL approved lightning arresters. Was UL giving quiet approval to radios all along?? … And that is just a question. Too bad we can’t find old UL standards ..even for household appliances ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Tuesday, November 5, 2024 5:01 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-38B, variations? See: Radiotron Designers Handbook, 4th Edition, page 1268, (C) Earth Connection " Power units and sets of the transformerless type shall have the live parts of the inner structure isolated from the case or frame by an isolating condenser or other approved means, which shall not be capable of passing a current exceeding 5 milliamperes to case or frame when the full rated voltage is applied in the normal manner of operation." Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy On Tuesday, November 5, 2024 at 02:06:02 PM CST, don Root <drootofallevil@...> wrote: Richard, I was quoting you? From Oct 28 RE “Is there an equivalent in the B?”? ?I would say NO. In version C ?they lifted B-minus off the chassis, but not really completely; one of the things that didn’t move is quite obvious on the drawings. I believe the resistor is part of the necessary change when ??version C moved B-minus off of the chassis. ?Without that 470k resistor in the C version [D,E too] one of the grids will float. I am trying to redraw part of the schematic to verify my thinking, in the mean time I don’t want to corrupt your thinking while you unravel the redesign. Too many people don’t see the changes, that halligan has hidden. ? ? ? -- don??? va3drl
|
There is a short history of UL at:
<>
I did search further but there rare many citations included in the
article, one of them may have information on when UL began to approve of
home radios. UL is a United States business but there are similar
organizations in Canada and elsewhere. It is NOT a government agency but
works with OSHA and others. It seems to me that my S38-B had a UL mark
on the back. Its gone now so I can't look. My S-38B was c.1949.
Non-consumer products, i.e. industrial electrical goods, do not
need UL approval, or didn't in the past, perhaps changed now since OSHA
has authority over them. Probably all on the web somewhere.
I suspect old UL standards are around if you do a thorough enough
search.
toggle quoted message
Show quoted text
On 11/5/2024 4:14 PM, don Root wrote: Jim, thanks for finding this
In reading *above *this quote ?it says the quote was from the 1937 ?for
Australia.
I have been wondering when UL made and enforced similar statements.
I looked and found almost nothing but around 1950 magazines advertised
UL approved lightning arresters.
Was UL giving quiet approval to radios all along?? … And that is just a
question.
Too bad we can’t find old UL standards ..even for household appliances
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
5mA is supposed to be the maximum "let go" current. Not sure if this
is still correct (I almost said current). The idea being that when you
grab something that causes greater current to flow in the body you can't
let go of it. Applies to AC, not DC. I just read a paper about this but
am not sure its up to date. The same paper says that the older research
assumed that body resistance was about 1500 ohms. Actually, its much
higher so probably the highest voltage on a surface allowed by the old
standard is much lower than necessary. Certainly, if I measure my body
resistance with an ohm meter I get a whole lot more than 1500 ohms.
toggle quoted message
Show quoted text
On 11/5/2024 2:01 PM, Jim Whartenby via groups.io wrote: See: Radiotron Designers Handbook, 4th Edition, page 1268, (C) Earth
Connection
" Power units and sets of the transformerless type shall have the live
parts of the inner structure isolated from the case or frame by an
isolating condenser or other approved means, which shall not be capable
of passing a current exceeding 5 milliamperes to case or frame when the
full rated voltage is applied in the normal manner of operation."
Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.
Murphy
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Richard, the link is sent previously from [UL solutions] gave the best info maybe but not enough to answer the questions. Some ads for PA Amplifiers had “underwriters” [UL ??] approval in ?1933 ?and ^^ pdf?? 12??? -----?? 
? 
?pdf? 33???? ----- ? Yes, in Canada, back in the 1930s HEPC [Hydro Electric Power Commission ?[of Ontario ] ] all powered radios apparently needed their approval ?Eventually ?that was taken over by CESA [Canadian Electrical Standards Association ]then CSA. ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Tuesday, November 5, 2024 9:46 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-38B, variations? There is a short history of UL at:
<>
I did search further but there rare many citations included in the
article, one of them may have information on when UL began to approve of
home radios. UL is a United States business but there are similar
organizations in Canada and elsewhere. It is NOT a government agency but
works with OSHA and others. It seems to me that my S38-B had a UL mark
on the back. Its gone now so I can't look. My S-38B was c.1949.
Non-consumer products, i.e. industrial electrical goods, do not
need UL approval, or didn't in the past, perhaps changed now since OSHA
has authority over them. Probably all on the web somewhere.
I suspect old UL standards are around if you do a thorough enough
search.
On 11/5/2024 4:14 PM, don Root wrote: Jim, thanks for finding this
In reading *above *this quote ?it says the quote was from the 1937 ?for
Australia.
I have been wondering when UL made and enforced similar statements.
I looked and found almost nothing but around 1950 magazines advertised
UL approved lightning arresters.
Was UL giving quiet approval to radios all along?? … And that is just a
question.
Too bad we can’t find old UL standards ..even for household appliances --
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998 -- don??? va3drl
|
The link I sent discusses the history of UL and mentions the
Canadian equivalent. UL is Underwriters' Laboratories, it is part of the
Fire Underwriters organization, which is a group set up by insurance
companies. Of course the idea is to help minimize the insurance losses
the member companies must suffer. Mostly makes things safer.
toggle quoted message
Show quoted text
On 11/7/2024 10:16 AM, don Root wrote: Richard, the link is sent previously from [UL solutions] gave the best
info maybe but not enough to answer the questions.
Some ads for PA Amplifiers had “underwriters” [UL ??] approval in ?1933 ?and
<>
^^
pdf?? 12??? -----
?pdf? 33???? -----
Yes, in Canada, back in the 1930s HEPC [Hydro Electric Power Commission
?[of Ontario ] ] all powered radios apparently needed their approval
?Eventually ?that was taken over by CESA [Canadian Electrical Standards
Association ]then CSA.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Richard and all ,later again Oh? whatever I thought I saw? must have been an apparition I took the time to copy ?the RF section of the B and C side by side? and now I have to agree with your “The C also shows a 470K resistor from the hot side of the switch to the cabinet ground. Not sure why. “?? At first I thought it was something to do with grid 3 bias, but now I see there is a new resistor tucked in there It seems that in the C version the Tune cap frame and rotor along with the chassis has RF ?floating above all else using capacitors while C24 provides the RF return to B-minus. I have run out of thinking power, but here is what I have been using recently. Do you spot anything? ?
? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of don Root
Sent: Tuesday, November 5, 2024 1:05 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] S-38B, variations? Richard, On Oct 28 ?????in topic ??Wanted: Schematic for S-38E ???you said “The C also shows a 470K resistor from the hot side of the switch to the cabinet ground. Not sure why. “?? see /g/HallicraftersRadios/message/31071 ? thanks for questioning this out loud.? Something was bothering me, ever since they lifted B-minus off the chassis. Now I think I have a clue, and I doubt the radio will work for long without that resistor. It is a good thing to understand, but takes some to understand all the modifications needed to convert a B to a C. You can find it I am sure.?
--
don??? va3drl
-- don??? va3drl
|
There is yet another resistor, in series with the capacitor to the
mixer signal grid. Not sure why these changes were made, evidently has
to do with the bias or with the change from a chassis ground to a
separate B return. Might help to draw out a simplified version of the
schematic.
The S-38 series seems to have been very popular, my B performed
quite well. I never had the National equivalent, the SW-54, but from
what I've read it was a dog. The neighbor who inpired me to get an S-38B
changed to an SW-54 but he was a rich kid who didn't really know
anything about radio. The SW-54 mechanical bandspread is supposed to be
just awful. They made only the one model while Hallicrafters kept poking
at the design.
toggle quoted message
Show quoted text
On 11/7/2024 2:46 PM, don Root wrote: Richard and all ,later again
Oh? whatever I thought I saw? must have been an apparition
I took the time to copy ?the RF section of the B and C side by side? and
now I have to agree with your
“The C also shows a 470K resistor from the hot side of the switch to the
cabinet ground. _Not sure why_.“
At first I thought it was something to do with grid 3 bias, but now I
see there is a new resistor tucked in there
It seems that in the C version the Tune cap frame and rotor along with
the chassis has RF ?floating above all else using capacitors while C24
provides the RF return to B-minus. I have run out of thinking power, but
here is what I have been using recently. Do you spot anything?
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Richard Are you referring to R21 and R24?? R21 is a return to ground for the AVC line and R24 is an isolating resistor between the tuning caps and the grid.? Both are used to increase stability.?? Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
There is yet another resistor, in series with the capacitor to the
mixer signal grid. Not sure why these changes were made, evidently has
to do with the bias or with the change from a chassis ground to a
separate B return. Might help to draw out a simplified version of the
schematic.
The S-38 series seems to have been very popular, my B performed
quite well. I never had the National equivalent, the SW-54, but from
what I've read it was a dog. The neighbor who inpired me to get an S-38B
changed to an SW-54 but he was a rich kid who didn't really know
anything about radio. The SW-54 mechanical bandspread is supposed to be
just awful. They made only the one model while Hallicrafters kept poking
at the design.
On 11/7/2024 2:46 PM, don Root wrote: Richard and all ,later again
Oh? whatever I thought I saw? must have been an apparition
I took the time to copy ?the RF section of the B and C side by side? and
now I have to agree with your
“The C also shows a 470K resistor from the hot side of the switch to the
cabinet ground. _Not sure why_.“
At first I thought it was something to do with grid 3 bias, but now I
see there is a new resistor tucked in there
It seems that in the C version the Tune cap frame and rotor along with
the chassis has RF ?floating above all else using capacitors while C24
provides the RF return to B-minus. I have run out of thinking power, but
here is what I have been using recently. Do you spot anything?
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
don Root
Jim Whartenby