S-38B Question
 

I've begun the restoration of an S-38B. Just started to replace the filters
an I already have a question. The old multi-section cap ground is connected
to pin 2 of the 35Z5 rather than directly to the chassis ground as shown in
the schematic he
http://i1206.photobucket.com/albums/...gFilterCap.png
Pin2 is connected to the chassis ground through the filament string, which
has a 125 ohm resistance when cold. Is this a problem or were all S38's
wired in this manner?

The filter cap appears to be original but you can't always be certain. It's
clear other repairs have been made during its lifetime.

If anyone can recall recapping an S-38 I'd be interested in your observation
regarding the filter cap ground wire location.

Thanks,

DaveW

S-38B Question
 

First, I don't have an answer, but am preparing to recap an even older S-38
myself. I think I remember
from many, many years ago, that some of those "hot chassis" rigs had two
ground systems, that were actually connected together at some point.
Something about "ground loops" and hum
reduction. In the schematic you linked here, there are two different ground
symbols. Could one be the actual chassis connection, and the other sort of a
slightly "lifted" or signal/RF ground? Just guessing, hope someone knows the
real answer!

Old Chief Lynn, W7LTQ


"DaveW" wrote in message
...
I've begun the restoration of an S-38B. Just started to replace the
filters an I already have a question. The old multi-section cap ground is
connected to pin 2 of the 35Z5 rather than directly to the chassis ground
as shown in the schematic he
http://i1206.photobucket.com/albums/...gFilterCap.png
Pin2 is connected to the chassis ground through the filament string, which
has a 125 ohm resistance when cold. Is this a problem or were all S38's
wired in this manner?

The filter cap appears to be original but you can't always be certain.
It's clear other repairs have been made during its lifetime.

If anyone can recall recapping an S-38 I'd be interested in your
observation regarding the filter cap ground wire location.

Thanks,

DaveW

S-38B Question
 

I checked the schematic notes and the inverted pyramid symbol is the chassis
ground. The other symbol is the cabinet ground. Apparently the chassis is
isolated from the cabinet except for a single 0.25 mfd capacitor which
connects the two.

DaveW


"coffelt2" wrote in message
...
First, I don't have an answer, but am preparing to recap an even older
S-38 myself. I think I remember
from many, many years ago, that some of those "hot chassis" rigs had two
ground systems, that were actually connected together at some point.
Something about "ground loops" and hum
reduction. In the schematic you linked here, there are two different
ground symbols. Could one be the actual chassis connection, and the other
sort of a slightly "lifted" or signal/RF ground? Just guessing, hope
someone knows the real answer!

Old Chief Lynn, W7LTQ


"DaveW" wrote in message
...
I've begun the restoration of an S-38B. Just started to replace the
filters an I already have a question. The old multi-section cap ground
is connected to pin 2 of the 35Z5 rather than directly to the chassis
ground as shown in the schematic he
http://i1206.photobucket.com/albums/...gFilterCap.png
Pin2 is connected to the chassis ground through the filament string,
which has a 125 ohm resistance when cold. Is this a problem or were all
S38's wired in this manner?

The filter cap appears to be original but you can't always be certain.
It's clear other repairs have been made during its lifetime.

If anyone can recall recapping an S-38 I'd be interested in your
observation regarding the filter cap ground wire location.

Thanks,

DaveW

S-38B Question
 

Yikes! That's why you could get quite a jolt just from the cabinet, and it
wasn't too cool
to use the S-38 right next to a grounded piece of gear. I think I remember
something in
QST "Hints and Kinks" about putting a light bulb (small wattage) between the
S-38's cabinet
and an adjacent, grounded piece of gear. If the lamp illuminated, reverse
the S-38's AC
wall plug.

Old Chief Lynn, W7LTQ


"DaveW" wrote in message
...
I checked the schematic notes and the inverted pyramid symbol is the
chassis ground. The other symbol is the cabinet ground. Apparently the
chassis is isolated from the cabinet except for a single 0.25 mfd capacitor
which connects the two.

DaveW


"coffelt2" wrote in message
...
First, I don't have an answer, but am preparing to recap an even older
S-38 myself. I think I remember
from many, many years ago, that some of those "hot chassis" rigs had two
ground systems, that were actually connected together at some point.
Something about "ground loops" and hum
reduction. In the schematic you linked here, there are two different
ground symbols. Could one be the actual chassis connection, and the other
sort of a slightly "lifted" or signal/RF ground? Just guessing, hope
someone knows the real answer!

Old Chief Lynn, W7LTQ


"DaveW" wrote in message
...
I've begun the restoration of an S-38B. Just started to replace the
filters an I already have a question. The old multi-section cap ground
is connected to pin 2 of the 35Z5 rather than directly to the chassis
ground as shown in the schematic he
http://i1206.photobucket.com/albums/...gFilterCap.png
Pin2 is connected to the chassis ground through the filament string,
which has a 125 ohm resistance when cold. Is this a problem or were all
S38's wired in this manner?

The filter cap appears to be original but you can't always be certain.
It's clear other repairs have been made during its lifetime.

If anyone can recall recapping an S-38 I'd be interested in your
observation regarding the filter cap ground wire location.

Thanks,

DaveW

S-38B Question
 

coffelt2 wrote:
Yikes! That's why you could get quite a jolt just from the cabinet, and it
wasn't too cool
to use the S-38 right next to a grounded piece of gear. I think I remember
something in
QST "Hints and Kinks" about putting a light bulb (small wattage) between the
S-38's cabinet
and an adjacent, grounded piece of gear. If the lamp illuminated, reverse
the S-38's AC
wall plug.

Back in my mispent youth, I took an S-38B which I had been given, and stuffed
a small 120v output AC transformer in it to use as an isolation transformer.

I also added a little bit of 1960's technology to it, I put two silicon diodes
in as a noise limiter.

In a fit of cleaning out, having long since gotten digital showrtwave radios,
in the 1980's I gave the radio away.

Geoff.
--
Geoffrey S. Mendelson, N3OWJ/4X1GM
My high blood pressure medicine reduces my midichlorian count. :-(

S-38B Question
 

On Sun, 11 Mar 2012, Geoffrey S. Mendelson wrote:

coffelt2 wrote:
Yikes! That's why you could get quite a jolt just from the cabinet, and it
wasn't too cool
to use the S-38 right next to a grounded piece of gear. I think I remember
something in
QST "Hints and Kinks" about putting a light bulb (small wattage) between the
S-38's cabinet
and an adjacent, grounded piece of gear. If the lamp illuminated, reverse
the S-38's AC
wall plug.

Back in my mispent youth, I took an S-38B which I had been given, and stuffed
a small 120v output AC transformer in it to use as an isolation transformer.

I also added a little bit of 1960's technology to it, I put two silicon diodes
in as a noise limiter.

In a fit of cleaning out, having long since gotten digital showrtwave radios,
in the 1980's I gave the radio away.

There was a story in "73" in the mid-sixties about someone trading in his
S38 for a better receiver (and obviously cash needed too). So the story
is basically about all the modifications he had to undo to put it back to
"normal". And right when he's at the store, he realizes he's forgotten
one mod, so he takes that out in the parking lot, I seem to recall having
to do some makeshift arrangement to cover the extra hole from that mod.

The isolation transformer wouldn't improve the receiver's ability to
receive one bit, but it sure made it a lot safer to use.

Michael

S-38B Question
 

On Sat, 10 Mar 2012 21:28:25 -0600, DaveW wrote:

I've begun the restoration of an S-38B. Just started to replace the
filters an I already have a question. The old multi-section cap ground
is connected to pin 2 of the 35Z5 rather than directly to the chassis
ground as shown in the schematic he
http://i1206.photobucket.com/albums/...watcher32/S38-
BFilamentStringFilterCap.png
Pin2 is connected to the chassis ground through the filament string,
which has a 125 ohm resistance when cold. Is this a problem or were all
S38's wired in this manner?

The filter cap appears to be original but you can't always be certain.
It's clear other repairs have been made during its lifetime.

If anyone can recall recapping an S-38 I'd be interested in your
observation regarding the filter cap ground wire location.

Thanks,

DaveW

I have never worked on an S-38 but I don't see how it could work wired
the way you described. Perhaps someone botched a recap job, couldn't
figure out why a new capacitor caused hum as bad or worse than the old
cap, and put it away for some future troubleshooting.

Are you sure you counted the pins correctly and that you are, indeed,
looking at the 35Z5 socket?

I checked a tube manual and your schematic shows the correct connections
for a 35Z5. The physical location of the capacitor's negative lead
should be where the wire from the switch connects to the chassis although
some other places are likely to work as well. The idea is to keep the
ripple current flowing through the capacitor from getting into other
circuits. The chassis has resistance and inductance and this current
causes voltage drops that can inject hum into sensitive circuits.

As others have mentioned, it's not the safest way to design a radio, but
it did work.

Good luck,

--
Jim Mueller

To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.

Just last week, I came across one for sale near Pittsburgh.
The owner bought it for $3.00 and was trying to sell it for $100.00

Before I approached him, I informed him about the floating ground issue and how the radio was dangerous and how it needed a transformer to make it more safe - due to the fact that it was designed for use with 120 VDC current not AC...

I could have bought it for $25.00 - but was unwilling to drive 120 miles to go pick it up.
When I stopped by a couple of days later - he had already sold it.

The radio is of little value - since it only did CW AM and has no SSB....
Just looking on Flea Bay tells me that they had issues with the cardboard on the rear of the radio - lot's of reproductions.

It would be ok if all you wanted it for was to listen to local traffic on the 11 meters - since it is mostly AM anyways!

S-38B Question
 

With all this discussion on the S 38 series, I wonder if everyone
knows about the S 38 website? http://www.the-s38-guy.com/ He has
some great information and hints. 73 Mike KF6KXG

S-38B Question
 

"Channel Jumper" wrote in message
...
Just last week, I came across one for sale near Pittsburgh.
The owner bought it for $3.00 and was trying to sell it for $100.00

Before I approached him, I informed him about the floating ground issue
and how the radio was dangerous and how it needed a transformer to make
it more safe - due to the fact that it was designed for use with 120 VDC
current not AC...

I could have bought it for $25.00 - but was unwilling to drive 120 miles
to go pick it up.
When I stopped by a couple of days later - he had already sold it.

The radio is of little value - since it only did CW AM and has no
SSB....
Just looking on Flea Bay tells me that they had issues with the
cardboard on the rear of the radio - lot's of reproductions.

It would be ok if all you wanted it for was to listen to local traffic
on the 11 meters - since it is mostly AM anyways!

Channel Jumper

.......and thus fully qualifies as a genuine BOATANCHOR!

Old Chief Lynn, W7LTQ (Let's hear it for the old S-38 !!!!!!!!!!!!!!)

S-38B Question
 

Channel Jumper wrote:

The radio is of little value - since it only did CW AM and has no
SSB....
Just looking on Flea Bay tells me that they had issues with the
cardboard on the rear of the radio - lot's of reproductions.

Sure it will do SSB! The BFO isn't adjustable, but the IF is wide as a
barn, wide enough that you can just set it on CW and then tune back and
forth until you get clear audio. Mind you it's unusable in a pileup...
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

S-38B Question
 

On Mon, 12 Mar 2012, Scott Dorsey wrote:

Channel Jumper wrote:

The radio is of little value - since it only did CW AM and has no
SSB....
Just looking on Flea Bay tells me that they had issues with the
cardboard on the rear of the radio - lot's of reproductions.

Sure it will do SSB! The BFO isn't adjustable, but the IF is wide as a
barn, wide enough that you can just set it on CW and then tune back and
forth until you get clear audio. Mind you it's unusable in a pileup...

Which was often the case for a lot of receivers. They had BFOs but
weren't so great when SSB came along, or required you to turn back the RF
gain a lot (so the BFO was strong compared to the incoming signal), which
made it relatively insensitive.

They weren't good receivers, but neither were a lot of low end ones back
then. But we bought them because we couldn't afford something better.

It wasn't a good choice, but a lot of people did start by shortwave
listening, so they got a general coverage receiver. A ham band only
receiver tended to be more expensive. So they had to live with a receiver
that wasn't particularly great for the ham bands, until they could
scrounge something better.

When I got my Hallicracter's S-120A in the summer of 1971, it was the
cheapest I could get, and almost more than I could afford, using up all
the birthday money saved in my relatively new bank account. It was junk,
not just cheap like the S38, but solid state and thus made worse because
the thing overloaded badly. But at the time, getting a ham license seemed
some years in the future, since at the time you had to be 15 or older to
get a license in Canada. So I bought that receiver, and never got much
out of it. At least it wsa a time when there were lots of SW broadcast
sttions, and I could thrill to WWV on six frequencies. And yes, it did
"well" on CB, because there were local signals, and when the band opened
up, it was wall to wall heterodynes.

It didn't do SSB, until I put a potentiometer between the antenna and the
antenna terminals and reduced signals so the BFO was strong enough,
leaving very few signals that were strong enough. But it wsa a period
when there were some AM stations, I thought at the time they were younger
and doing AM as "something new" but maybe not, maybe they just never
switched to SSB. So I could listen to them every night on 80m and it was
sort of what ham radio must have sounded like in earlier decades.

And then five months later, I read in the paper that the law was changing,
so you didn't need to be fifteen to get a ham license in Canada.

I couldn't use that receiver for CW, not enough selectivity, so I was
reduced to a record to learn the code. And then I was lucky, someone at
the ham club when I finally found it lent me an SP-600 (I had it for about
a decade), so I actually had a decent receiver. (It didn't do anything
differently than the S-120A when it came to SSB either, except it was a
much better receiver, much more sensitive and of course more selective, so
when I turned down the RF gain to use the BFO properly, there were still
plenty of SSB signals to receive.

Michael VE2BVW

S-38B Question
 

"Scott Dorsey" wrote in message
...
Channel Jumper wrote:

The radio is of little value - since it only did CW AM and has no
SSB....
Just looking on Flea Bay tells me that they had issues with the
cardboard on the rear of the radio - lot's of reproductions.

Sure it will do SSB! The BFO isn't adjustable, but the IF is wide as a
barn, wide enough that you can just set it on CW and then tune back and
forth until you get clear audio. Mind you it's unusable in a pileup...
--scott

Bought my FIRST S-38 from the base exchange at Amarillo AFB, Tx, in
1951.
It was small enough to fit under my bunk, behind my lined up (and shined)
shoes. I was
already a ham, but Uncle Sam had better things for me to do!
Don't remember when I parted with that little Honey, but the following
year, 1952,
in the barracks in Germany, I built Heathkit's AR-1 (or was it AR-2?). A
crowd gathered
when I first plugged it in. A little curl of smoke from a resistor had them
all laughing, but
then loud music erupted, and there were cheers!
Now, a couple of years later, I found a maybe 6 of 10, 6 tube S-38. I
haven't got
my new cardboard back or bottom yet, but knobs are perfect. Some Gentleman
in the
Midwest is selling capacitor (condensers, really) kits, which I have. (for
three years)
Rome was not built in a day.

Old Chief Lynn, W7LTQ

S-38B Question
 

On 3/13/2012 3:08 AM, coffelt2 wrote:
snip Some Gentleman in the
Midwest is selling capacitor (condensers, really) kits,
which I have. (for three years)
Rome was not built in a day.

Old Chief Lynn, W7LTQ

Hi,

You're probably thinking of "Hayseed Hamfest":
http://www.hayseedhamfest.com/capaci...rafters_1.html

I've only heard heard good things about him, but I'm not yet a customer.

73,
Ed Knobloch

S-38B Question
 

"Edward Knobloch" wrote in message
...
On 3/13/2012 3:08 AM, coffelt2 wrote:
snip Some Gentleman in the
Midwest is selling capacitor (condensers, really) kits,
which I have. (for three years)
Rome was not built in a day.

Old Chief Lynn, W7LTQ

Hi,

You're probably thinking of "Hayseed Hamfest":
http://www.hayseedhamfest.com/capaci...rafters_1.html

I've only heard heard good things about him, but I'm not yet a customer.

73,
Ed Knobloch


Thanks, ED, I see he has a kit for my NC-183D! Glad you pointed out
his website. I had completely forgotten who that was. Got three kits
from him several years ago, and couldn't have been more pleased.

(No connection with him except purchases)

Old Chief Lynn, W7LTQ

S-38B Question
 

"Edward Knobloch" wrote in message
...
On 3/13/2012 3:08 AM, coffelt2 wrote:
snip Some Gentleman in the
Midwest is selling capacitor (condensers, really) kits,
which I have. (for three years)
Rome was not built in a day.

Old Chief Lynn, W7LTQ

Hi,

You're probably thinking of "Hayseed Hamfest":
http://www.hayseedhamfest.com/capaci...rafters_1.html

I've only heard heard good things about him, but I'm not
yet a customer.

73,
Ed Knobloch

I've gotten several can capacitors from Tom, excellent
parts. These are brand new, not re-stuffed old cans and not
old stock.
FWIW, the S-38B is essentially a five-tube wonder
adapted to short wave. My first receiver was an S-38B which
I still have. Its performance is certainly limited but it
works well for what it is. It _will_ receive SSB with
careful tuning and if the signal is not too strong. The RF
gain is not adjustable. The S-38B and later versions uses a
patented feedback arrangement for the BFO where the IF stage
is made to oscillate. The BFO frequency is approximately
centered on the IF frequency and is not adjustable.
The original S-38 used a different circuit with a
separate BFO tube, it also had a noise limiter.
Hallicrafters had a target price of around $50 but the
rather rapid inflation of the time required re-design and
simplification to maintain the price. National's
competition was the SW-54. I've never had one so can't
compare the two. The SW-54 used miniature tubes but the
tubes in the S-38B were the latest octals so there might not
have been any advantage. A lot of the performance would be
determined by the quality of the coils and general
construction. The SW-54 was also an AC/DC rig. Part of this
was simply to save the cost of a power transformer but also
some parts of some cities still had DC current supplied to
homes and especially industrial areas.
My S-38B was a good friend for a long time.


--

--
Richard Knoppow
Los Angeles
WB6KBL