Stewart-Warner reactance dimmer

[Dave Burson]

S-W model R-1822 has a "reactance dimmer" (item 2) with a 6.3 v lamp that
illuminates the band indicators. The bandswitch physically moves the
nameplates over the lamp. The transformer primary appears to be open, and a
10K resistor across it does provide a little signal to the speaker. C21 &
C14 are listed as 10 mfd, 25 v and 0.1 mfd, 150 v, and both are absent. I
am suspicious that C21 of that value doesn't belong, since the schematic has
misidentified a C22 elsewhere. Schematic is from Nostalgia Air.
This radio had been severely hacked, but the beautiful cabinet has kept me
picking away at it for a long time.
I've found a little about reactance dimmers but nothing about use in a tube
radio, mostly fluorescent dimmers. I'd really appreciate any explanation of
the function here and especially thoughts about the caps that parallel the
primary.

Thanks,
Dave Burson

[Randy or Sherry Guttery]

Dave Burson wrote:

> S-W model R-1822 has a "reactance dimmer" (item 2) with a 6.3 v lamp that
> illuminates the band indicators. The bandswitch physically moves the
> nameplates over the lamp. The transformer primary appears to be open, and a
> 10K resistor across it does provide a little signal to the speaker. C21 &
> C14 are listed as 10 mfd, 25 v and 0.1 mfd, 150 v, and both are absent. I
> am suspicious that C21 of that value doesn't belong, since the schematic has
> misidentified a C22 elsewhere. Schematic is from Nostalgia Air.
> This radio had been severely hacked, but the beautiful cabinet has kept me
> picking away at it for a long time.
> I've found a little about reactance dimmers but nothing about use in a tube
> radio, mostly fluorescent dimmers. I'd really appreciate any explanation of
> the function here and especially thoughts about the caps that parallel the
> primary.

What this appears to be is a saturable reactor who's input is the B+
current to the RF/IF stages - which means the less signal strength - the
higher the B+ current - due to AGC bias action.

This is the same idea that "drives" the Philco shadow meter. Low signal
- high current - since the AGC is low - and biases the tube more "on".
Signal strength comes up (as a station is tuned in) AGC goes negative,
turning the RF & IF tubes "down" (less current). As the current through
the primary rises and falls - so does the saturation - effecting the
transformer's coupling.

Now notice the two secondary windings- If the transformer's "coupling"
is working well - the two windings "buck" - the lamp is dim. However -
if the transformer's coupling isn't - the two windings "interaction" is
reduced - and the lamp is brighter.

Oh, the two caps - well the last thing you want is for the AC signal on
the secondary to be "coupled" through to the B+ - so the two caps act as
bypasses to keep the 60 cycle out of the B+.

(shooting from the hip - again - (sigh) - OK guys - what'd I miss?

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Ken]

Randy or Sherry Guttery wrote:
> Dave Burson wrote:
>
>> S-W model R-1822 has a "reactance dimmer" (item 2) with a 6.3 v lamp
>> that illuminates the band indicators. The bandswitch physically moves
>> the nameplates over the lamp. The transformer primary appears to be
>> open, and a 10K resistor across it does provide a little signal to the
>> speaker. C21 & C14 are listed as 10 mfd, 25 v and 0.1 mfd, 150 v, and
>> both are absent. I am suspicious that C21 of that value doesn't
>> belong, since the schematic has misidentified a C22 elsewhere.
>> Schematic is from Nostalgia Air.
>> This radio had been severely hacked, but the beautiful cabinet has
>> kept me picking away at it for a long time.
>> I've found a little about reactance dimmers but nothing about use in a
>> tube radio, mostly fluorescent dimmers. I'd really appreciate any
>> explanation of the function here and especially thoughts about the
>> caps that parallel the primary.
>
> What this appears to be is a saturable reactor who's input is the B+
> current to the RF/IF stages - which means the less signal strength - the
> higher the B+ current - due to AGC bias action.
>
> This is the same idea that "drives" the Philco shadow meter. Low signal
> - high current - since the AGC is low - and biases the tube more "on".
> Signal strength comes up (as a station is tuned in) AGC goes negative,
> turning the RF & IF tubes "down" (less current). As the current through
> the primary rises and falls - so does the saturation - effecting the
> transformer's coupling.
>
> Now notice the two secondary windings- If the transformer's "coupling"
> is working well - the two windings "buck" - the lamp is dim. However -
> if the transformer's coupling isn't - the two windings "interaction" is
> reduced - and the lamp is brighter.
>
> Oh, the two caps - well the last thing you want is for the AC signal on
> the secondary to be "coupled" through to the B+ - so the two caps act as
> bypasses to keep the 60 cycle out of the B+.
>
> (shooting from the hip - again - (sigh) - OK guys - what'd I miss?
>
> best regards...
So with high B+ current, the xfmr is saturated, less bucking, lamp is
bright? That means the bulb dims when on station? Ken

[Uncle Peter]

"Ken" > wrote in message
...
> Randy or Sherry Guttery wrote:
>> Dave Burson wrote:
>> >> best regards...
> So with high B+ current, the xfmr is saturated, less bucking, lamp is
> bright? That means the bulb dims when on station? Ken

Core saturates, and windings lose their inductance, basically becoming
purely resistive (only the wire winding DC resistance with no reactance),
the light would be brighter.

Pee

[John Byrns[_2_]]

In article >,
Randy or Sherry Guttery > wrote:

> Dave Burson wrote:
>
> > S-W model R-1822 has a "reactance dimmer" (item 2) with a 6.3 v lamp that
> > illuminates the band indicators. The bandswitch physically moves the
> > nameplates over the lamp. The transformer primary appears to be open, and
> > a
> > 10K resistor across it does provide a little signal to the speaker. C21 &
> > C14 are listed as 10 mfd, 25 v and 0.1 mfd, 150 v, and both are absent. I
> > am suspicious that C21 of that value doesn't belong, since the schematic
> > has
> > misidentified a C22 elsewhere. Schematic is from Nostalgia Air.
> > This radio had been severely hacked, but the beautiful cabinet has kept me
> > picking away at it for a long time.
> > I've found a little about reactance dimmers but nothing about use in a tube
> > radio, mostly fluorescent dimmers. I'd really appreciate any explanation
> > of
> > the function here and especially thoughts about the caps that parallel the
> > primary.
>
> What this appears to be is a saturable reactor who's input is the B+
> current to the RF/IF stages - which means the less signal strength - the
> higher the B+ current - due to AGC bias action.
>
> This is the same idea that "drives" the Philco shadow meter. Low signal
> - high current - since the AGC is low - and biases the tube more "on".
> Signal strength comes up (as a station is tuned in) AGC goes negative,
> turning the RF & IF tubes "down" (less current). As the current through
> the primary rises and falls - so does the saturation - effecting the
> transformer's coupling.
>
> Now notice the two secondary windings- If the transformer's "coupling"
> is working well - the two windings "buck" - the lamp is dim. However -
> if the transformer's coupling isn't - the two windings "interaction" is
> reduced - and the lamp is brighter.
>
> Oh, the two caps - well the last thing you want is for the AC signal on
> the secondary to be "coupled" through to the B+ - so the two caps act as
> bypasses to keep the 60 cycle out of the B+.
>
> (shooting from the hip - again - (sigh) - OK guys - what'd I miss?

This circuit is very confusing to me, I don't understand how it is
supposed to work. There seem to be two opposing forces at work in the
saturable transformer. The first is what you point out, that the two
secondary windings are connected so they "buck", so that when the
transformer is saturated by the DC in the primary, the coupling
decreases and the light dims. But at the same time when the transformer
is saturated the inductance also goes down, so even though the two
secondary windings might be not coupled as tightly, their reactance is
also lower which would tend to cause the light to become brighter. If
this is all there is to it the question would be which one of the two
effects is stronger than the other?

But maybe the windings aren't arranged as on an ordinary transformer.
What if we had E-core style laminations with the primary wound on the
center leg and one of the two secondaries wound on each outer leg. The
presence of the center leg would act as a magnetic short and greatly
reduce the coupling between the two secondaries even when the
transformer isn't saturated. When the transformer isn't saturated the
light would be dim because of the high reactance of the two secondaries
in series with the light. When the transformer becomes saturated at low
signal levels the lights would become brighter because of the lowered
reactance of the two secondary halves.

Just another shot from the hip, it would be interesting to know what the
actual disposition of the primary and secondary windings on the the
transformer core is?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

In article >,
"Uncle Peter" > wrote:

> "Ken" > wrote in message
> ...
> > Randy or Sherry Guttery wrote:
> >> Dave Burson wrote:
> >> >> best regards...
> > So with high B+ current, the xfmr is saturated, less bucking, lamp is
> > bright? That means the bulb dims when on station? Ken
>
> Core saturates, and windings lose their inductance, basically becoming
> purely resistive (only the wire winding DC resistance with no reactance),
> the light would be brighter.

The problem with this explanation is that the two secondaries appear to
be connected so that they "buck" one another. If that is the actual
case then the reactance of the two series connected secondary windings
wouldn't change much with transformer saturation.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Randy or Sherry Guttery]

John Byrns wrote:

> The problem with this explanation is that the two secondaries appear to
> be connected so that they "buck" one another. If that is the actual
> case then the reactance of the two series connected secondary windings
> wouldn't change much with transformer saturation.

Yes, I agree - I think its more of the coupling increasing and
decreasing causing more or less bucking between the windings. The
decrease in inductance (at 60 cycle) would not be near as influential as
the loss of coupling... Then again - as you noted - physical layout
could have very significant impact on both / either... hmmmm...

It is an interesting application. Didn't GE have something like this in
some of their consoles? I've never had one in for service - but it seems
I recall reading something about them.

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Randy or Sherry Guttery]

John Byrns wrote:


> Just another shot from the hip, it would be interesting to know what the
> actual disposition of the primary and secondary windings on the the
> transformer core is?

Oh good heavens, John, how reckless - shooting from the hip... I'm
proud of you! ;-)

We had a circuit that was similar in a piece of RADAR gear - IIRC the
transformer was pretty standard looking (but then it's been 30+ years).
I think the key here is the the phasing of the two secondaries - with
the core approaching saturation - the mutual coupling would decrease (as
would the inductance itself) and since the phasing is opposed - both
tend to incease the bulb's current...

Am I missing something?
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Dave Burson]

> This circuit is very confusing to me, I don't understand how it is
> supposed to work. There seem to be two opposing forces at work in the
> saturable transformer. The first is what you point out, that the two
> secondary windings are connected so they "buck", so that when the
> transformer is saturated by the DC in the primary, the coupling
> decreases and the light dims. But at the same time when the transformer
> is saturated the inductance also goes down, so even though the two
> secondary windings might be not coupled as tightly, their reactance is
> also lower which would tend to cause the light to become brighter. If
> this is all there is to it the question would be which one of the two
> effects is stronger than the other?
>
> But maybe the windings aren't arranged as on an ordinary transformer.
> What if we had E-core style laminations with the primary wound on the
> center leg and one of the two secondaries wound on each outer leg. The
> presence of the center leg would act as a magnetic short and greatly
> reduce the coupling between the two secondaries even when the
> transformer isn't saturated. When the transformer isn't saturated the
> light would be dim because of the high reactance of the two secondaries
> in series with the light. When the transformer becomes saturated at low
> signal levels the lights would become brighter because of the lowered
> reactance of the two secondary halves.
>
> Just another shot from the hip, it would be interesting to know what the
> actual disposition of the primary and secondary windings on the the
> transformer core is?
>
>
> Regards,
>
> John Byrns
>
> --
> Surf my web pages at, http://fmamradios.com/

This may not shed light, since the drawing quality is poor, but there is a
connection detail for the dimmer.

I still don't understand the need for 2 caps of such different values and
voltage ratings.

Dave Burson

[Ken]

Uncle Peter wrote:
> "Ken" > wrote in message
> ...
>> Randy or Sherry Guttery wrote:
>>> Dave Burson wrote:
>>> >> best regards...
>> So with high B+ current, the xfmr is saturated, less bucking, lamp is
>> bright? That means the bulb dims when on station? Ken
>
> Core saturates, and windings lose their inductance, basically becoming
> purely resistive (only the wire winding DC resistance with no reactance),
> the light would be brighter.
>
> Pee
>
>
But the core saturates on high current, that's off station. So the light
is bright off station and dim on. It would make sense to have the lamp
brighten on station, but I have seen other schemes work like this. Ken

[Randy or Sherry Guttery]

Dave Burson wrote:

> I still don't understand the need for 2 caps of such different values and
> voltage ratings.

Has to do with the caps themselves. The large cap is for the 60 cycles
(actually 50 to 133 cycles); while the smaller cap is for higher
frequencies. I didn't see the power supply schematic - but dimes to
donuts it's full wave- so the ripple frequency is double the AC line
(110 to 120). That's likely to be phase-shifted a bit before reaching
this circuit. The lamp runs on line frequency - and in combination with
the ripple (riding on the B+) it'd be easy to generate some rather
complex waveforms - with some pretty high harmonics. The large cap
"eats" the lower frequncies - however - it's construction limits it's
usefulness at higher frequencies - so there is the smaller one to deal
with those. Look at most any power supply - you'll find smaller value
caps by-passing the main filters.

The voltage is insignificant (within reason). I'm sure the 25V was
overkill (likely the highest voltage across the primary was 10V); but
25V was "common" back then (often found as the output tube cathode
bypass cap). Since a .1 is seldom seen in lower than 150V - that value
was probably stocked on the shelf as well. Even today - most .1 - even
in solid state stuff - are seldom less than 50V. Just a matter of what
was already on hand (big quantities of a common value are cheaper than a
few "special" values even if those special values could be smaller).


best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Brenda Ann]

"John Byrns" > wrote in message
...

<Interesting stuff... snipped for brevity. >

I'm a neophyte to this circuit, but let me posit a thought.

Perhaps the fact the secondarys being wired in bucking fashion has not as
much to do with the function of the circuit itself as to assist in the
prevention of the AC filament voltage from being introduced into the plate
supply for the 1st. detector and 1st. IF (otherwise it seems to me it would
make a rather effective modulation transformer). Also, it seems to me that
I've seen other radios (if not the specific circuitry therein) that had
tuning lamps that dimmed when tuned on station. I can think of a couple
reasons for this. First and foremost, more light is needed when tuning
across the dial than when on station. Also, this would tend to cause the
dial lamp to last a considerably longer time than normal, since when on
station it would be running at a fraction of it's normal voltage.

On the other hand, when DC saturates the secondary, wouldn't that tend to
make the primary look like a direct short?

[Randy or Sherry Guttery]

Brenda Ann wrote:

> Perhaps the fact the secondarys being wired in bucking fashion has not as
> much to do with the function of the circuit itself as to assist in the
> prevention of the AC filament voltage from being introduced into the plate
> supply for the 1st. detector and 1st.

No, the phasing of the two winding to be bucking IS the purpose of the
circuit, and how it works.


> IF (otherwise it seems to me it would
> make a rather effective modulation transformer).

Still would - that's what those capacitors across the primary are for.


> On the other hand, when DC saturates the secondary, wouldn't that tend to
> make the primary look like a direct short?

There is no dc in the secondary - only the primary (the primary is to
the right in this circuit). Remember TRANSFORMERS by nature are designed
to operate on AC; DC only "messes them up". In this case - this circuit
is intentionally designed to take advantage of that.

Let's walk through it one more time - but this time secondaries first -
then primary.

First - let's think about the two (secondary) windings as a primary and
secondary - after all - what windings are "called" has to due with their
use, nothing more. If you hooked AC directly to one winding and a bulb
directly to the other - the AC would couple from one winding to the
other and light the bulb (leaving aside current density, etc. for the
moment). If the two windings are 1:1 ratio - 6.3V applied to one would
show up as 6.3V on the other. You could wire the bulb either way (i.e.
"turn it around") and the current would flow through either the same
phase as the primary (ignoring simple inductance) - or 180 degrees "out
of phase". Point being - the two windings are the same - both oriented
on the same core - and form a 1:1 ratio between them. As long as the
core works as a transformer - the voltage couple between them will be
(ignoring losses) 1:1 - the only "variable" would be the phasing - as
determined by how the windings are hooked up.

OK - now lets wire the two windings as shown in the schematic: Both
windings on the same core; both having "equal effect" (1:1). Now when
current (attempts) to pass through one winding - it "couples" to the
other winding - which then generates an equal (but because of phasing)
but opposite voltage - which tends to cancel (buck) the voltage applied
to the first winding. Think of it as two batteries. If two batteries
are wired "nose to nose" with a bulb in series with them - what happens
to the bulb? Nothing. The two voltage "buck" each other - and (provided
the batteries have an equal charge) equilibrium is reached - no current
flows. Same thing with our two windings - WHEN the transformer's
ability to couple is un-imparied.

This "wild card" then - is what makes the circuit useful. This
particular "transformer" is a special kind which unlike the "usual"
transformer (which has modifications to help it "ignore" DC in the
windings) - but rather is designed to indeed easily saturate the core
when (sufficient) DC passes through one of it's windings. As the core of
a transformer approaches saturation - it's ability to couple AC between
the windings starts to fail; to the point that a fully saturated core
couples virtually nothing.

So - in this circuit - when the AGC has the RF / IF stages biased way
down (on station) the B+ current draw is low - which passing through the
primary (or control winding if you prefer) has little effect on the
transformer's ability to couple AC between the other windings - in this
case causing one winding to "buck" the other - and the bulb is dim.
When the AGC falls - biasing up the gain (current) of the RF & IF stages
- the current in the primary (or control) winding increases - pushing
the core towards saturation - and the two windings in series with the
bulb loose their coupling, reducing the induced bucking emf - and the
bulb brightens.

As you noted - when there is significant coupling between the two bulb
windings - that will also couple to the primary (or control) winding.
That's where the two capacitors come into play - they bypass any ripple
impressed on that winding back down to the B+ rail - which of course has
it's own filtering to ground.

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Ken]

Randy or Sherry Guttery wrote:
> Brenda Ann wrote:
>
>> Perhaps the fact the secondarys being wired in bucking fashion has not
>> as much to do with the function of the circuit itself as to assist in
>> the prevention of the AC filament voltage from being introduced into
>> the plate supply for the 1st. detector and 1st.
>
> No, the phasing of the two winding to be bucking IS the purpose of the
> circuit, and how it works.
>
>
>> IF (otherwise it seems to me it would make a rather effective
>> modulation transformer).
>
> Still would - that's what those capacitors across the primary are for.
>
>
>> On the other hand, when DC saturates the secondary, wouldn't that tend
>> to make the primary look like a direct short?
>
> There is no dc in the secondary - only the primary (the primary is to
> the right in this circuit). Remember TRANSFORMERS by nature are designed
> to operate on AC; DC only "messes them up". In this case - this circuit
> is intentionally designed to take advantage of that.
>
> Let's walk through it one more time - but this time secondaries first -
> then primary.
>
> First - let's think about the two (secondary) windings as a primary and
> secondary - after all - what windings are "called" has to due with their
> use, nothing more. If you hooked AC directly to one winding and a bulb
> directly to the other - the AC would couple from one winding to the
> other and light the bulb (leaving aside current density, etc. for the
> moment). If the two windings are 1:1 ratio - 6.3V applied to one would
> show up as 6.3V on the other. You could wire the bulb either way (i.e.
> "turn it around") and the current would flow through either the same
> phase as the primary (ignoring simple inductance) - or 180 degrees "out
> of phase". Point being - the two windings are the same - both oriented
> on the same core - and form a 1:1 ratio between them. As long as the
> core works as a transformer - the voltage couple between them will be
> (ignoring losses) 1:1 - the only "variable" would be the phasing - as
> determined by how the windings are hooked up.
>
> OK - now lets wire the two windings as shown in the schematic: Both
> windings on the same core; both having "equal effect" (1:1). Now when
> current (attempts) to pass through one winding - it "couples" to the
> other winding - which then generates an equal (but because of phasing)
> but opposite voltage - which tends to cancel (buck) the voltage applied
> to the first winding. Think of it as two batteries. If two batteries
> are wired "nose to nose" with a bulb in series with them - what happens
> to the bulb? Nothing. The two voltage "buck" each other - and (provided
> the batteries have an equal charge) equilibrium is reached - no current
> flows. Same thing with our two windings - WHEN the transformer's
> ability to couple is un-imparied.
>
> This "wild card" then - is what makes the circuit useful. This
> particular "transformer" is a special kind which unlike the "usual"
> transformer (which has modifications to help it "ignore" DC in the
> windings) - but rather is designed to indeed easily saturate the core
> when (sufficient) DC passes through one of it's windings. As the core of
> a transformer approaches saturation - it's ability to couple AC between
> the windings starts to fail; to the point that a fully saturated core
> couples virtually nothing.
>
> So - in this circuit - when the AGC has the RF / IF stages biased way
> down (on station) the B+ current draw is low - which passing through the
> primary (or control winding if you prefer) has little effect on the
> transformer's ability to couple AC between the other windings - in this
> case causing one winding to "buck" the other - and the bulb is dim. When
> the AGC falls - biasing up the gain (current) of the RF & IF stages -
> the current in the primary (or control) winding increases - pushing the
> core towards saturation - and the two windings in series with the bulb
> loose their coupling, reducing the induced bucking emf - and the bulb
> brightens.
>
> As you noted - when there is significant coupling between the two bulb
> windings - that will also couple to the primary (or control) winding.
> That's where the two capacitors come into play - they bypass any ripple
> impressed on that winding back down to the B+ rail - which of course has
> it's own filtering to ground.
>
> best regards...
So, what is the design method for a transformer that saturates easily? Ken

[Randy or Sherry Guttery]

Ken wrote:

> So, what is the design method for a transformer that saturates easily?

Without getting into a bunch of formulae, etc. (which I'd probably screw
up anyway)... a couple of factors - 1) absolute minimum core to couple
the windings - i.e. magnetically "starved". 2) no gaps in the core - let
the DC current's field circulate well - such that it "interferes" with
the AC field. The core can only hold so much flux - if DC is "pushing"
the field one way -- the AC (when it opposes) is only going to "reduce"
it - not reverse it - (or not fully reverse it) so that the coupling
becomes very inefficient. If you look at most output transformers
designed for single-ended use - they have a gap in the core somewhere.
Obviously - such a gap would not be appropriate for a saturable reactor.

And that sets me pondering again whether the primary "effect" is bucking
or just reactance... Let's say for the moment that bucking is not the
primary mode - and reactance is. Then why the reversed phasing (if
bucking isn't a factor)?

Well - as I just noted - in a true saturable reactor - the DC flux
"overwhelms" the AC flux. Since the AC and DC are additive half the
time - and subtractive half the time - the control isn't going to be
symmetrical. This is overcome in "the real world" by twin reactors -
with the DC "reversed" through one (compared to the other). This way
the "offset" in one reactor is "countered" by the other --- and then
they "switch roles" when the AC reverses polarity. If you look at the
circuit here - (and again - for discussion sake totally ignore bucking)
- the AC is "reversed" all the time at one end - or the other of the
primary -- as the two coils are phase reversed.

Back to saturable reactor theory - when the DC control winding drives
the core into saturation - the reactance in the AC winding drops
dramatically. That being the case with this circuit - then the two
windings would 1) loose coupling so bucking is no longer a factor - and
2) have virtually no reactance in series with the bulb. Then by 1/2 the
AC "reactance winding" reversed - both halves would contribute their
part to the overall source impedance - providing better symmetry.

Now I'm not so sure that pure reactance doesn't play a larger role than
originally thought... That perhaps control is indeed more reactance -
and "bucking" is just a happy "bonus" to the equation...

without taking some measurements (esp. being able to Un-reverse phase
the two windings) - it's hard to guess...

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[John Byrns[_2_]]

In article >,
Randy or Sherry Guttery > wrote:

> Ken wrote:
>
> > So, what is the design method for a transformer that saturates easily?
>
> Without getting into a bunch of formulae, etc. (which I'd probably screw
> up anyway)... a couple of factors - 1) absolute minimum core to couple
> the windings - i.e. magnetically "starved". 2) no gaps in the core - let
> the DC current's field circulate well - such that it "interferes" with
> the AC field. The core can only hold so much flux - if DC is "pushing"
> the field one way -- the AC (when it opposes) is only going to "reduce"
> it - not reverse it - (or not fully reverse it) so that the coupling
> becomes very inefficient. If you look at most output transformers
> designed for single-ended use - they have a gap in the core somewhere.
> Obviously - such a gap would not be appropriate for a saturable reactor.
>
> And that sets me pondering again whether the primary "effect" is bucking
> or just reactance... Let's say for the moment that bucking is not the
> primary mode - and reactance is. Then why the reversed phasing (if
> bucking isn't a factor)?
>
> Well - as I just noted - in a true saturable reactor - the DC flux
> "overwhelms" the AC flux. Since the AC and DC are additive half the
> time - and subtractive half the time - the control isn't going to be
> symmetrical. This is overcome in "the real world" by twin reactors -
> with the DC "reversed" through one (compared to the other). This way
> the "offset" in one reactor is "countered" by the other --- and then
> they "switch roles" when the AC reverses polarity. If you look at the
> circuit here - (and again - for discussion sake totally ignore bucking)
> - the AC is "reversed" all the time at one end - or the other of the
> primary -- as the two coils are phase reversed.
>
> Back to saturable reactor theory - when the DC control winding drives
> the core into saturation - the reactance in the AC winding drops
> dramatically. That being the case with this circuit - then the two
> windings would 1) loose coupling so bucking is no longer a factor - and
> 2) have virtually no reactance in series with the bulb. Then by 1/2 the
> AC "reactance winding" reversed - both halves would contribute their
> part to the overall source impedance - providing better symmetry.
>
> Now I'm not so sure that pure reactance doesn't play a larger role than
> originally thought... That perhaps control is indeed more reactance -
> and "bucking" is just a happy "bonus" to the equation...

Is one or the other really necessarily a "bonus", don't they work in
opposite directions assuming the two windings are connected in a
"bucking" configuration? Of course we don't actually know they are
really connected in a "bucking" configuration, we are just speculating
they are because of the way the schematic is drawn.

> without taking some measurements (esp. being able to Un-reverse phase
> the two windings) - it's hard to guess...

I'm glad you are the one working all this out, I would like to see more
information on the construction of the transformer and the disposition
of the windings before speculating too much. If the transformer is of
open frame construction and is not potted, the OP should be able to
easily determine if an E-core is used and if all the windings are on the
center leg?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Randy or Sherry Guttery]

John Byrns wrote:

> Is one or the other really necessarily a "bonus", don't they work in
> opposite directions assuming the two windings are connected in a
> "bucking" configuration?

No - because "bucking" would be dependent on good coupling... Which
happens when the core is NOT saturated - so saturated - not bucking -
bright.

Reactance drops when saturated - so saturated - low reactance - bright.


> Of course we don't actually know they are
> really connected in a "bucking" configuration, we are just speculating
> they are because of the way the schematic is drawn.

I'd be VERY surprised if they are not... 1) why have two windings if
"bucking" (or as I speculated previously -- phase reversal to provide
symmetry) was not needed? 2) why take the extra effort to draw the
schematic that way?

> I'm glad you are the one working all this out, I would like to see more
> information on the construction of the transformer and the disposition
> of the windings before speculating too much. If the transformer is of
> open frame construction and is not potted, the OP should be able to
> easily determine if an E-core is used and if all the windings are on the
> center leg?

Since I don't have "hands on" access - I am left with few options: 1)
guess. 2) offer to see if I can fix the thing. (did I really say that???).

The thing that bothers me about that is if the laminations (assuming
(that dangerous word!) traditional construction) are welded... it might
be extremely tough to get it apart to get at the bobbins... Yes
pictures worth 1K words...

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[John Byrns[_2_]]

In article >,
Randy or Sherry Guttery > wrote:

> John Byrns wrote:
>
> > Is one or the other really necessarily a "bonus", don't they work in
> > opposite directions assuming the two windings are connected in a
> > "bucking" configuration?
>
> No - because "bucking" would be dependent on good coupling... Which
> happens when the core is NOT saturated - so saturated - not bucking -
> bright.

OK, I see we are going in opposite directions on the coupling effect.
If the coupling were perfect when the core is not saturated, then the
light would be as bright as it could get due to the bucking effect of
the two windings. When the transformer becomes saturated decreasing the
coupling, the brightness would have nowhere to go but down due the
residual inductance remaining in the two coils.

So coupling drops when saturated - so saturated - low coupling - dim

This works against the reactance effect you describe below.

> Reactance drops when saturated - so saturated - low reactance - bright.

News Flash, I am really liking the theory I advanced a few messages ago
that the "transformer" is not wound like an ordinary transformer, but
instead has one of the secondaries wound on each outside leg of the
E-core.

The reason I am really liking this theory now is that I looked up the
service data for the General Electric E-155 which has the similar
Colorama tuning system, and the "transformer" is constructed exactly as
I speculated in my earlier message. If the S-W "transformer" is built
the same way then it is a whole new ball game.

> > Of course we don't actually know they are
> > really connected in a "bucking" configuration, we are just speculating
> > they are because of the way the schematic is drawn.
>
> I'd be VERY surprised if they are not... 1) why have two windings if
> "bucking" (or as I speculated previously -- phase reversal to provide
> symmetry) was not needed? 2) why take the extra effort to draw the
> schematic that way?

See above.

> > I'm glad you are the one working all this out, I would like to see more
> > information on the construction of the transformer and the disposition
> > of the windings before speculating too much. If the transformer is of
> > open frame construction and is not potted, the OP should be able to
> > easily determine if an E-core is used and if all the windings are on the
> > center leg?
>
> Since I don't have "hands on" access - I am left with few options: 1)
> guess. 2) offer to see if I can fix the thing. (did I really say that???).
>
> The thing that bothers me about that is if the laminations (assuming
> (that dangerous word!) traditional construction) are welded... it might
> be extremely tough to get it apart to get at the bobbins... Yes
> pictures worth 1K words...

I have seen several posts in rec.antiques.radio+phono over the years
from people who have rewound the GE "transformers", although I don't
remember who they were from.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Alan Douglas]

Hi,
John wrote:

>I have seen several posts in rec.antiques.radio+phono over the years
>from people who have rewound the GE "transformers", although I don't
>remember who they were from.

I made some functional equivalents, using modern Arnold tape-wound
cores. Photos, and probably some explanation, were posted on the
Forum at antiqueradios.com, but I can't easily locate them now. It
was several years ago. I still have some of the cores, if I can find
them.

Alan

[Ken]

John Byrns wrote:
> In article >,
> Randy or Sherry Guttery > wrote:
>
>> John Byrns wrote:
>>
>>> Is one or the other really necessarily a "bonus", don't they work in
>>> opposite directions assuming the two windings are connected in a
>>> "bucking" configuration?
>> No - because "bucking" would be dependent on good coupling... Which
>> happens when the core is NOT saturated - so saturated - not bucking -
>> bright.
>
> OK, I see we are going in opposite directions on the coupling effect.
> If the coupling were perfect when the core is not saturated, then the
> light would be as bright as it could get due to the bucking effect of
> the two windings. When the transformer becomes saturated decreasing the
> coupling, the brightness would have nowhere to go but down due the
> residual inductance remaining in the two coils.
>
> So coupling drops when saturated - so saturated - low coupling - dim
>
> This works against the reactance effect you describe below.
>
>> Reactance drops when saturated - so saturated - low reactance - bright.
>
> News Flash, I am really liking the theory I advanced a few messages ago
> that the "transformer" is not wound like an ordinary transformer, but
> instead has one of the secondaries wound on each outside leg of the
> E-core.
>
> The reason I am really liking this theory now is that I looked up the
> service data for the General Electric E-155 which has the similar
> Colorama tuning system, and the "transformer" is constructed exactly as
> I speculated in my earlier message. If the S-W "transformer" is built
> the same way then it is a whole new ball game.
>
>>> Of course we don't actually know they are
>>> really connected in a "bucking" configuration, we are just speculating
>>> they are because of the way the schematic is drawn.
>> I'd be VERY surprised if they are not... 1) why have two windings if
>> "bucking" (or as I speculated previously -- phase reversal to provide
>> symmetry) was not needed? 2) why take the extra effort to draw the
>> schematic that way?
>
> See above.
>
>>> I'm glad you are the one working all this out, I would like to see more
>>> information on the construction of the transformer and the disposition
>>> of the windings before speculating too much. If the transformer is of
>>> open frame construction and is not potted, the OP should be able to
>>> easily determine if an E-core is used and if all the windings are on the
>>> center leg?
>> Since I don't have "hands on" access - I am left with few options: 1)
>> guess. 2) offer to see if I can fix the thing. (did I really say that???).
>>
>> The thing that bothers me about that is if the laminations (assuming
>> (that dangerous word!) traditional construction) are welded... it might
>> be extremely tough to get it apart to get at the bobbins... Yes
>> pictures worth 1K words...
>
> I have seen several posts in rec.antiques.radio+phono over the years
> from people who have rewound the GE "transformers", although I don't
> remember who they were from.
>
>
> Regards,
>
> John Byrns
>
Byrns wrote: OK, I see we are going in opposite directions on the
coupling effect.
If the coupling were perfect when the core is not saturated, then the
light would be as bright as it could get due to the bucking effect of
the two windings.

NO. If the coupling were perfect, the light would be dim because the two
windings are bucking their max., preventing current flow to the lamp. Ken

[John Goller, k9uwa]

In article >,
says...
>
>

Hi John ... well you found him ... actually a friend of mine had them
wound ... for his E-155 and my E-155 and a few spare parts ... and yes
my buddy Kim Herron has a couple cores rewound that are left... he had
the transformer company in Grand Rapids, Michigan rewind them for us..

and yes its a 3 winding arrangement... nothing like a normal transformer..
so do you have your iron core?

John k9uwa


>I have seen several posts in rec.antiques.radio+phono over the years
>from people who have rewound the GE "transformers", although I don't
>remember who they were from.
>John Byrns

[Randy or Sherry Guttery]

John Byrns wrote:

> OK, I see we are going in opposite directions on the coupling effect.
> If the coupling were perfect when the core is not saturated, then the
> light would be as bright as it could get due to the bucking effect of
> the two windings.

Right - up to the "as it could get" with the core NOT saturated - then
the coupling is good - the windings buck - bulb dim.


> When the transformer becomes saturated decreasing the
> coupling, the brightness would have nowhere to go but down due the
> residual inductance remaining in the two coils.

This is where you go off track - when the core saturates two things
happen - the inductance of the coils drops through the floor - less
inductance - higher current. The coupling also starts to fail as well -
so the bucking effect also decreases - bulb brighter...


> News Flash, I am really liking the theory I advanced a few messages ago
> that the "transformer" is not wound like an ordinary transformer, but
> instead has one of the secondaries wound on each outside leg of the
> E-core.

Not news - this would be common for a saturable reactor.

> The reason I am really liking this theory now is that I looked up the
> service data for the General Electric E-155 which has the similar
> Colorama tuning system, and the "transformer" is constructed exactly as
> I speculated in my earlier message. If the S-W "transformer" is built
> the same way then it is a whole new ball game.

Why? If in fact (as I've postulated most recently) that reactance is
indeed the greater control factor - then whether one coil of the two is
reversed or not would only effect the linearity of the control, not that
it works. I looked up a few site - and found a couple interesting ones...

http://www.allaboutcircuits.com/vol_2/chpt_9/7.html

Down towards the bottom of the page - just above the Scott-T. Notice
that in the final example - they reverse one of the two control windings
- the same thing would be accomplished by leaving the control windings
in phase and reversing the the load winding... Here they use two
reactors to accomplish symmetry - here is a way to do it with one:

http://www.tpub.com/content/neets/14180/css/14180_137.htm
note that this is the first of several pages - you'll have to page
through them to get to the main point. Notice that by the time they get
to the three legged configuration - (and torrids) - the load windings
are opposed to provide symmetry.

Again not knowing the construction of the S/W transformer leaves some
guessing - but as I noted before - if all three windings are wound on a
C form - then bucking may be a significant part of the control
equation - if three legged on an E core (I doubt torrids were in use
back then) - then bucking would not be significant (as that coupling
would be minor compared to the reactance change).

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Randy or Sherry Guttery]

Randy or Sherry Guttery wrote:

a bunch of stuff...

Let me add a point... when I originally looked at the schematic - the
saturable reactor was drawn as a transformer - though it didn't take
long to figure out that it had to be a form of saturable reactor rather
than a transformer... (being an early schematic, I doubt the "standard"
for indicating saturable reactors had been established, and certainly
not yet in common use).

That only leaves figuring out whether the S/W is a two or three legged
configuration (are the two load windings on the same leg). As noted - a
picture might tell a lot. Also - note that the GE version is a fully
buffered (isolated) and driven system - while the S/W's system is part
of the RF / IF B+... the differences make a significant impact on how
the two circuits act (and interact)...

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[John Byrns[_2_]]

In article <3Njai.154612$_c5.5197@attbi_s22>,
(John Goller, k9uwa) wrote:

> In article >,
> says...
>
> Hi John ... well you found him ... actually a friend of mine had them
> wound ... for his E-155 and my E-155 and a few spare parts ... and yes
> my buddy Kim Herron has a couple cores rewound that are left... he had
> the transformer company in Grand Rapids, Michigan rewind them for us..
>
> and yes its a 3 winding arrangement... nothing like a normal transformer..
> so do you have your iron core?

Hi John,

It's not my radio, Randy and I were simply discussing over on
alt.binaries.pictures.radio how the "Stewart-Warner reactance dimmer"
might actually work. This discussion is the result of a post by "Dave
Burson" on alt.binaries.pictures.radio who has a S-W model R-1822 with
an open primary on the reactance control "transformer". I cross posted
the discussion here because I remembered that someone here had talked
about fixing a similar problem on a GE set before. Dave hasn't
responded yet with any information on the physical construction of the
S-W "transformer", whether it's construction is similar to the GE
"transformer" or is different.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

In article >, Ken >
wrote:

> John Byrns wrote:
> > In article >,
> > Randy or Sherry Guttery > wrote:
> >
> >> John Byrns wrote:
> >>
> >>> Is one or the other really necessarily a "bonus", don't they work in
> >>> opposite directions assuming the two windings are connected in a
> >>> "bucking" configuration?
> >> No - because "bucking" would be dependent on good coupling... Which
> >> happens when the core is NOT saturated - so saturated - not bucking -
> >> bright.
> >
> > OK, I see we are going in opposite directions on the coupling effect.
> > If the coupling were perfect when the core is not saturated, then the
> > light would be as bright as it could get due to the bucking effect of
> > the two windings. When the transformer becomes saturated decreasing the
> > coupling, the brightness would have nowhere to go but down due the
> > residual inductance remaining in the two coils.
> >
> > So coupling drops when saturated - so saturated - low coupling - dim
> >
> > This works against the reactance effect you describe below.
> >
> >> Reactance drops when saturated - so saturated - low reactance - bright.
> >
> > News Flash, I am really liking the theory I advanced a few messages ago
> > that the "transformer" is not wound like an ordinary transformer, but
> > instead has one of the secondaries wound on each outside leg of the
> > E-core.
> >
> > The reason I am really liking this theory now is that I looked up the
> > service data for the General Electric E-155 which has the similar
> > Colorama tuning system, and the "transformer" is constructed exactly as
> > I speculated in my earlier message. If the S-W "transformer" is built
> > the same way then it is a whole new ball game.
> >
> >>> Of course we don't actually know they are
> >>> really connected in a "bucking" configuration, we are just speculating
> >>> they are because of the way the schematic is drawn.
> >> I'd be VERY surprised if they are not... 1) why have two windings if
> >> "bucking" (or as I speculated previously -- phase reversal to provide
> >> symmetry) was not needed? 2) why take the extra effort to draw the
> >> schematic that way?
> >
> > See above.
> >
> >>> I'm glad you are the one working all this out, I would like to see more
> >>> information on the construction of the transformer and the disposition
> >>> of the windings before speculating too much. If the transformer is of
> >>> open frame construction and is not potted, the OP should be able to
> >>> easily determine if an E-core is used and if all the windings are on the
> >>> center leg?
> >> Since I don't have "hands on" access - I am left with few options: 1)
> >> guess. 2) offer to see if I can fix the thing. (did I really say that???).
> >>
> >> The thing that bothers me about that is if the laminations (assuming
> >> (that dangerous word!) traditional construction) are welded... it might
> >> be extremely tough to get it apart to get at the bobbins... Yes
> >> pictures worth 1K words...
> >
> > I have seen several posts in rec.antiques.radio+phono over the years
> > from people who have rewound the GE "transformers", although I don't
> > remember who they were from.
> >
> >
> > Regards,
> >
> > John Byrns
> >
> Byrns wrote: OK, I see we are going in opposite directions on the
> coupling effect.
> If the coupling were perfect when the core is not saturated, then the
> light would be as bright as it could get due to the bucking effect of
> the two windings.
>
> NO. If the coupling were perfect, the light would be dim because the two
> windings are bucking their max., preventing current flow to the lamp. Ken

NO, assuming there is no saturation in the core and the coupling is
perfect the reactance of the two windings connected to "buck" would be
very low and the light would be bright, if they are connected to aid
then the total reactance would be four times the reactance of a single
winding and the light would be dim. When we are talking about "perfect"
coupling we are simply talking about a choke with two windings and
considering what the reactance the two series connected windings would
be with the two possible phasing connections.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Randy or Sherry Guttery]

John Byrns wrote:

> NO, assuming there is no saturation in the core and the coupling is
> perfect the reactance of the two windings connected to "buck" would be
> very low and the light would be bright, if they are connected to aid
> then the total reactance would be four times the reactance of a single
> winding and the light would be dim. When we are talking about "perfect"
> coupling we are simply talking about a choke with two windings and
> considering what the reactance the two series connected windings would
> be with the two possible phasing connections.

Now you've lost me - if there is no saturation - then reactance is max -
regardless of "phasing"... particularly in a three-legged config. (where
coupling is insignificant). The only effect phasing would have would be
symmetrical control - and particularly with an E config. cancellation of
the induced AC field before it combines with (to aid or buck) the
control field.

What am I missing?????

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Dave Burson]

John,

I did post another wiring illustration from the schematic page on the
binaries. Please have a look and see whether it clarifies anything. I will
post a photo of the x-former in place, though I doubt it's of much help.
Thanks.

Dave

"John Byrns" > wrote in message
...
> In article <3Njai.154612$_c5.5197@attbi_s22>,
> (John Goller, k9uwa) wrote:
>
>> In article >,
>> says...
>>
>> Hi John ... well you found him ... actually a friend of mine had them
>> wound ... for his E-155 and my E-155 and a few spare parts ... and yes
>> my buddy Kim Herron has a couple cores rewound that are left... he had
>> the transformer company in Grand Rapids, Michigan rewind them for us..
>>
>> and yes its a 3 winding arrangement... nothing like a normal
>> transformer..
>> so do you have your iron core?
>
> Hi John,
>
> It's not my radio, Randy and I were simply discussing over on
> alt.binaries.pictures.radio how the "Stewart-Warner reactance dimmer"
> might actually work. This discussion is the result of a post by "Dave
> Burson" on alt.binaries.pictures.radio who has a S-W model R-1822 with
> an open primary on the reactance control "transformer". I cross posted
> the discussion here because I remembered that someone here had talked
> about fixing a similar problem on a GE set before. Dave hasn't
> responded yet with any information on the physical construction of the
> S-W "transformer", whether it's construction is similar to the GE
> "transformer" or is different.
>
>
> Regards,
>
> John Byrns
>
> --
> Surf my web pages at, http://fmamradios.com/

[Dave Burson]

Here is a photo and a repost of the connection diagram. Note the unused
center terminal at the top and at the bottom. Primariy connections are at
top an can be seen in the photo.

> I'm glad you are the one working all this out, I would like to see more
> information on the construction of the transformer and the disposition
> of the windings before speculating too much. If the transformer is of
> open frame construction and is not potted, the OP should be able to
> easily determine if an E-core is used and if all the windings are on the
> center leg?
>
>
> Regards,
>
> John Byrns
>
> --
> Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

Hi Dave,

Thanks for posting the photo, it makes clear that all three windings are
on the center leg of an E-core unlike the General Electric circuit. It
doesn't make it clear if the two "secondary" windings are connected in a
"bucking" configuration as the schematic implies, or in an "aiding"
configuration. With the open primary what is the voltage across the
light, is it the full heater supply voltage, approximately 6.3 volts, or
is it noticeably lower? This information would help explain how the two
windings are connected and how the circuit works.


Regards,

John Byrns


In article >,
"Dave Burson" > wrote:

> John,
>
> I did post another wiring illustration from the schematic page on the
> binaries. Please have a look and see whether it clarifies anything. I will
> post a photo of the x-former in place, though I doubt it's of much help.
> Thanks.
>
> Dave
>
> "John Byrns" > wrote in message
> ...
> > In article <3Njai.154612$_c5.5197@attbi_s22>,
> > (John Goller, k9uwa) wrote:
> >
> >> In article >,
> >> says...
> >>
> >> Hi John ... well you found him ... actually a friend of mine had them
> >> wound ... for his E-155 and my E-155 and a few spare parts ... and yes
> >> my buddy Kim Herron has a couple cores rewound that are left... he had
> >> the transformer company in Grand Rapids, Michigan rewind them for us..
> >>
> >> and yes its a 3 winding arrangement... nothing like a normal
> >> transformer..
> >> so do you have your iron core?
> >
> > Hi John,
> >
> > It's not my radio, Randy and I were simply discussing over on
> > alt.binaries.pictures.radio how the "Stewart-Warner reactance dimmer"
> > might actually work. This discussion is the result of a post by "Dave
> > Burson" on alt.binaries.pictures.radio who has a S-W model R-1822 with
> > an open primary on the reactance control "transformer". I cross posted
> > the discussion here because I remembered that someone here had talked
> > about fixing a similar problem on a GE set before. Dave hasn't
> > responded yet with any information on the physical construction of the
> > S-W "transformer", whether it's construction is similar to the GE
> > "transformer" or is different.
> >
> >
> > Regards,
> >
> > John Byrns
> >
> > --
> > Surf my web pages at, http://fmamradios.com/

--
Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

In article >,
Randy or Sherry Guttery > wrote:

> John Byrns wrote:
>
> > NO, assuming there is no saturation in the core and the coupling is
> > perfect the reactance of the two windings connected to "buck" would be
> > very low and the light would be bright, if they are connected to aid
> > then the total reactance would be four times the reactance of a single
> > winding and the light would be dim. When we are talking about "perfect"
> > coupling we are simply talking about a choke with two windings and
> > considering what the reactance the two series connected windings would
> > be with the two possible phasing connections.
>
> Now you've lost me - if there is no saturation - then reactance is max -
> regardless of "phasing"... particularly in a three-legged config. (where
> coupling is insignificant). The only effect phasing would have would be
> symmetrical control - and particularly with an E config. cancellation of
> the induced AC field before it combines with (to aid or buck) the
> control field.
>
> What am I missing?????

Notice I said "When we are talking about 'perfect' coupling we are
simply talking about a choke with two windings and considering what the
reactance the two series connected windings would be with the two
possible phasing connections." The "perfect" coupling in this example
implies that all three windings are are on the center leg of the core,
and with the primary disconnected we have a simple choke with two equal
windings. Assuming the choke is perfect, the inductance is zero when
the two coils are connected in the series "bucking" configuration, and
is four times the inductance of one winding when they are connected in
series aiding. You can prove this by either measuring a two winding
choke, or by writing the loop voltage equations for both configurations.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

In article >,
Randy or Sherry Guttery > wrote:

> John Byrns wrote:
>
> > OK, I see we are going in opposite directions on the coupling effect.
> > If the coupling were perfect when the core is not saturated, then the
> > light would be as bright as it could get due to the bucking effect of
> > the two windings.
>
> Right - up to the "as it could get" with the core NOT saturated - then
> the coupling is good - the windings buck - bulb dim.

Either we don't mean the same thing by "buck", or we will each have to
go our own way.

> > When the transformer becomes saturated decreasing the
> > coupling, the brightness would have nowhere to go but down due the
> > residual inductance remaining in the two coils.
>
> This is where you go off track - when the core saturates two things
> happen - the inductance of the coils drops through the floor - less
> inductance - higher current. The coupling also starts to fail as well -
> so the bucking effect also decreases - bulb brighter...

This is where your logic goes wrong, in our perfect idealized
"transformer" with the secondaries connected in the "bucking"
configuration, and no DC in the primary, the inductance is already as
low as it can get, how can the inductance be less than zero when the
"transformer" is saturated?

> > News Flash, I am really liking the theory I advanced a few messages ago
> > that the "transformer" is not wound like an ordinary transformer, but
> > instead has one of the secondaries wound on each outside leg of the
> > E-core.
>
> Not news - this would be common for a saturable reactor.

And not the case anyway as Dave has now posted a picture of his
"transformer" and all three windings appear to be wound on the center
leg.

> > The reason I am really liking this theory now is that I looked up the
> > service data for the General Electric E-155 which has the similar
> > Colorama tuning system, and the "transformer" is constructed exactly as
> > I speculated in my earlier message. If the S-W "transformer" is built
> > the same way then it is a whole new ball game.
>
> Why? If in fact (as I've postulated most recently) that reactance is
> indeed the greater control factor - then whether one coil of the two is
> reversed or not would only effect the linearity of the control, not that
> it works.

My belief all along is that the reactance is the control factor, that is
obvious, there is no other way for it to work. The question is how the
windings are actually connected, if they are connected series aiding
then I can understand how it works. If they are connected so they
"buck" then I don't see how a single leg configuration can work very
well, and the control law would seem to be reversed depending on the
connection, although maybe that's the point.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

In article >,
Randy or Sherry Guttery > wrote:

> Randy or Sherry Guttery wrote:
>
> a bunch of stuff...
>
> Let me add a point... when I originally looked at the schematic - the
> saturable reactor was drawn as a transformer - though it didn't take
> long to figure out that it had to be a form of saturable reactor rather
> than a transformer... (being an early schematic, I doubt the "standard"
> for indicating saturable reactors had been established, and certainly
> not yet in common use).
>
> That only leaves figuring out whether the S/W is a two or three legged
> configuration (are the two load windings on the same leg). As noted - a
> picture might tell a lot.

Dave has now posted a picture, it appears to be a three leg core with
all three windings on the central leg.

> Also - note that the GE version is a fully
> buffered (isolated) and driven system - while the S/W's system is part
> of the RF / IF B+... the differences make a significant impact on how
> the two circuits act (and interact)...

I don't see how the "buffer" in the GE circuit makes any difference at
all, S-W simply make the RF and IF tubes do double duty, serving as a
"buffer" in addition to their normal functions. The buffering aspect
seems to work in an identical fashion to the dedicated "buffer" in the
GE radio.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Randy or Sherry Guttery]

John Byrns wrote:

> Notice I said "When we are talking about 'perfect' coupling we are
> simply talking about a choke with two windings and considering what the
> reactance the two series connected windings would be with the two
> possible phasing connections."

OK - I missed the point that you were talking about something other than
a three legged saturable.

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Randy or Sherry Guttery]

John Byrns wrote:

> Hi Dave,
>
> Thanks for posting the photo, it makes clear that all three windings are
> on the center leg of an E-core unlike the General Electric circuit.

I don't know John, there is something sticking out on both the left and
right ends - like there were a very few winding on each of the outer
legs - normally the shell encloses everything - in this one - there is
something definitely sticking out... or at least it looks like it - Dave
- I know it'd probably be a PITA - but is would it be too much to ask to
try and get a side shot (from north or south as this photo is oriented)?

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Randy or Sherry Guttery]

John Byrns wrote:


> I don't see how the "buffer" in the GE circuit makes any difference at
> all, S-W simply make the RF and IF tubes do double duty, serving as a
> "buffer" in addition to their normal functions. The buffering aspect
> seems to work in an identical fashion to the dedicated "buffer" in the
> GE radio.

There is no need for the filter caps on the primary in the GE version -
as the tube eliminates any posibility of ripple from the reactor getting
into the B+ - as is the case with the S/W. Also by using a tube - GE
can independantly control the saturation curve, direction (inverted from
b+, for instance) or by using agc directly, etc., etc. Lots of
variables introduced by using that buffer tube.

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[Randy or Sherry Guttery]

John Byrns wrote:

> This is where your logic goes wrong, in our perfect idealized
> "transformer" with the secondaries connected in the "bucking"
> configuration, and no DC in the primary, the inductance is already as
> low as it can get, how can the inductance be less than zero when the
> "transformer" is saturated?

Not talking transformer - but rather saturable reactor. Drawn similar -
but windings, core, etc. are different - and they don't interact the
same as a transformer. and I still think that's what's in the S/W. I
think if we get a side shot of the construction - we'll see three
leggs... maybe not.

Bucking - when talking about saturable reactors - bucking means one
winding reversed so that it's induced field is opposite the other
winding's field *when they meet at the control winding*. That would
translate to aiding as looking at the two load windings (but since
they're usually in a three legged config - the two don't interact as
such)... So yes - *one* of us has to "adjust" our perspective....

Again - look at the illustration at the bottom of this page::::

http://www.tpub.com/content/neets/14180/css/14180_138.htm

See the "buck" at the control winding - Note that this is "aid" at the
other load winding? Just the perspective it's viewed from, John.

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[John Byrns[_2_]]

In article <Agnai.22480$dy1.6263@bigfe9>,
Randy or Sherry Guttery > wrote:

> John Byrns wrote:
>
> > Hi Dave,
> >
> > Thanks for posting the photo, it makes clear that all three windings are
> > on the center leg of an E-core unlike the General Electric circuit.
>
> I don't know John, there is something sticking out on both the left and
> right ends - like there were a very few winding on each of the outer
> legs - normally the shell encloses everything - in this one - there is
> something definitely sticking out... or at least it looks like it - Dave
> - I know it'd probably be a PITA - but is would it be too much to ask to
> try and get a side shot (from north or south as this photo is oriented)?

I think you are correct, looking closer at the photo I see what looks
like it may be the side windings.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

In article <Rknai.22481$dy1.19814@bigfe9>,
Randy or Sherry Guttery > wrote:

> John Byrns wrote:
>
>
> > I don't see how the "buffer" in the GE circuit makes any difference at
> > all, S-W simply make the RF and IF tubes do double duty, serving as a
> > "buffer" in addition to their normal functions. The buffering aspect
> > seems to work in an identical fashion to the dedicated "buffer" in the
> > GE radio.
>
> There is no need for the filter caps on the primary in the GE version -
> as the tube eliminates any posibility of ripple from the reactor getting
> into the B+ - as is the case with the S/W. Also by using a tube - GE
> can independantly control the saturation curve, direction (inverted from
> b+, for instance) or by using agc directly, etc., etc. Lots of
> variables introduced by using that buffer tube.

I don't see how any of that makes any difference in the basic operation
of the circuit, S-W simply got a little more work out of their tubes.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

In article <wBnai.22483$dy1.20886@bigfe9>,
Randy or Sherry Guttery > wrote:

> John Byrns wrote:
>
> > This is where your logic goes wrong, in our perfect idealized
> > "transformer" with the secondaries connected in the "bucking"
> > configuration, and no DC in the primary, the inductance is already as
> > low as it can get, how can the inductance be less than zero when the
> > "transformer" is saturated?
>
> Not talking transformer - but rather saturable reactor. Drawn similar -
> but windings, core, etc. are different - and they don't interact the
> same as a transformer. and I still think that's what's in the S/W. I
> think if we get a side shot of the construction - we'll see three
> leggs... maybe not.
>
> Bucking - when talking about saturable reactors - bucking means one
> winding reversed so that it's induced field is opposite the other
> winding's field *when they meet at the control winding*. That would
> translate to aiding as looking at the two load windings (but since
> they're usually in a three legged config - the two don't interact as
> such)... So yes - *one* of us has to "adjust" our perspective....

That's not clear to me, I thought we were talking about all coils being
on the center leg, in which case what I said about "bucking" goes. I
thought I was the one that introduced the windings on three legs idea,
and I had the impression, perhaps wrongly, that you were resisting the
idea. At any rate in the three legged configuration I considered
"bucking" to work exactly as you are describing and simply didn't
realize you were talking about that configuration, so if I have it all
straight who's on first it appears neither of us have to adjust our
perspective.

And I am glad you caught the two outer leg windings on Dave's
transformer that I missed, with that input it all makes sense now.

> Again - look at the illustration at the bottom of this page::::

Sorry I haven't had a chance to look at the links you posted yet.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Dave Burson]

The only PITA is that I've left the chassis at the house of a friend who has
a signal generator (and who knows how to use it). I'll try to get over
there tomorrow. If I can't get a meaningful photo, I can at least sketch
the details. Thanks for the continued interest.

Dave


"Randy or Sherry Guttery" > wrote in message
news:Agnai.22480$dy1.6263@bigfe9...
> John Byrns wrote:
>
>> Hi Dave,
>>
>> Thanks for posting the photo, it makes clear that all three windings are
>> on the center leg of an E-core unlike the General Electric circuit.
>
> I don't know John, there is something sticking out on both the left and
> right ends - like there were a very few winding on each of the outer
> legs - normally the shell encloses everything - in this one - there is
> something definitely sticking out... or at least it looks like it - Dave -
> I know it'd probably be a PITA - but is would it be too much to ask to try
> and get a side shot (from north or south as this photo is oriented)?
>
> best regards...
> --
> randy guttery
>
> A Tender Tale - a page dedicated to those Ships and Crews
> so vital to the United States Silent Service:
> http://tendertale.com

[John Byrns[_2_]]

Hi Dave,

The photo just helps explain how it works, you still have the problem of
fixing the open primary of the "transformer". To fix it you will need
to either have the primary rewound if the break is inside the winding,
or if you are lucky the wire may simply be broken where it attaches to
one of the terminal lugs and you may be able to reattach it.


Regards,

John Byrns


In article >,
"Dave Burson" > wrote:

> The only PITA is that I've left the chassis at the house of a friend who has
> a signal generator (and who knows how to use it). I'll try to get over
> there tomorrow. If I can't get a meaningful photo, I can at least sketch
> the details. Thanks for the continued interest.
>
> Dave
>
>
> "Randy or Sherry Guttery" > wrote in message
> news:Agnai.22480$dy1.6263@bigfe9...
> > John Byrns wrote:
> >
> >> Hi Dave,
> >>
> >> Thanks for posting the photo, it makes clear that all three windings are
> >> on the center leg of an E-core unlike the General Electric circuit.
> >
> > I don't know John, there is something sticking out on both the left and
> > right ends - like there were a very few winding on each of the outer
> > legs - normally the shell encloses everything - in this one - there is
> > something definitely sticking out... or at least it looks like it - Dave -
> > I know it'd probably be a PITA - but is would it be too much to ask to try
> > and get a side shot (from north or south as this photo is oriented)?
> >
> > best regards...
> > --
> > randy guttery
> >
> > A Tender Tale - a page dedicated to those Ships and Crews
> > so vital to the United States Silent Service:
> > http://tendertale.com

--
Surf my web pages at, http://fmamradios.com/

[BFoelsch]

"John Byrns" > wrote in message
...
> In article >,
> Randy or Sherry Guttery > wrote:
>
> > Ken wrote:
> >
> > > So, what is the design method for a transformer that saturates easily?
> >
> > Without getting into a bunch of formulae, etc. (which I'd probably screw
> > up anyway)... a couple of factors - 1) absolute minimum core to couple
> > the windings - i.e. magnetically "starved". 2) no gaps in the core - let
> > the DC current's field circulate well - such that it "interferes" with
> > the AC field. The core can only hold so much flux - if DC is "pushing"
> > the field one way -- the AC (when it opposes) is only going to "reduce"
> > it - not reverse it - (or not fully reverse it) so that the coupling
> > becomes very inefficient. If you look at most output transformers
> > designed for single-ended use - they have a gap in the core somewhere.
> > Obviously - such a gap would not be appropriate for a saturable reactor.
> >
> > And that sets me pondering again whether the primary "effect" is bucking
> > or just reactance... Let's say for the moment that bucking is not the
> > primary mode - and reactance is. Then why the reversed phasing (if
> > bucking isn't a factor)?
> >
> > Well - as I just noted - in a true saturable reactor - the DC flux
> > "overwhelms" the AC flux. Since the AC and DC are additive half the
> > time - and subtractive half the time - the control isn't going to be
> > symmetrical. This is overcome in "the real world" by twin reactors -
> > with the DC "reversed" through one (compared to the other). This way
> > the "offset" in one reactor is "countered" by the other --- and then
> > they "switch roles" when the AC reverses polarity. If you look at the
> > circuit here - (and again - for discussion sake totally ignore bucking)
> > - the AC is "reversed" all the time at one end - or the other of the
> > primary -- as the two coils are phase reversed.
> >
> > Back to saturable reactor theory - when the DC control winding drives
> > the core into saturation - the reactance in the AC winding drops
> > dramatically. That being the case with this circuit - then the two
> > windings would 1) loose coupling so bucking is no longer a factor - and
> > 2) have virtually no reactance in series with the bulb. Then by 1/2 the
> > AC "reactance winding" reversed - both halves would contribute their
> > part to the overall source impedance - providing better symmetry.
> >
> > Now I'm not so sure that pure reactance doesn't play a larger role than
> > originally thought... That perhaps control is indeed more reactance -
> > and "bucking" is just a happy "bonus" to the equation...
>
> Is one or the other really necessarily a "bonus", don't they work in
> opposite directions assuming the two windings are connected in a
> "bucking" configuration? Of course we don't actually know they are
> really connected in a "bucking" configuration, we are just speculating
> they are because of the way the schematic is drawn.
>
> > without taking some measurements (esp. being able to Un-reverse phase
> > the two windings) - it's hard to guess...
>
> I'm glad you are the one working all this out, I would like to see more
> information on the construction of the transformer and the disposition
> of the windings before speculating too much. If the transformer is of
> open frame construction and is not potted, the OP should be able to
> easily determine if an E-core is used and if all the windings are on the
> center leg?
>

Aw, c'mon guys, don't you understand push-pull?

I have never seen the specific radio in question, but the general idea is a
three-legged E-core, DC winding on the center, ac windings on the outer
legs. AC windings are "in-phase." A far as the AC is concerned the AC coils
are in (magnetic) series; as far as the DC coil is concerned they are in
(magnetic) parallel, to use the electrical analogy. Because the AC field
from both coils is equal and opposite, the AC signal is not induced into the
DC coil, but the DC field goes ( in opposing directions) through both legs
of the AC circuit, saturating them both as the current increases.

[John Doty]

John Byrns wrote:

> And I am glad you caught the two outer leg windings on Dave's
> transformer that I missed, with that input it all makes sense now.

Note that in this kind of magnetic amplifier, the fluxes from the
reactance windings must cancel through the control winding. The reason
is that the control winding needs a lot of turns to make enough flux to
saturate the core with a small amount of current. On the other hand, the
reactance windings carry a lot of current, so they must have fewer
turns. Consider that this is a recipe for a transformer that puts high
voltage AC on the control winding unless the fluxes cancel there...

--
John Doty, Noqsi Aerospace, Ltd.
http://www.noqsi.com/
--
Specialization is for robots.

[Randy or Sherry Guttery]

John Byrns wrote:

> Sorry I haven't had a chance to look at the links you posted yet.

Those will explain "bucking" with regards to saturated reactors...

As far as "basic" operation - the use of the buffer tube isolates - wait
a minute - didn't I do this once already? Never mind.

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

[John Doty]

Randy or Sherry Guttery wrote:

> As far as "basic" operation - the use of the buffer tube isolates
> ...

.... and that's important sometimes because it's hard to get good enough
balance between the reactance windings to prevent troublesome coupling
of the output voltage into the control winding.

--
John Doty, Noqsi Aerospace, Ltd.
http://www.noqsi.com/
--
Specialization is for robots.

[John Byrns[_2_]]

In article >,
John Doty > wrote:

> John Byrns wrote:
>
> > And I am glad you caught the two outer leg windings on Dave's
> > transformer that I missed, with that input it all makes sense now.
>
> Note that in this kind of magnetic amplifier, the fluxes from the
> reactance windings must cancel through the control winding. The reason
> is that the control winding needs a lot of turns to make enough flux to
> saturate the core with a small amount of current. On the other hand, the
> reactance windings carry a lot of current, so they must have fewer
> turns. Consider that this is a recipe for a transformer that puts high
> voltage AC on the control winding unless the fluxes cancel there...

Yes, I understand that, in my first post on the subject I had proposed
that the S-W control reactor might have the two "secondary" windings
arranged on the two outer legs of the core so that it would operate as
you describe. Somehow I got the mistaken impression that Randy thought
all three windings were on the central leg of the core, which lead to me
thinking that all the windings were on the central leg when I first saw
the photograph, which doesn't clearly show the windings on the outer
legs because of the angle of the view. With the knowledge that the
secondaries are indeed wound on the outer legs, as I had originally
proposed, the mystery of its operation disappears, and Neil has even
provided a possible explanation for the usefulness of having the lamp
dim as the signal gets stronger.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns[_2_]]

In article >,
Randy or Sherry Guttery > wrote:

> John Byrns wrote:
>
> > Sorry I haven't had a chance to look at the links you posted yet.
>
> Those will explain "bucking" with regards to saturated reactors...

No need to bother, I already understand that as I think I stated in a
previous post, that's why I suggested in my first post in this thread
that perhaps the "two "secondaries" were wound on the two outer legs of
the E-core. This whole discussion has been an unfortunate result of my
misunderstanding what physical construction you were taking about,
somehow I got the impression from your first post that you were
describing a reactor where all three windings were on the central leg of
the E-core, when you didn't respond to the suggestion in my first post
that perhaps the "secondaries" were on the outer legs of the core, the
misunderstanding was cemented in my mind. In a later post where I
reported on the GE E-155 circuit I discovered, which did work the way I
speculated, you did respond with "Not news - this would be common for a
saturable reactor." I took that comment as a general comment about
saturable reactors, specifically not applying to the S-W reactor.
Looking at it again I assume this may have been another
misinterpretation on my part and although you didn't explicitly say so
you were actually talking specifically about the S-W reactor there.

I think we are finally on the same page and now that I understand that
you weren't talking about a reactor with all three windings on the
central leg, if I were to go back and read all of your posts in that
light I would probably find that they make perfect sense.

> As far as "basic" operation - the use of the buffer tube isolates - wait
> a minute - didn't I do this once already? Never mind.

Exactly, the use of a separate "buffer" tube is not necessary to the
operation of the circuit, it is merely an elaboration of the circuit,
perhaps to increase the tube count as was popular at the time.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/