sci.electronics.repair@googlegroups.com

Today's topics:

* Help with wiring colors on old headphones - 11 messages, 8 authors
http://groups.google.com/group/sci.electronics.repair/t/f8481990f5c47309?hl=en
* Can a microwave oven have its output imited? - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/956ea2dbdf891e16?hl=en
* another puzzler - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/b80657d8be4c22cd?hl=en
* an improved electrical resistor - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/992c384af74243b1?hl=en

==============================================================================
TOPIC: Help with wiring colors on old headphones
http://groups.google.com/group/sci.electronics.repair/t/f8481990f5c47309?hl=en
==============================================================================

== 1 of 11 ==
Date: Mon, May 16 2011 8:17 pm
From: Rich Grise

Tim Wescott wrote:
> On 05/14/2011 05:31 PM, Phil Allison wrote:
>> "Tim Wescott"
>>
>>> "If the click seems to come from right inside your head - game over".
>>>
>>> What more do you need? Phil's given you a test to see if the phasing is
>>> correct, can you not figure it out, or what to do if the click seems to
>>> come from your right or your left?
>>
>> ** If both ear phones work but are wired out of phase, the AA cell click
>> test produces a sound that seems to be originating outside the head on
>> both sides. Mono speech or music sounds much the same.
>>
>> The effect is far MORE pronounced than with typical stereo speakers in a
>> room.
>>
>> The OP demonstrates his a monumental ignorance of headphones, hi-fi
>> sound, usenet etiquette and common sense.
>
> Only tangentially related, and mostly useless:
>
> Amateur radio folks like building direct conversion receivers (i.e., mix
> down to baseband). They're simple, hence little, and they work pretty
> well. Their biggest problem is that they have no audio image rejection
> at all -- listening with a 7040kHz oscillator, you'll hear a signal at
> 7040.5 just the same as one at 7039.5.
>
That's the _second_ biggest problem - the biggest is that they're an
unlicensed transmitter.

Hope This Helps!
Rich

== 2 of 11 ==
Date: Mon, May 16 2011 8:33 pm
From: "Phil Allison"

"Rich Grise"
> Tim Wescott wrote:
>
>> Amateur radio folks like building direct conversion receivers (i.e., mix
>> down to baseband). They're simple, hence little, and they work pretty
>> well. Their biggest problem is that they have no audio image rejection
>> at all -- listening with a 7040kHz oscillator, you'll hear a signal at
>> 7040.5 just the same as one at 7039.5.
>>
> That's the _second_ biggest problem - the biggest is that they're an
> unlicensed transmitter.

** Giant HUH ??

Ham radio operators are * licensed * uses of the band from 7MHz to 7.3
Hz - aka the 40 metre band.

In an case, spurious emissions from a flea powered local oscillator is not a
transmitter requiring a licence.

Wot a jerkoff.

..... Phil

== 3 of 11 ==
Date: Mon, May 16 2011 8:41 pm
From: "Paul Hovnanian P.E."

Patrick wrote:

> I have some vinatge headphones (Sennheiser HD424) and want to attach a new
> plug.
>
> Which color wires are the positive ones?
>
> The colors in one of the leads are red & blue and in the other lead black
> &
> yellow. (No wire is used as screening - there's just two wires in each
> lead.)

If they are the standard voice coil types, put them in front of a stereo
speaker and drive the amp with a sine wave. The headphone 'speakers' will
act as microphones. Use an oscilloscope on the pairs of leads to determine
phasing.

--
Paul Hovnanian mailto:Paul@Hovnanian.com
------------------------------------------------------------------
Will code for food.

== 4 of 11 ==
Date: Mon, May 16 2011 9:20 pm
From: John KD5YI

On 5/16/2011 10:17 PM, Rich Grise wrote:
> Tim Wescott wrote:
>> On 05/14/2011 05:31 PM, Phil Allison wrote:
>>> "Tim Wescott"
>>>
>>>> "If the click seems to come from right inside your head - game over".
>>>>
>>>> What more do you need? Phil's given you a test to see if the phasing is
>>>> correct, can you not figure it out, or what to do if the click seems to
>>>> come from your right or your left?
>>>
>>> ** If both ear phones work but are wired out of phase, the AA cell click
>>> test produces a sound that seems to be originating outside the head on
>>> both sides. Mono speech or music sounds much the same.
>>>
>>> The effect is far MORE pronounced than with typical stereo speakers in a
>>> room.
>>>
>>> The OP demonstrates his a monumental ignorance of headphones, hi-fi
>>> sound, usenet etiquette and common sense.
>>
>> Only tangentially related, and mostly useless:
>>
>> Amateur radio folks like building direct conversion receivers (i.e., mix
>> down to baseband). They're simple, hence little, and they work pretty
>> well. Their biggest problem is that they have no audio image rejection
>> at all -- listening with a 7040kHz oscillator, you'll hear a signal at
>> 7040.5 just the same as one at 7039.5.
>>
> That's the _second_ biggest problem - the biggest is that they're an
> unlicensed transmitter.
>
> Hope This Helps!
> Rich
>

No, it doesn't help and is misleading, Rich. 7040kHz is an amateur
frequency. So, it is legal for "Amateur radio folks" as Tim indicated.

John

== 5 of 11 ==
Date: Tues, May 17 2011 12:14 am
From: Ian Jackson

In message <iqst24$fk7$1@dont-email.me>, John KD5YI
<sophi.2@invalid.org> writes
>On 5/16/2011 10:17 PM, Rich Grise wrote:
>> Tim Wescott wrote:
>>> On 05/14/2011 05:31 PM, Phil Allison wrote:
>>>> "Tim Wescott"
>>>>
>>>>> "If the click seems to come from right inside your head - game over".
>>>>>
>>>>> What more do you need? Phil's given you a test to see if the phasing is
>>>>> correct, can you not figure it out, or what to do if the click seems to
>>>>> come from your right or your left?
>>>>
>>>> ** If both ear phones work but are wired out of phase, the AA cell click
>>>> test produces a sound that seems to be originating outside the head on
>>>> both sides. Mono speech or music sounds much the same.
>>>>
>>>> The effect is far MORE pronounced than with typical stereo speakers in a
>>>> room.
>>>>
>>>> The OP demonstrates his a monumental ignorance of headphones, hi-fi
>>>> sound, usenet etiquette and common sense.
>>>
>>> Only tangentially related, and mostly useless:
>>>
>>> Amateur radio folks like building direct conversion receivers (i.e., mix
>>> down to baseband). They're simple, hence little, and they work pretty
>>> well. Their biggest problem is that they have no audio image rejection
>>> at all -- listening with a 7040kHz oscillator, you'll hear a signal at
>>> 7040.5 just the same as one at 7039.5.
>>>
>> That's the _second_ biggest problem - the biggest is that they're an
>> unlicensed transmitter.
>>
>> Hope This Helps!
>> Rich
>>
>
>No, it doesn't help and is misleading, Rich. 7040kHz is an amateur
>frequency. So, it is legal for "Amateur radio folks" as Tim indicated.
>
Even licensed radio amateurs don't want the local oscillator of a
direct-conversion receiver to radiated. The design of the receiver
usually ensures that any radiation is negligible.

Many people don't realise that any superheterodyne receiver is
potentially capable of radiating. Just try listening to the same station
on two cheap FM receivers in the same room, and you'll probably see what
I mean.
--
Ian

== 6 of 11 ==
Date: Tues, May 17 2011 12:17 am
From: Ian Jackson

In message <vPadnf8mzLS9c0zQnZ2dnUVZ_uydnZ2d@posted.isomediainc>, Paul
Hovnanian P.E. <paul@hovnanian.com> writes
>Patrick wrote:
>
>> I have some vinatge headphones (Sennheiser HD424) and want to attach a new
>> plug.
>>
>> Which color wires are the positive ones?
>>
>> The colors in one of the leads are red & blue and in the other lead black
>> &
>> yellow. (No wire is used as screening - there's just two wires in each
>> lead.)
>
>If they are the standard voice coil types, put them in front of a stereo
>speaker and drive the amp with a sine wave. The headphone 'speakers' will
>act as microphones. Use an oscilloscope on the pairs of leads to determine
>phasing.
>
Is there going to be a prize for suggesting the most obscure (but
effective) way of determining the phasing?
--
Ian

== 7 of 11 ==
Date: Tues, May 17 2011 2:11 am
From: upsidedown@downunder.com

On Mon, 16 May 2011 11:46:54 +0100, Martin Brown
<|||newspam|||@nezumi.demon.co.uk> wrote:

>On this topic did anyone else see the NHK broadcast a few months back
>about a digital version of binaural recording that alters the phase
>frequency response of the high end of close miked material to extend the
>stereo sound stage vertically. The trick works by tweaking the frequency
>phase relationship to match what the ear expects from a wave incident at
>a given angle. It just sounded odd on loudspeakers.

Was this some kind of dummy head recording or some kind of ambisonics
(Gerzon) WXYZ recording ?

== 8 of 11 ==
Date: Tues, May 17 2011 2:40 am
From: upsidedown@downunder.com

On Sun, 15 May 2011 10:31:35 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

>** If both ear phones work but are wired out of phase, the AA cell click
>test produces a sound that seems to be originating outside the head on both
>sides. Mono speech or music sounds much the same.
>
>The effect is far MORE pronounced than with typical stereo speakers in a
>room.

Puking two speakers with front panels against each other is a quite
easy way to check polarity. If the polarity is correct, you will hear
some low frequency sounds emitted from the combination. If the
polarity is wrong, you will hear only mid- and high pitch sounds,
since the low frequency air is moving between the cones of the
speakers.

With headphones, you either get "in head" or unrealistic sound
depending on the phasing of headphones.

Sennheiser did the wiring correctly by keeping all four wires separate
and connected to a 4 pin DIN plug and by adding a 4 pin DIN to 6.35 mm
plug adaptor.

As a kid, I was really pissed of by the convention of using common
returns in headphones. I was testing frequency diversity reception of
the same broadcast programs on two different shortwave bands with two
receivers. Unfortunately, the other receiver was of AC/DC type with
the full 220 Vac in the chassis. Thus I had to rewire the phones so
that one side could (potentially) siting on 220 Vac, and the other
side sitting close to ground potential.

After this alteration, I had no problems with this arrangement.

No problems, no problems, no problems :-)

== 9 of 11 ==
Date: Tues, May 17 2011 2:41 am
From: "Dave Plowman (News)"

In article <93dstcFeenU1@mid.individual.net>,
Phil Allison <phil_a@tpg.com.au> wrote:

> "David Looser"
> >
> > What *was* being talked about was connecting a mono signal across tip
> > and ring, thus putting the two transducers in series.
> >

> ** This is sometimes deliberately done with the headphone sockets fitted
> to small ( mono) mixing desks and disco mixers.

> It means the internal amplifier, often just an op-amp, sees a load of
> four times the value it would if wired in parallel and that fitting a
> mono plug in the socket does not create a short.

I suppose it's too much to expect an apology for the earlier crap you
wrote - given you are so quick to jump down others throats if they make
one?

--
*If at first you don't succeed, then skydiving definitely isn't for you *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

== 10 of 11 ==
Date: Tues, May 17 2011 2:43 am
From: Martin Brown <|||newspam|||@nezumi.demon.co.uk>

On 17/05/2011 10:11, upsidedown@downunder.com wrote:
> On Mon, 16 May 2011 11:46:54 +0100, Martin Brown
> <|||newspam|||@nezumi.demon.co.uk> wrote:
>
>> On this topic did anyone else see the NHK broadcast a few months back
>> about a digital version of binaural recording that alters the phase
>> frequency response of the high end of close miked material to extend the
>> stereo sound stage vertically. The trick works by tweaking the frequency
>> phase relationship to match what the ear expects from a wave incident at
>> a given angle. It just sounded odd on loudspeakers.
>
> Was this some kind of dummy head recording or some kind of ambisonics
> (Gerzon) WXYZ recording ?

Digital alteration of the phase and amplitude response with frequency
applicable only to sounds with reasonably complex harmonic content.

The demo was a church bell that was made to ring up then down on axis,
left then right as in a ping pong stereo demo and finally at the corners
of a rectangle. It just sounded odd on loudspeakers.

If my memory serves I think they said that sounds coming from above have
slightly more high frequency components and a phase lead. The adjustment
fools the brain into putting the sound where it "belongs".

Regards,
Martin Brown

== 11 of 11 ==
Date: Tues, May 17 2011 3:07 am
From: "Phil Allison"

"Ian Jackson"
>>
> Is there going to be a prize for suggesting the most obscure (but
> effective) way of determining the phasing?

** I got one:

Insert a pin through a hole in the earphone grille and let it rest loosely
the diaphragm.

Use the AA cell test.

One polarity will evict the pin.

.... Phil

==============================================================================
TOPIC: Can a microwave oven have its output imited?
http://groups.google.com/group/sci.electronics.repair/t/956ea2dbdf891e16?hl=en
==============================================================================

== 1 of 2 ==
Date: Mon, May 16 2011 8:24 pm
From: Cydrome Leader

William Sommerwerck <grizzledgeezer@comcast.net> wrote:
> "Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
> news:iqsm5d$ap4$1@reader1.panix.com...
>> William Sommerwerck <grizzledgeezer@comcast.net> wrote:
>
>>> What do you mean by excessive? If a magnetron can be modulated
>>> by varying its B+, why shouldn't each PWM cycle be just one or two
>>> seconds long? You DO NOT want the magnetron running at full power
>>> for "long" periods, followed by even longer periods off (eg, one minute,
>>> four minutes off, for 20%).
>
>> If you like switching a kilowatt sized transformer on and off every
>> second, power to you. Same for a reed relay rated at kV at hundreds
>> of mA.
>> It would obviously be easier with one of those switching power supply
>> microwaves, but that's not how the old microwaves worked.
>
> As far as I know, my 10-year-old GE is a "newer" model.
>
> This has become one of those "inquiring minds want to know" questions. There
> are leakage meters, which would show changes in level. Does anyone make a
> power meter you can place in the cavity?

You might get by with a cup of water and a light bulb. Neon lights with
the leads twisted together was the standard "indicator" for microwaves
when I last touched these things. You really want the cup of water as a
dummy load when putting weird stuff in a microwave.

I just ran at test like that on my made in 1981 samsung microwave. It
surprisingly has a digital clock and numeric keypad- space age stuff for
the time. This thing was clearly made when they were terrified of
microwave leaks. There are a whopping 20 torx screws alone holding the
glass in the front door, plus more holding the door together.

Anyways, in defrost mode, the magnetron is clearly cycled on and off in 15
second intervals. I could tell when it was on from when the small
lightbulb lit up.

== 2 of 2 ==
Date: Mon, May 16 2011 9:14 pm
From: "Michael A. Terrell"

William Sommerwerck wrote:
>
> "Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
> news:iqsm5d$ap4$1@reader1.panix.com...
> > William Sommerwerck <grizzledgeezer@comcast.net> wrote:
>
> >> What do you mean by excessive? If a magnetron can be modulated
> >> by varying its B+, why shouldn't each PWM cycle be just one or two
> >> seconds long? You DO NOT want the magnetron running at full power
> >> for "long" periods, followed by even longer periods off (eg, one minute,
> >> four minutes off, for 20%).
>
> > If you like switching a kilowatt sized transformer on and off every
> > second, power to you. Same for a reed relay rated at kV at hundreds
> > of mA.
> > It would obviously be easier with one of those switching power supply
> > microwaves, but that's not how the old microwaves worked.
>
> As far as I know, my 10-year-old GE is a "newer" model.
>
> This has become one of those "inquiring minds want to know" questions. There
> are leakage meters, which would show changes in level. Does anyone make a
> power meter you can place in the cavity?

Connect a voltmeter across the power line. You will see the voltage
change as the oven switched between a couple Watts to 700-1100 Watts. I
can hear a change in the hum from the HV transformer on my oven.

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

==============================================================================
TOPIC: another puzzler
http://groups.google.com/group/sci.electronics.repair/t/b80657d8be4c22cd?hl=en
==============================================================================

== 1 of 1 ==
Date: Mon, May 16 2011 11:37 pm
From: "Trevor"

"Don Pearce" <spam@spam.com> wrote in message
news:4dd0b4d6.442940877@news.eternal-september.org...
>>(First you MUST assume the coin is untampered with, you cannot assume the
>>same for a TV game show however!)
>
> What has this to do with the question?

Nothing I guess for the specific case in question. As was pointed out there
is only one possible set of events if a switch is offered for a one of 3
game of chance. I admit to confusing this with other TV games where the host
can and does influence the outcome.

Trevor.

==============================================================================
TOPIC: an improved electrical resistor
http://groups.google.com/group/sci.electronics.repair/t/992c384af74243b1?hl=en
==============================================================================

== 1 of 1 ==
Date: Tues, May 17 2011 3:41 am
From: mm

Middle sentence of second paragraph is the most relevant.

Otis Frank Boykin was born in 1920 in Dallas, Texas. His mother was a
homemaker and his father was a carpenter. He worked as a laboratory
assistant at the nearby University's aerospace laboratory. Otis
attended Fisk University and Illinois Institute of Technology, but
dropped out after two years because his parents could not afford his
tuition.

Boykin, in his lifetime, ultimately invented more than 25 electronic
devices. One of his early inventions was an improved electrical
resistor for computers, radios, televisions and an assortment of other
electronic devices. Other notable inventions include a variable
resistor used in guided missiles and small component thick-film
resistors for computers.[2]

---------------

So how can one improve an electrical resistor?

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