Toshiba TV29C90 problem; Image fades to black...

[Andrew Holme]

jackbruce9999@yahoo.com wrote:

2 questions about a fully DC Sine Wave....let's suppose you have a DC
Sine wave which varies from +5V to +15V peak-to-peak going into a load
with R, L, and C components.....

There is no such thing as a "DC sine wave." I suspect you mean what would
more correctly be described as a 10 volt peak-to-peak sine wave with a +10
volt DC offset.

Question #1:
Is the load's impedance a function of R, L, and C (and wave frequency)
or is it simply just R (i.e. Z=R)? In other words does non-resistive
impedance (L + C) really only matter with an AC signal OR anytime
voltage varies periodically (even if it is all DC)?

The principle of superposition applies: the currents and voltages in the
circuit will be the sum of those that would result if the DC voltage and the
AC sine wave were applied to it seperately.

Question #2:
Would a "regular" negative peak detector ciruit, like shown here:


http://www.elektroda.net/cir/index/Detector%20Circuits/NEGATIVE%20PEAK%20DETECTOR.htm


work for the DC Wave described? Will it output +5V or do negative
peak detectors only work for AC signals?

That circuit (I've fixed the link) exploits the fact that the LM139
comparator has an open-collector output. It runs off a negative rail, and
cannot produce a positive output voltage.

 

[NSM]

<jackbruce9999@yahoo.com> wrote in message
news:1118444034.606252.243120@z14g2000cwz.googlegroups.com...

read the original post - talking about a sine wave bouncing between +5V
and +15V - no where near negative

That's an AC wave with a DC offset.

N

 

[Don Bowey]

On 6/10/05 3:13 PM, in article
1118441581.770052.189710@g47g2000cwa.googlegroups.com,
"jackbruce9999@yahoo.com" <jackbruce9999@yahoo.com> wrote:

How come? Do you object to the term "DC" - is monophasic acceptable to
you?

See also:

http://64.233.161.104/search?q=cache:SMA_gSlzQ18J:global.daikin.com/global/our
_product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_en

Your posts have all the characteristics that indicate you are a troll. If
you aren't I suggest you quit being combative and learn from what the
posters are saying.

And re the link; that refers to an inverter that uses a DC input and outputs
a sinewave. You must be troll.

 

[Don Bowey]

On 6/10/05 3:53 PM, in article
1118444034.606252.243120@z14g2000cwz.googlegroups.com,
"jackbruce9999@yahoo.com" <jackbruce9999@yahoo.com> wrote:

read the original post - talking about a sine wave bouncing between +5V
and +15V - no where near negative

So the 10V p-p sinewave is riding on 10VDC. There is no requirement that a
sinewave must have an absolute negative component.

 

[ehsjr]

jackbruce9999@yahoo.com wrote:

2 questions about a fully DC Sine Wave....let's suppose you have a DC
Sine wave which varies from +5V to +15V peak-to-peak going into a load
with R, L, and C components.....

Question #1:
Is the load's impedance a function of R, L, and C (and wave frequency)
or is it simply just R (i.e. Z=R)? In other words does non-resistive
impedance (L + C) really only matter with an AC signal OR anytime
voltage varies periodically (even if it is all DC)?


Question #2:
Would a "regular" negative peak detector ciruit, like shown here:

http://www.elektroda.net/cir/index/Detector%20Circuits/NEGATIVE%20PEAK%20DETECTOR.htmgative


work for the DC Wave described? Will it output +5V or do negative peak
detectors only work for AC signals?

Thank you.

Question 1: A capacitor "capacitates" whether it sees
AC or DC. An inductor "inducts" whether it sees AC or
DC. A resistor resists whether it sees AC or DC. You
might find it beneficial to think of what happens to
each component on a component level rather than thinking
of total impedance. Understand what each component
does, and circuit impedance will make more sense.

Question 2: 404 file not found error
That said, you can peak detect on a varying DC
sine. As someone else said, its AC with a DC offset.

Ed

 

[Bob Monsen]

jackbruce9999@yahoo.com wrote:

2 questions about a fully DC Sine Wave....let's suppose you have a DC
Sine wave which varies from +5V to +15V peak-to-peak going into a load
with R, L, and C components.....

Question #1:
Is the load's impedance a function of R, L, and C (and wave frequency)
or is it simply just R (i.e. Z=R)? In other words does non-resistive
impedance (L + C) really only matter with an AC signal OR anytime
voltage varies periodically (even if it is all DC)?

The impedance of a set of passive devices is independent of the voltage
across them. It only depends on R, L, C, and f. The fact that there is a
DC component makes no difference.

An inductor will pass DC current as if it were a wire. Only differences
in current cause a voltage across it. A capacitor will not pass DC, so
the DC does not matter. Obviously, a resistor is a resistor, and cares
nothing for ac vs dc.

This is only true for ideal components. In the real world, inductors,
caps and resistors have voltage limitatations. They are usually well
beyond 15V, though.

Question #2:
Would a "regular" negative peak detector ciruit, like shown here:

http://www.elektroda.net/cir/index/Detector%20Circuits/NEGATIVE%20PEAK%20DETECTOR.htmgative


work for the DC Wave described? Will it output +5V or do negative peak
detectors only work for AC signals?

Thank you.

Your link has crap on the end. Here it is without the crap:

http://www.elektroda.net/cir/index/Detector%20Circuits/NEGATIVE%20PEAK%20DETECTOR.htm

With this circuit, the input at V+ will always be outside the power
rails. Thus, it will not work.

NOTE: I changed the followup-to field to sci.electronics.basics, because
that is where this thread belongs. I hope you don't mind.

---
Regards,
Bob Monsen

 

[Rich Grise]

On Fri, 10 Jun 2005 14:55:02 -0700, jackbruce9999 wrote:

2 questions about a fully DC Sine Wave..

If you think that the term "fully DC Sine Wave" even means anything,
then you have not understood the coursework. Either your teacher is
incompetent, or you have been spending too much time partying and not
enough time studying.

Good Luck!
Rich

 

[Rich Grise]

On Fri, 10 Jun 2005 16:51:10 -0700, Don Bowey wrote:

On 6/10/05 3:13 PM, in article
1118441581.770052.189710@g47g2000cwa.googlegroups.com,
"jackbruce9999@yahoo.com" <jackbruce9999@yahoo.com> wrote:

How come? Do you object to the term "DC" - is monophasic acceptable to
you?

See also:

http://64.233.161.104/search?q=cache:SMA_gSlzQ18J:global.daikin.com/global/our
_product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_en


Your posts have all the characteristics that indicate you are a troll.

Bullshit. This kid is not a troll, by any means. He's just a student
desperate to weasel answers to his final without having to learn the
material he was supposed to have learned while partying and chasing tail.

A troll is a much more serious matter. This is just a child who needs
to fail the course, have Mom and Dad scold him, and next semester,
pay attention in class.

Cheers!
Rich

 

[John Popelish]

jackbruce9999@yahoo.com wrote:

2 questions about a fully DC Sine Wave....let's suppose you have a DC
Sine wave which varies from +5V to +15V peak-to-peak going into a load
with R, L, and C components.....

Question #1:
Is the load's impedance a function of R, L, and C (and wave frequency)
or is it simply just R (i.e. Z=R)? In other words does non-resistive
impedance (L + C) really only matter with an AC signal OR anytime
voltage varies periodically (even if it is all DC)?


Question #2:
Would a "regular" negative peak detector ciruit, like shown here:

http://www.elektroda.net/cir/index/Detector%20Circuits/NEGATIVE%20PEAK%20DETECTOR.htmgative


work for the DC Wave described? Will it output +5V or do negative peak
detectors only work for AC signals?

Thank you.

According to Fourier analysis, any repeating waveform can be
decomposed into harmonically related and appropriately phase shifted
sine waves and also a DC component. If all the components involved
are linear, then they react to each of these components,
independently, and the result is the linear sum of all those
reactions. So the capacitors react to the DC component as open
circuits, and the inductors as short circuits. At all frequencies,
the resistances follow ohms law, and at each AC harmonic, the
inductances and capacitances react in their normal frequency dependent
ways.

Throw in one nonlinear component, like a diode, and you have to do a
completely different kind of analysis.

 

[Jamie]

marslee@hotmail.com wrote:

I have an old hitach 578EM multi system VCR, manfactured in 1990.
Recently, it eat tapes.
The following is what i see:
When i press play, the tape moves but only the left wheel of the tape,
the right wheel does not move at all. The vcr works fine in fast
reverse and forward.

Anyone have experience with this old machine?

most likely you need a new pinch and idler wheel kit.

 

[nobody]

Make sure there's no slipping rubber belts. Replace them if need be. O-rings
can be substituted for small belts. Also take rubbing alcohol and apply to
all of the rubber surfaces (pinch rollers, idler wheels, etc) to get them
gripping again. This may not work well if they're too worn or dried out.

<marslee@hotmail.com> wrote in message
news:1118450537.908081.271030@g49g2000cwa.googlegroups.com...

Anyone have experience with this old machine?

 

[Fred Bloggs]

Question #2:
Would a "regular" negative peak detector ciruit, like shown here:

http://www.elektroda.net/cir/index/Detector%20Circuits/NEGATIVE%20PEAK%20DETECTOR.htmgative


work for the DC Wave described?

That is not a "regular" peak detector, it is a comparator used as an
overcompensated opamp follower and exploits the open collector output
characteristic of fast discharge and slow ( 10 second) charge of the
capacitor. In concept it will work for a varying "DC sine wave" by
replacing "-Vcc" with "GND" and all "GND"'s with "+15V" in that circuit
diagram only. Then Vout= "Vpk,neg" =+5V.

 

[Don Hickey]

I believe a more likely candidate than the PC would be the monitor. High
voltage for the screen requires some large electrolytic capacacitors. Have
you taken any steps to isolate the failing unit.... PC, monitor, scanner,
external drives, etc?


<danr_18@yahoo.com> wrote in message
news:1118414106.665624.105390@f14g2000cwb.googlegroups.com...

I'm not sure where to post this, so I've searched for old msgs. Please
excuse me if I'm in the wrong place.

I bought an IBM ThinkCentre PC a few months ago (well, now Lenovo
Thinkcentre). Since the beginning, I've been getting a bitter taste in
my mouth and watering/burning in my mouth, when the computer is on (so
I keep ventilation up.. which is not always so easy). I thought maybe
some chemicals need to burn off.. but now I'm getting concerned. I
don't smell anything.

I've called IBM, they had me look for leaking electrolyte from
capacitors on the motherboard. I don't SEE any (does that mean I'm free
in that regard)? They have now escalated and will get back to me.

(My Laser printer is OFF... In case you're wondering about Ozone
effects.)

Any other suggestions?

 

[Art]

"Unit is dead. Fuse F601 blows (black). Excessive AC current flow through
the degaussing coil. A change in the characteristics of D808 can cause
excessive current to flow through the degaussing coil and blow F601. Replace
D808."

Leonard: This is a copy/paste from Panasonic's Web Site. If you check the
new part supplied, maybe even with the same part number, you may find a
difference in type and parameters. Please post your in-depth discoveries
regarding this. Thanks!

"Leonard Caillouet" <no@no.com> wrote in message
news:f%eqe.12799$Hj.6708@lakeread02...

Where do you find it on the Panasonic web site?

The have a notation to replace the thermistor, but I can't find anything
about a different part.

Leonard

"Art" <plotsligt@comcast.net> wrote in message
news:a4Sdna_M-MnJbDXfRVn-pA@comcast.com...
Actually there is a different degauss thermistor that is to be used when
you
encounter the 'fuse failure syndrome in these sets. Also in Thomson and
Phillips sets, it seems the original degauss thermistor allows too much
current draw during the degauss cycle, over time the fuse just gives up.
All
three manufacturers have notations regarding this problem on their
respective web sites, the cures, and part numbers required.
"Rono" <rono@nl.rogers.com> wrote in message
news:gL-dnSg0pKoKBjrfRVn-gg@rogers.com...
I beleive there is a fuse problem with these units, where the degaussing
draws too much curent, just at initial startup. Try a "slightly" higher
fuse,
& I think you may have to replace the thermistor, & check back for more
posts attached to yours, to be sure. Rono.

 

[Tam/WB2TT]

<jackbruce9999@yahoo.com> wrote in message
news:1118443865.353870.184610@o13g2000cwo.googlegroups.com...

There is no such thing as a "DC sine wave." I suspect you mean what
would more
correctly be described as a 10 volt peak-> to-peak sine wave with a +10
volt DC offset.

Not that it's that important, but I don't see why a "DC sine wave" is
an impossible concept, considering the definition of DC as a current
which flows in one direction:

Maybe you shouldn't believe everything you read. DC has:

1. Constant amplitude (that's not to say you can't change it.
2. Frequency of 0 Hz. Also, a non 0 frequency does not imply polarity
changes.

Tam

 

[MG]

"Dave" <nospam@nowhere.com> wrote in message news:42aa130f@212.67.96.135...

Bob Eldred wrote:

Impedance varies with frequency if there are reactive components, L's and
C's.

That is not always true.

Take
1) A resistor of resistance R in series with a capacitor of capacitance C.

2) Another identical resistor of resistance R, but in series with an
inductor L.

Make R=sqrt(L/C)

and put 1 and 2 in parallel and measure the impedance across that
combination. The impedance is always R, and is independent of frequency.

A useless fact I would admit!!

Not exactly useless, you just described a Zobel network.

It is used as crossover to feed two loudspeaker on HI range and LOW range
presenting a constant resistive load to the Amp.

It is used to compensate a shunt at higher freq. The transfer function is
perfectly flat even with two reactances in the circuit.

It is used to terminate a DC distribution line R+L with a R+C to avoid
resonances, the line is perfectly damped, when the load current steps there
are no oscillatory transients.

MG

MG

 

[James Sweet]

<danr_18@yahoo.com> wrote in message
news:1118414106.665624.105390@f14g2000cwb.googlegroups.com...

I'm not sure where to post this, so I've searched for old msgs. Please
excuse me if I'm in the wrong place.

I bought an IBM ThinkCentre PC a few months ago (well, now Lenovo
Thinkcentre). Since the beginning, I've been getting a bitter taste in
my mouth and watering/burning in my mouth, when the computer is on (so
I keep ventilation up.. which is not always so easy). I thought maybe
some chemicals need to burn off.. but now I'm getting concerned. I
don't smell anything.

I've called IBM, they had me look for leaking electrolyte from
capacitors on the motherboard. I don't SEE any (does that mean I'm free
in that regard)? They have now escalated and will get back to me.

(My Laser printer is OFF... In case you're wondering about Ozone
effects.)

Any other suggestions?

Perhaps you have an allergy to a compound used in one of the many plastics,
adhesives, inks, and other substances that go into making or packing the
computer? Is anyone else bothered by it? Things like that can be tricky to
track down but some people are just very sensitive to certain chemicals.

 

[James Sweet]

"Don Bowey" <dbowey@comcast.net> wrote in message
news:BECF757E.5171%dbowey@comcast.net...

On 6/10/05 3:13 PM, in article
1118441581.770052.189710@g47g2000cwa.googlegroups.com,
"jackbruce9999@yahoo.com" <jackbruce9999@yahoo.com> wrote:

How come? Do you object to the term "DC" - is monophasic acceptable to
you?

See also:


http://64.233.161.104/search?q=cache:SMA_gSlzQ18J:global.daikin.com/global/our

_product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_en


Your posts have all the characteristics that indicate you are a troll. If
you aren't I suggest you quit being combative and learn from what the
posters are saying.

And re the link; that refers to an inverter that uses a DC input and
outputs
a sinewave. You must be troll.

He's obviously not a troll, just not super knowledgeable about the subject
at hand. If he were a troll he'd have crossposted to something like
alt.vampires or alt.masturbation and alt.catholosism.

 

[Ban]

jackbruce9999@yahoo.com wrote:

P.S.
I would challenge you to prove that the term "DC sine wave" is
objectionable because it is fundamentally wrong as opposed to being at
odds with conventional terminology and nomenclature.....Isn't a sine
wave that operates as all positive voltages always yielding currents
that operate in only one direction (i.e. "direct current")? Surely
you wouldn't call this AC, would you? Isn't "DC sine wave" a more
concise and readily (albeit only slightly more so) concept that an
"AC sine wave that has been fully DC offset"? Is it conceivable that
conventional terminology and nomenclature could have evolved such that
"DC sine wave" was acceptable? If not, why not? How is it
fundamentally wrong? (as opposed to being at odds with convention)

The signal would be said to have a DC-component (of the average value) and
an AC-component(of the rms value minus the DC)
--
ciao Ban
Bordighera, Italy

 

[R Adsett]

In article <1118461037.539035.305830@z14g2000cwz.googlegroups.com>,
jackbruce9999@yahoo.com says...

Is that definition of "DC" written in stone (i.e. fundametnally true)
or as defined by convention? How is a sine wave operating as all
postive voltages not yielding a current (albeit variable) of a single
polarity, single direction that does not alternate? Isn't saying it is
an "alternating current with a dc offset" a rather queer way of saying
things since there actually is no (net) alternating (i.e.
bi-directional) current flow?
The only difference between your "DC sine wave" and an your "AC sine

wave" is where you happen to choose your reference point. Most of us
don't consider a wavefornm to magically shift from AC to DC simply by a
change of reference.

Robert