For Hire: NYC E.E. Technician

Radio Transmitter. I shoulda known...I imagined a big whopping switch/breaker somewhere.

If I can bother you to answer a dumb question: When an FM station calls itself "100,000 Watts" is that ERP or is that transmitter actually consuming 100+kw off the line? Thanks.

Reply to
C. Upskirts
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Charles; a capacitors retained voltage is much higher than the voltage that it is boosting; like in an air Conditioning Unit, it is a temporary characteristic used for starting only, but if you turn an AC or even an old radio On then Off disconnect the leads and put a vom across it you'l see for yourself.

i hope we're not going to have a piss match over this }: it's a electrolitic fact .

Reply to
Roy Q.T.

I figured that much from the experience.

the internal switch gear of the unit performs the job of discharging the caps? right? like when you pull a cap off an active circuit and shunt the terminals to discharge it before testing.

I don't know where Charles got his theory from but the supply voltage is one thing the stored energy in an In Line Capacitor (Electrolitic Types) multiplies by two-three times the Line Load.

are you two related? }:-)

I remember showing this to an incredulous friend of mine: I carefully pulled a cap off an old radio right off the line current and put my VOM on it to show him the 500VDC., he was shocked and was glad i had studied E.E. Physics, since he had studied Marine Biology and was unaware of he Capacity of a Capacitor., of course it discharges quite quickly, but we plugged it in again an Wham 500VDC from a Cap on 110VAC. same thing with the AC I shunted with my arms :-o

oh! the radio was working fine....

Reply to
Roy Q.T.

the method varies. the most common is a fixed resistor accross the cap, sized to take the voltage to below safe levels in a few seconds.

the stored energy of a capacitor is dependent on the size of the capacitor (in uF) and the applied voltage.

the stored voltage in a capacitor will equal the applied voltage minus internal leakage. as time progresses the voltage becomes zero. there are a couple of rare exceptions to this.

the phrase "line load" is incorrect usage in this context. i believe you meant "line voltage"

could be but not that i know of

110 VAC, when rectified (full wave) will be 110 * sqrt2 * 2 = 311 volts (minus voltage drop of any rectifier devices) when rectified half wave it is 110 * sqrt 2 - 155 Vdc

if i understand the description of your experiment correctly the voltage on the capacitor could be anything between plus or minus 155 volts depending on the instantaneous value of the line voltage at the instant the circuit was broken.

its possible if you were using an analog voltmeter the movement was overshooting.

i would not attempt to duplicate this experiment if the capacitor in question is a normal (polarized) electrolytic. they tend to get angry when reverse voltage is applied.

Reply to
TimPerry

correction here: i meant full wave bridge rectified

Reply to
TimPerry

When doing the math i figured the same as you about 377vdc but it goes higher in real life i can't recall the =B5Farads of that cap but perhaps if you throw in Q from Faradays Equation & some other factors from up your sleeve, you would figure out how 500vdc got on the meter without assuming technical error on my behalf.

I always calibrated my D'Arsonval meter on every different test., depending if i was measuring resistnce, voltgage or current.

maybe the cap was defective, then, there were transistors involved and could be the VA on the Cap was higher than the Line Voltage.

Theory may get us close to the Truth or in this case, Apparent Voltage, Technical Reality does not conform to Life nor to mortal creations.We can only come close with Theory, to be right on, it must be measured and tested under every given & obscure condition possible.

I knew you wouldn't accept it., but there it was 500dvc whether we like it or not.

30Kv rectifiers on that Kavorkian + 20%, plus unknown factors, the Charge Q on that Radio Station Secondary Circuitry maybe much higher than calculated the conventional way, under differing conditions such as power on & normal usage Vs everything On minus - The Load., nevertheless, approximate danger is danger enough to handle carefully. I don't envy your position };-)
Reply to
Roy Q.T.

I woudn't reverse the polarity, (It could damage the cap) but, just shunting the terminals on the capacitor to each other alone produce a nifty spark.

Reply to
Roy Q.T.

higher in real life i can't recall the µFarads of that cap but perhaps if you throw in Q from Faradays Equation & some other factors from up your sleeve, you would figure out how 500vdc got on the meter without assuming technical error on my behalf.

i assume an error in procedure and/or discription and/or meter calibration

depending if i was measuring resistnce, voltgage or current.

a high impedance VTVM or DVM or ocilliscope would be more appropriate for this measurement

could be the VA on the Cap was higher than the Line Voltage.

what transistors? you said you simply applied a capacitor to the AC line

Technical Reality does not conform to Life nor to mortal creations.We can only come close with Theory, to be right on, it must be measured and tested under every given & obscure condition possible.

the margin of error between calculated results and observed results is unacceptable in this case.

you have to have a 500V source to charge a capacitor to 500V. ascribing this property to capacitors "one thing the stored energy in an In Line Capacitor (Electrolitic Types) multiplies by two-three times the Line Load." based on your experiment will not serve you well as you persue your carreer in electronics.

Charge Q on that Radio Station Secondary Circuitry maybe much higher than calculated the conventional way, under differing conditions such as power on & normal usage Vs everything On minus - The Load., nevertheless, approximate danger is danger enough to handle carefully. I don't envy your position };-)

it helps me pay for internet access.

Reply to
TimPerry

Rubbish. The voltage across an electrolytic is no higher than the peak charging voltage it is exposed to. I suspect you may be comparing RMS voltage with peak voltage, and calling the difference an "electrolytic fact".

Reply to
ehsjr

Hahahaha. You are incorrect. A capacitor simply charges up to the applied voltage. No more.

Charles Perry P.E.

Reply to
Charles Perry

I am very curious as to what you call "calibration".

A defective cap will still only charge to level of applied voltage, or lower. Never higher.

Hahaha. Capacitor charging is a theory that is well understood and defined.

I suspect you either measured incorrectly or you are missing something about the circuit.

Charles Perry P.E.

Reply to
Charles Perry

laugh all you want };-)

The cap measurement jumped to 500 volts across it (twice) then gradualy decreased., it was along time ago..... & don't remember if i had it on ac or dc volts.

you guys just don't want to be wrong., neither do I };-) maybe it was a receiver with components from outer space, you don't know }:)

The fact is that Capacitors Retain their charge even after you pull the equipment off the circuit., I agree it should keep to it's voltage, but, Have any of you constructed a Capacitor ? to know they are foolproof ?

Reply to
Roy Q.T.

Besides the applied voltage to the Cap couldv'e been more than household current, since radios have stages that amplify the voltage the capacitor in question could have been twice or thrice the line voltage., depending on the stage i pulled it from.

I don't want to argue any more about this it may be scaring away prospective Project Engineers that might have an actual Place to test out my hair brain experiences and conclusions };-)

Reply to
Roy Q.T.

??? The laws of physics apply to capacitors. They retain a voltage (that does decay over time, sometimes very slowly), but they don't mysteriously gain voltage once removed! Good grief. Do you even read what you write before you post it?

A failure mode where a cap mysteriously gains energy from nowhere?! Why Roy, you would be rich if you found that.

Charles Perry P.E.

Reply to
Charles Perry

Might have a place to test? I run a test lab. We charge and discharge caps quite a bit. One thing we use them for is to create large cap switching transients for testing equipment. Also, we do quite a bit of testing with the new supercaps: a few hundred Farads in the palm of your hand (yes Farads, not microfarads).

You see, Terry and I don't want to be wrong because we aren't, and can prove it.

As for calibrating your meter, is a 600 V DC source accurate to 0.05 volts good enough? What did you use?

Charles Perry P.E.

Reply to
Charles Perry

Some capacitors will regain finite terminal voltage some time after being discharged. Guess where it comes from? (Hint: This is not a "perfect" capacitor.)

Yes, I do believe in conservation of energy. :-)

Virg Wall, P.E.

Reply to
VWWall

Do what I do. If I see the name ROYKEY I just delete it unread. Simple.

Reply to
Rusty

I suppose you are referring to "bounceback". It is worse with paper caps. Better caps have better dialectric absorption (a measure of this phenomenon) and thus develop lower voltages. In all cases, however, the caps will end up with a voltage lower than rated voltage so it still kills Roy's idea.

Charles Perry P.E.

Reply to
Charles Perry

I don't care to participate in this match because I have a weak bladder, however here is a neat experiment for you.

Remove a crt from the tv of your choice. Discharge the second anode to the aquadag all you want. Hell, hook up a jumper wire between them for a few days.

Remove the jumper and let the 'ol tube sit in a corner for a week, then...

Go to the crt and put your thumb on the aquadag and your forefinger in the second anode button. Bet you don't keep it there long....!

Don't know why or how, but made more than one dude jump!

Reply to
C. Upskirts

Roy it occures to me that when you were fooling around with the old tube radio you pulled the main filter cap out then reattached it to the same point in the radio to which it was removed. next you turned the unit on and charged up the cap then removed it. of course you will measure high voltage on it.

however you have made several errors:

you seem not to realize that the radio has a step up transformer in it which will produce high voltage AC. you seem not to realize that the HV is changed to DC by a tube or solid state diode(s). you do not realize that had you connected the electrolytic in the manner you actually stated it very likely would have exploded sending shrapnel into and perhaps burning your hand. im making an assumtion here that it was a typical can rated at something higher then 500 WVDC (working volts DC)

i had to send my subspace transceiver out for alignment. it seems that only on the planet Binar can the proper digital node warp algorithms be programmed :)

yes this is correct.

, I agree it should keep to it's voltage, but,

now Roy, i think it's time for you to do a little more basic research on capacitors. i'll be happy to discuss power supplies and filters with you but you must do a little more groundwork. the internet is a handy place to study and research technical subjects such as this.

id like you to find out what a capacitor is and explain what "dielectric constant" means. find out why the British still call it a condenser. next tell me what "Q" stands for (and don't mention a Star Trek character) and how it applies to a resonant circuit. then give me an example of a high Q capacitor.

give us an honest effort here and then we can then discuss construction, functions, and even the quest for the perfect capacitor.

Reply to
TimPerry

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