How long does a resistor last?

ect

I

Noise?

It's well known that adding rumble and pop noise to a recording makes it sound more appealing to the phonograph crowd. And apparently makes them angry when you tell them that's what you've done.

You aren't going to see much nonlinearity, and resistors certainly weren't well picked -- 470k is close enough, and with 20% resistors, who cares anyway. What scares me more is, for instance, how a common Magnavox 6V6 PP amp uses 0.047uF for the coupling cap to one 6V6, and

0.0047 for the other. And the phase splitter doesn't split anything, it's just a cascaded stage. The only balancing is due to a voltage divider. Ewwww. I'd be willing to bet they did that intentionally, since LF distortion makes phantom bass. They used teensy output transformers, too.

Tim

Reply to
Tim Williams
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Serious question?

It depends on what it is made of. Also resistors are measured in ohms not watts. Genereally speaking the 1/2 life of the material is a good clue as to when it#s resistance will have doubled. SO don't use anything to radioactive. A typical value would be a million triilion years, if it fails before them take it back to the shop :O)

Reply to
Colin Trunt

You must be lucky if you choose them without taking into account the current they're handling.

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*Caution:  I drive like you do.

    Dave Plowman        dave@davenoise.co.uk           London SW
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Reply to
Dave Plowman (News)

In message , Colin Trunt writes

I don't know if it is a 'serious' question, but it seems to be a perfectly 'sensible' question.

Is this a misguided attempt at humour, or have you really not the slightest idea what you're talking about?

I suspect that the answer is very similar to that to "How long is a piece of string", but maybe there is someone who is prepared to venture a reasoned answer.

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Ian
Reply to
Ian Jackson

I think it depends on many factors, not the least of which are type - w/wound, c/composition, metal film etc - how close it's being run to its power rating, how much free circulation of air there is in the equipment, how close it's being run to its voltage rating, and its value, depending on type.

Resistors in high voltage circuits have a tendency to go high, for instance anode (plate) load resistors, screen feed resistors, resevoir cap voltage sharers or bleeders. Resistors that have a high value in the first place i.e. above say 220k, have atendency to go high in normal use, although some types, the old cc ones for example, are worse for this than more modern types. Low value resistors in low voltage circuits, on the other hand, seldom fail, unless they have done so in an obvious way - burnt out - caused by another fault downstream of them. There is no reason at all why a resistor in say the base bias circuit of a transistor, shouldn't last, unchanged in characteristics, pretty much for ever. Obviously many generalisations here, and there will of course be many anecdotal exceptions to the rule, but I think that gives a fairly useable answer to the question.

Arfa

Reply to
Arfa Daily

Not usually an issue. Anyway I can allways stick in a resistor to drop the current down to one it can handle. ;O)

Anyway if it lasts a day it should last a lifetime.

The usual solution is to add a heat sink.

Reply to
Colin Trunt

Proven! I was using some 100 Ohm resistors to limit current in a spark-gap ignitor for mercury short-arc lamps. The film resistor just BLEW off its resistance film on the first shot. I mumbled "oh yeah, I KNEW it was going to do that" and replaced with a bulk carbon resistor, and that held up for the life of the unit. You can guess, the pulse current was 20,000/100 or about 100 A. 200 A ^ 2 * 100 = 4 mega-watts for a couple microseconds.

Jon

Reply to
Jon Elson

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