Size of resistors?

[bluzmn]

Have the materials and manufacture of resistors improved so much that resistors are now half the size they used to be? The reason I'm asking is that I ordered some resistors from AES and the supposedly 2 watt 470 ohm resistors that they sent me are half the size of (what is on the schematic) a 1 watt 470 ohm on a SF Champ I'm working on. I was about to call them to complain but I decided to check out the 1/2 watt resistors they had sent me; they were also 1/2 the size of the 1/2 watt resistors in the amp. Did they send me the right parts?

[Techknowman]

Depending on the materials used in the resister.
Metal oxide resisters can be much, much smaller and handle the same current as a standard carbon film resister in the larger size.

[MWJB]

A 1W Carbon Comp resistor will be somewhat larger than a modern metal Oxide 3W resistor. Not that you would put a 470ohm 1W resistor in a champ, unless it is a screen grid resistor, the only 470ohm on the original schematic is the power tube cathode resistor, you should be using a 4W or more, wire wound resistor here, make sure that the 25uf bypass cap is rated for 50v minimum (not 25v) and mount it away from the resistor body because the resistor gets hot.

To determine a resistor's wattage rating, square the voltage drop accross it in volts, then divide by resistor value in ohms, e.g. a champ might read <30v accross the cathode resistor, 30*30/470 = 1.9W, double it to be on the safe side and 4W would be the minimum, but any amp parts supplier will stock 470ohm 5W wire wounds, so use them.

[jrfrond]

HALF the size they used to be???

Open up an amp from the 30's or so and see just how BIG a half-watt resistor was. They dwarf some current 5-watters!!!

[bob p]

http://music-electronics-forum.com/t21277/

[thomasdy]

Resistors are used to make transducers sensor subsystems.Transducers are electronic components that convert energy from one form to another, where one form of energy is electrical.A resistance depends on the light, or LDR, is an example of an input transducer .Variations in the brightness of the light that shines on the surface of the outcome LDR changes its resistance depending on resistance is to reduce the flow of electrical current.