Hi DF96, a grid stopper...that's what it's called, and thanks for explaining the purpose of this resistor, to prevent oscillation. I tend stay away from carbon film because of my concern for instability but many seem to like carbon film or composite in this position. Do you have a particular brand of carbon film or metal film in mind? Your experience on this matter would be appreciated.
Instability? Are you getting carbon film and carbon composite mixed up? The latter can be unstable, over periods of decades. Some people prefer carbon comp for stoppers, but I don't think this is necessary.MGH said:
I don't worry about brands. The circuit is far far more important than component brand. Many (but of course not all) of those who worry about brands do so as a substitute activity for their lack of circuit knowledge, in my opinion.
Do you find this unusual?
Not so
I have been making my own for ages (think thousands of them, for over 30 or 32 years).
For both reasons: nil cost, but the main one is getting them in any odd value, such as .065 ohms , perfect for limiting at exact 10 A in short protection circuits.
I buy 0.50 mm diameter Constantan (although now it comes under the commercial brand CuNi44), which is solderable.
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.065 ohms is a short strip measuring 1 inch , as easy as they come.
I have 2 pads on the PCB separated by 20 mm, so the wire is parallel to it , 5mm away.
Wire resistance is 2.5 ohms/Meter , very easy to calculate.
So 0.1 ohms means 4 cm and so on.
100 grams of wire cost a few dollars and provides 1 year supply, how's that?
For higher values (0.33 ohms ; 0.47 ohms) I flat wind them around strips of "micanita" , a flat sheet material made out of mica.
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Are Kiwame resistors carbon comp or film? According to Partsconnexion they're carbon film.
KIWAME - 5 Watt Carbon Film Resistors
KIWAME - 5 Watt Carbon Film Resistors
as DF96 pointed out it a grid stopper resistor . Thus some inductance the small amount in those values should reduce not increase rf pass through . As for the plate and screen resistors more inductance is desired. Transformer coupled outputs state an inductance value , it part of how they work . All the signal passes through the grid resistor so try some ans see what you think.
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