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In Reply to: RE: What happened to all the parts?? posted by vinnie2 on January 29, 2016 at 04:00:42
Especially for a cathode resistor which is typically of low-ish value.
Follow Ups:
Most cathode resistors I have used in the past have been for power tubes and I was using 25W or more. I guess it just got to be a habit.
Understood vinnie. Just be aware, neither the 45 or 26 you are running have a lot of cathode V to drop and current is small. The 45 will be the most demanding. As you know, to calc the power (wattage) dissipated:P = I x V (current traveling through the resistor x voltage dropped across the resistor, i.e. cathode voltage)
= 0.0342 x 41 (going by your preferred operating point and assuming you are not direct coupling to the 45)
= 1.4 WattsYour cathode R will be dissipating 1.4W! Ideally, I over-rate my resistor Wattage by 5, but that is very conservative of me and I break this rule occasionally if I know the parts are reliable. Mills are reliable. 1.4W x 5 = 7W. Hence, a resistor with at least 7W dissipation will do it very comfortably. A 5W resistor would also be doing it easy, so long as ventilation is adequate. A 12W Mills will be loafing.
For some context, my next build will use Mills 12W resistors to dissipate 5W in a moderately-well ventilated chassis. I am not worried.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Edits: 01/29/16
Do you still think the mills are the way to go after the posts about them being made in Mexico now and being a lower quality? I was all set to try some until I read those.
I'd try them.
I read someone's opinion saying the Mexico versions were higher quality; another's the opposite. No one is saying in what way, specifically.
More the point, I reckon the Mexico Mills are still a pretty decent product, versus the opposition.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
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