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Hot Resistor - RCA 97K1 Canadian
2/2/2010 8:33:35 PMBrian
A resistor R17 gets very warm on this radio. The resistor itself is quite substantial in size meant to handle the heat, but in the circuit what causes it to be so warm?
2/2/2010 9:14:41 PMNorm Leal
Hi Brian

R17 will be warm in operation. It's across B+ voltage to ground and dissipates power. This resistor should be wire wound.

Would expect R14 to also be warm.

Heat is caused by voltage dropped across a resistor multiplied by current.

http://www.nostalgiaair.org/PagesByModel/326/M0015326.pdf

Norm


:A resistor R17 gets very warm on this radio. The resistor itself is quite substantial in size meant to handle the heat, but in the circuit what causes it to be so warm?
:

2/3/2010 7:42:57 AMBrian
Thanks Norm, Would there be any harm if I increased the wattage if I find another wire wound resistor of same resistance, so that it might operate a bit cooler?

:Hi Brian
:
: R17 will be warm in operation. It's across B+ voltage to ground and dissipates power. This resistor should be wire wound.
:
: Would expect R14 to also be warm.
:
: Heat is caused by voltage dropped across a resistor multiplied by current.
:
:http://www.nostalgiaair.org/PagesByModel/326/M0015326.pdf
:
:Norm
:
:
::A resistor R17 gets very warm on this radio. The resistor itself is quite substantial in size meant to handle the heat, but in the circuit what causes it to be so warm?
::
:

2/3/2010 9:36:53 AMRichard
:Thanks Norm, Would there be any harm if I increased the wattage if I find another wire wound resistor of same resistance, so that it might operate a bit cooler?

Brian, If memory serves me right (it has been a long time since college) the amount of heat (btu's/watts) generated remains the same no matter the wattage of the resistor, it is a function of the current through and voltage across the resistor. Having said that however; a larger resistor may be cooler to the touch based on its ability to dissipate that generated heat to the surrounding air. The amount of heat generated is still the same, it may \be absorbed by the air and moved away from the resistor (and hopefully the radio) at a faster rate with a higher wattage resistor.

Richard



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