How hot is too hot?
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Budgie

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Having just moved my new Skeres into a chassis I thought I would measure the temp before closing it up. The power supply heatsink is running at 125 degrees (F not C
) and the mosfet/ccs heatsink is around 112 degrees. The power supply is a Power One, dual voltage type. Adding more heatsinking will be a pain at this point, so should I add a fan??
 
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AssafL

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112 deg. F is hot?


Seriously, my class A back home runs at almost 100 deg C (Japanese TO-3) for many years. Can cook eggs on them.


Fans just add noise...
 
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Budgie

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Wow, thats hot! I go by the "how long can I hold a finger on it before I smell burnt flesh?" test, and I figured I was at the hot end of acceptable. I start worrying about life expectancy of components when too hot, but I guess I am overly conservative. I re-adjusted the bias down to 130 mills per channel and I do not hear any differance, so I will use that for awhile and see if I am happy with the sound. (tweek urge will surface again, I'm sure).

Thanks for the reply,Assafl.
 
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KurtW

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Most devices are specified for a maximum junction temperature of 150 degrees C. This is the spec for the silicon inside the package, so you have to look at the thermal resistance of the package. A TO-92 package, for example, has a thermal resistance of 200 degrees per watt from junction to ambient. So if your running 0.5 watts through this device and have a ambient of 25 degrees C, your junction will be at 125 degrees C which would be within spec. But if your ambient is 50 degrees due to other devices putting out heat, then you would be right at the limit.

If you are using heatsinks, they also have a thermal resistance that should be taken into account. This can vary widely depending on the heatsink, from below 10 to 100 degrees per watt.
 
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Budgie

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Thanks Kurt! I guess the down side to using surplus parts is having to guess at values, such as the heatsink ratings. I am sure I am in the safe area of operation now, though. Thanks again guys!
 
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