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Old 30th November 2008, 11:14 PM   #1
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Default heatsink tempurature?

can anyone shed some light on what is a reasonable heat sink temp for a zen amplifier. i know mr. pass says you should be able to put your hand on it when in operation but id like to know what a maximum safe operating temp would be. im using the irfp9240 and the irfp140 mosfets in the zen. id like to put a temp probe on the sink and see where it stabilizes.
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Old 30th November 2008, 11:22 PM   #2
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70 deg Celsius, maximum, 60 is better.
Don't believe your fingers too much, cos i choke the cigarette with naked two fingers and nothing.

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Old 1st December 2008, 02:01 PM   #3
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Default Re: heatsink tempurature?

Quote:
Originally posted by fligti91
id like to put a temp probe on the sink and see where it stabilizes.
Bear in mind that heatsink is cooler than transistor housing (tab). Put your probe directly to tab and see - you can check your transistor datasheet for safe and maximum ratings plus derating curve.
Rule of thumb is 60C (or famous hand test).
Just make sure not to short-circuit transistor tab and screw if using JK or similar temp probe with metal tip.
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Old 1st December 2008, 02:13 PM   #4
Magura is offline Magura  Denmark
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Default Re: heatsink tempurature?

Quote:
Originally posted by fligti91
can anyone shed some light on what is a reasonable heat sink temp for a zen amplifier. i know mr. pass says you should be able to put your hand on it when in operation but id like to know what a maximum safe operating temp would be. im using the irfp9240 and the irfp140 mosfets in the zen. id like to put a temp probe on the sink and see where it stabilizes.

Knowing that you plan to push your devices a bit harder than most, you must take a look at the de-rating curve in the data sheet. I would expect you to need a heatsink temperature around 40 to 45C, too keep your mosfet's alive.


Do the math, figure how much heat you need to get rid of, then see how much heatsinking you need to keep it at 40C.


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Old 1st December 2008, 05:45 PM   #5
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Default Re: heatsink tempurature?

Quote:
Originally posted by fligti91
can anyone shed some light on what is a reasonable heat sink temp for a zen amplifier. i know mr. pass says you should be able to put your hand on it when in operation but id like to know what a maximum safe operating temp would be. im using the irfp9240 and the irfp140 mosfets in the zen. id like to put a temp probe on the sink and see where it stabilizes.

remember, you might want use your amp on a hot summer day
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Old 1st December 2008, 06:01 PM   #6
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When it's summer time the room temps. go up to 27-28 deg. C, and the fans in my amp often turns up, but now only when I load the amp too much.
My fans turning on 53deg C and turns off on about 45 deg C, I have electronic thermal switch with relay for this auto cooling
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Old 1st December 2008, 08:53 PM   #7
Manu is offline Manu  Europe
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Quote:
Originally posted by zoranaudio
Don't believe your fingers too much, cos i choke the cigarette with naked two fingers and nothing.

Sweat ...
Walking on burning coal is therefore not a big deal ...

But generaly you can believe dry fingers as papa says ... above 50 C it becomes uncomfortable...



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Old 1st December 2008, 09:43 PM   #8
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i was trying to figure out where i was now to see if i added a fan if i had room for more current bias
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Old 1st December 2008, 10:38 PM   #9
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I don't know , well dry fingers maybe the reason, I was in the pub that moment, and done this after 15 years.
In the young years all cigg. was choked with naked fingers, and a friend of mine also tried but finished with a water boll on the finger.
Sometimes my soldering iron when I have nothing close to me is also fast cleaned with my left fing. and you can hear a high frequency tone like pssssssssst.
The limit is not same for everyone, in my case that limit of 50 C is u p above 75C with side of a hand.
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Old 1st December 2008, 11:12 PM   #10
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lol, you clean your soldering tip with your finger. holy sh...
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