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Old 9th December 2014, 08:49 AM   #3801
Bonsai is offline Bonsai  Europe
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The simplest way to test this proposition is to read the temp at the base of the heatsing with an IR thermometer, and at the top.

I will try it tonight on my sx-amp after its been on for an hour and report back later.

Last edited by Bonsai; 9th December 2014 at 08:52 AM.
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Old 9th December 2014, 08:51 AM   #3802
nania is offline nania
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Being unaware of something doesn't necessarily make someone stupid.
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Old 9th December 2014, 09:14 AM   #3803
AndrewT is offline AndrewT  Scotland
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My stupid part is I can't understand what the english is telling me.
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Old 9th December 2014, 10:14 AM   #3804
jwilhelm is offline jwilhelm  Canada
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Quote:
Originally Posted by Bonsai View Post
The simplest way to test this proposition is to read the temp at the base of the heatsing with an IR thermometer, and at the top.

I will try it tonight on my sx-amp after its been on for an hour and report back later.
The only problem there is an IR thermometer won't give you a proper reading on a shiny surface. It'll be okay if your heatsink is dyed black.
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Old 9th December 2014, 10:31 AM   #3805
AndrewT is offline AndrewT  Scotland
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black body radiation does not mean it has to be non shiny black

The errors in reading black body radiation as one moves away from non shiny black increase quite slowly at first and then become nonsensical as shiny aluminium is approached.
That why these emergency blankets use shiny aluminium as insulators.

If you are using a non ideal radiator and measure the temperature at the bottom and at the top, the error from non shiny black will be similar for the two locations on the same heatsink.
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Old 9th December 2014, 11:05 AM   #3806
jwilhelm is offline jwilhelm  Canada
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My stupid part is I can't understand what the english is telling me.
I think he's trying to say there is individual convection cycles at each hot spot. Whatever the case air is moving so heat is being dissipated so life is good. If it doesn't move as much at cool spots it helps to even the temperature anyway. All this really isn't that important for listening to music. It might come into play if you are playing sine waves all day but to me that's not the reason I'm building an amp.
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Old 9th December 2014, 02:10 PM   #3807
Bonsai is offline Bonsai  Europe
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It's a basic comparative measurement, so absolute numbers may be out, but if there is a differential we should be able to detect it.

Here are the resuls

sx-amplifier powered up for 1 hour

Ambient temperature 20 C

Temperature at bottom of heatsink between fins 45.6 C

Temperature at top of heatsink between fins 51.0 C
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Old 9th December 2014, 07:28 PM   #3808
thimios is offline thimios  Greece
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Originally Posted by Bonsai View Post
It's a basic comparative measurement, so absolute numbers may be out, but if there is a differential we should be able to detect it.

Here are the resuls

sx-amplifier powered up for 1 hour

Ambient temperature 20 C

Temperature at bottom of heatsink between fins 45.6 C

Temperature at top of heatsink between fins 51.0 C
Temperature directly on the transistors body?
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Old 9th December 2014, 07:31 PM   #3809
east electronics is offline east electronics  Greece
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Originally Posted by AndrewT View Post
It does matter.
The top row of devices will run much hotter than the bottom row devices.
10degrees will make a big difference to temperature de-rated SOAR, if you are running at Tc=70C that becomes 80 for the upper row.

If it were Tc=50C that became 55, then there is not much difference.
Agree with Andrew on that

Small details like that make huge difference in long run and provide the reference between good and perfect designs
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Old 10th December 2014, 03:56 AM   #3810
Bonsai is offline Bonsai  Europe
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Temperature directly on the transistors body?

no - this was taken on the actual heatsink on the outside between the fins.
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