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Old 19th September 2003, 09:36 PM   #1
Jaac is offline Jaac  Netherlands
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Default [Aleph5] Heatsink burn-in test

Hello there!

While we are collecting all our parts for our Aleph5's we came around some nice heatsinks measuring 33x18x38 mm. Perhaps we can use them? We gave it a try and connected 4 Caddock 9100 resistors (25 ohm / 100W) to it in parallel. We add a nice and cute PSU to them and fired the whole thing up.
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Old 19th September 2003, 09:37 PM   #2
Jaac is offline Jaac  Netherlands
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In order to calculate the thermal resistance we dissapated 100Watts in total devided over the four resistors and waited. After an hour we read a steady 53.1 'C. With an ambiant temperature of 23 degrees this means: 53.1 - 23.0 =~ 30 'C. @ 100Watts.
R(th) = 30 / 100 = 0.3 K/W.
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Old 19th September 2003, 09:39 PM   #3
Jaac is offline Jaac  Netherlands
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Now some fine calculus for beginners:

An Aleph5 dissapates 150Watts per channel, therefore we get 150 x 0.3 = 45 'C above ambiant. At 25 'C ambiant this means a surface temperature of 70 'C. Hmmmm.... This is quite hot!

Now to our question: is this TOO hot?


Having that nice PSU looking at us with its maximum ratings of 40V / 75 Amps we couldn't resist to fire the whole setup to the max. Putting 40 volts over those 25 ohms resistors this meant a total dissipation of 250Watts!
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Old 19th September 2003, 09:45 PM   #4
Jaac is offline Jaac  Netherlands
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And yet another pic: the PSU naked.

Maybe we could use this for another pass labs project in the future.
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Old 20th September 2003, 08:55 AM   #5
MikeW is offline MikeW  United States
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Default too hot?

You would be better off with two per channel or some fans.
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Old 20th September 2003, 09:42 AM   #6
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Quote:
Originally posted by Jaac TheMaster
Now to our question: is this TOO hot?
IMHO Yes it is too hot. You should generally consider 55C about as hot as you want to go and I certainly wouldn't go over 60C.
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Old 21st September 2003, 08:33 AM   #7
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Default Hot Hot Hot

Hi,

I order for a product to go en the market, any surface may not exceed a temperature of more than about 50 - 55 degrees (Centigrade) this is the temperature where most people would not like to keep a hand or finger on the hot surface.

IMHO: The semi's mounted on the surface would not like to be sitting at 70 degrees for 10 years. I reccomend to not have the sinks hotter than 50 - 55 degrees.

Also you must think of the room temperature during summer might exceed 30 - 35 degrees (where I live we don't use air condition)

\Jens
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Old 22nd September 2003, 02:57 AM   #8
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OTOH, 0.3K/W is just perfect for a channel of Zen v4...

...where did you find this heatsink, and how much did it cost?

/andrew
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Old 22nd September 2003, 10:26 AM   #9
Jaac is offline Jaac  Netherlands
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The Heatsinks where mounted on an switching power supply that we bought last winter in Rosmalen in the netherlands on a radio market (b.k.a. Veron ) for 7,50 euro each. The heatsink self is a special made i think because the fins aren't spaced the same over the lenght of the heatsink.

gr jaac
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Old 22nd September 2003, 11:44 AM   #10
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Did you test it like in the photo ?, if so redo the test with the heatsinks standing upright and with spacer between the floor and heatsink so you got maximum convention. You just made your heatsinks more efficient

Ralph
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