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Old 13th January 2002, 08:38 PM   #1
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Join Date: Jan 2001
Default heatsink and other

hello.
i have two heatsinks with 0,35 K/W for aleph 60. Is this
enough.(for one chanel)
How big transformer i need for one chanel.
What is happend if i do not use a thermistor?
Is the R19 correct value?

Janey
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Old 13th January 2002, 09:17 PM   #2
Freddie is offline Freddie  Sweden
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Join Date: Oct 2000
Location: Sweden
Referring to the Aleph 60 Service manual, the power consumption is 220W per channel.. This means you have to dissipate 110W per heatsink.

110 * 0,35 + 25 = 63,5C (38,5 above ambient)
That is a little too hot.
The original Aleph runs at 25 above ambient.

I'm using a 0,17K heatsink per channel for my Aleph 30.

R19 is marked 5622 ohms in the service manual, but that can't be right. It should have higher value.. I don't know the correct value though.

/Freddie
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Old 13th January 2002, 09:25 PM   #3
paulb is offline paulb  Canada
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Join Date: Jun 2001
Location: Calgary
You need to add the case-to-heatsink thermal resistance as well. The spec on the heatsink is probably heatsink-to-air. When you get this much power, both are significant.
There have been many other posts on this topic, do a search and you should be able to find something.
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Old 13th January 2002, 09:33 PM   #4
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Default About not using an thermistor

If you don't use an thermistor in series with the primary of the transformer you'll get an increased inrush current. Depending on the size of the transformer and filter capacitors the inrush current may cause a blown fuse.
Amplimo (manufacturer of toroidal transformers in Europe) suggests the use of two 5Ohm thermistors (NTC-resistors) in series with the transformer if it's rated above 500VA.
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Old 13th January 2002, 09:50 PM   #5
Geoff is offline Geoff  United Kingdom
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Janey

The correct value for R19 is 56k2 (56.2 kohms).

Geoff
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Old 13th January 2002, 09:51 PM   #6
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Location: Lethbridge, Alberta
R19 should be 56K, I obtained this figure from Mr. Pass . Factory Aleph60s' have a transformer with a 600VA rating. You can omit the thermistors but don't use additional filtering.

Brett
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