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Old 18th October 2001, 10:23 PM   #21
haldor is offline haldor  United States
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Default BeO2

Hi DJK,

Where do you get your BeO2 insulators. I haven't been able to find anyone who sells them anywhere. Brush-Wellman still makes this stuff, but it is for internal use in IC's.

Got a supplier? I would love to buy some.

Phil
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Old 6th November 2001, 09:03 PM   #22
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You can try Silver grease, that improves very much, but be careful, it is ELECTRIC conductive..
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Old 6th November 2001, 09:21 PM   #23
haldor is offline haldor  United States
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Hmm, silver grease? Wonder if I will be able to "hear" it. Sorry, couldn't help the minor dig. I'm a philistine about some of the popular tweaks and making fun of cable lore is a weakness of mine.

I suppose any metal loaded grease could improve the heat transfer so this might help. On the other hand the thickness of the grease layers is a big factor in heat transfer (the thinner the better) and any metal chunks in the grease could cause you grief. I expect you would need an insulator that is quite a bit larger than the contact patch to make sure there was no possiblity of a conduction path through the grease (need to be really neat with the application of grease there).

I think the best answer may be to just use fan cooled, heat sinks without insolators mounted inside the chassis like recommended above. It would be a good idea to include a power interlock switch to remove AC power if the cover is removed. After all, I want the sound to electrify my friends, not the amp.

Phil Ouellette
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Old 6th November 2001, 09:23 PM   #24
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Default BeO2

Last time I checked for these (4 years ago), I could get them through Future Electronics in Canada , but only available in TO-3 and they were about $1 per unit, available in two thicknesses, both relatively thick.

If you check with http://www.thermalloy.com, they should be able to tell you where to get the Thermalloy units from some distributor.

In Norway, Eurodis sell Thermalloy. but I have been told (by others) that they are illegal in Europe.

Petter
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Old 6th November 2001, 10:01 PM   #25
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Please keep in mind that the BeO2 or berillium oxide washers can have an effect on your health similar to the effects of asbestos. I've been told that they aren't even legal in some countries in europe.

Rob
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Old 6th November 2001, 11:43 PM   #26
haldor is offline haldor  United States
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The safety problem with BeO2 was with workers breathing dust created during manufacturing by companies that did not take proper protective precautions for their workers. There are no health issues involved with the use of BeO2 products that I am aware of, unless you are planning on grinding them up and breathing the dust.

Brush-Wellman makes Be02 material, they sell primarily to chip manufacturers. IC makers use toxic chemicals and gases every day that makes asbestos look safe and cuddly.

Phil Ouellette
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Old 15th November 2001, 08:48 AM   #27
jduncan is offline jduncan  United States
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back to the heatsinks.....

OK, so can somebody tell me if my calculation logic is flawed here?

I'm building an Aleph 4 which will have each device dissipating approximately 24W.

If I take a maximum temperature for the junction at say 100 degrees (to give a large safety margin), I can have a difference in temperature of the junction to ambient of 60 degrees (taking max ambient as 40 degrees).

Given that i have a thermal resistance of 0.83 for junction to case and 0.2 for case to sink, the max thermal resistance of the heatsink to ambient (per length allocated to each device assuming they are equally spaced) should be:

Rsa = 60/24 - 1.03 = 1.47 C/W

Is this correct?
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