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Old 15th April 2008, 02:22 PM   #1
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Default heatsink mounting Q

Hi all,

I've just embarked on putting together a mini-aleph for my full range speakers. I've really only done work with tubes before so be gentle with me

Believe it or not, but its actually quite hard to locate the info readily on all of this stuff!! So I've 2 questions:

1. heatsink: will a heatsink measuring 3" by 8" with 1 1/4" vanes with a 1/4" solid plate bottom be enough for one board? My second choice is one thats 4" x 8" with only 1" vanes.

2. Will a TO-220 mounting kit (insulating pad and bush) fit the TO247 package that the mosfets are?


TIA and sorry for what must be obvious questions....

Fran
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Old 15th April 2008, 02:42 PM   #2
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The TO-220 pad is too small for the TO-247. You probably won't need a mounting bush as the TO-247 hole is surrounded by plastic usually.
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Old 15th April 2008, 02:56 PM   #3
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Default Re: heatsink mounting Q

Quote:
Originally posted by woodturner-fran
2. Will a TO-220 mounting kit (insulating pad and bush) fit the TO247 package that the mosfets are?
if you cannot locate pads for TO247, take TO3 pad and trim the excess material.
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Old 15th April 2008, 04:21 PM   #4
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The BER118 thermal pads will work for TO-247 or TO3-P -- they are available from DK

You need to specify the number of fins if you want to guestimate the thermal impedance of the heatsink -- assuming 10 theta = 2.1
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Old 15th April 2008, 04:43 PM   #5
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OK,

thanks for that. The insulating pad then would be this one:

farnell link

jackiinj: I'll download one of the online calculators and see. AFAIK, the mini-A will dissipate about 45W per side so I'm aiming for a heatsink of about 1deg/W. Something like this one, but the one I have to hand has deeper fins:

second link


What do you guys think?

Fran
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Old 15th April 2008, 09:29 PM   #6
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HI

for FR aren't more appropriate the F2 current source ?
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Old 15th April 2008, 10:00 PM   #7
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I hear people recommending the F4 as well so I don't know for sure.


Fran
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