The next best thing to 2SK389 / 2SJ109 ? - Page 5 - diyAudio
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Old 23rd December 2008, 01:15 PM   #41
jims is offline jims  United States
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I would like 25.

Thanks

JimS
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Old 24th December 2008, 04:59 PM   #42
JimT is offline JimT  Canada
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Quote:
Originally posted by EUVL
> I can help with the North America distribution of your couplers. I'd be interested in 25 myself.

Thanks for the kind offer.

We need two more volunteers and still 375 heatsinks to be accounted for (assuming each person take 25 minimum).


Patrick
I just noticed the 25 minimum. I'll change my 10 to 25.


Thanks
Jim
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Old 24th December 2008, 05:50 PM   #43
EUVL is offline EUVL  Europe
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GB thread started. Pls check to make sure the stated quantities, etc. are correct :

Toshiba Dual JFET Heatsink


Merry Christmas,
Patrick
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Old 28th December 2008, 12:27 PM   #44
EUVL is offline EUVL  Europe
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200 to go.

http://www.diyaudio.com/forums/show...threadid=135359


Happy New Year,
Patrick
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Old 29th December 2008, 04:11 AM   #45
EUVL is offline EUVL  Europe
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125 to go :

http://www.diyaudio.com/forums/showt...35#post1697835


Patrick
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Old 29th December 2008, 05:01 PM   #46
EUVL is offline EUVL  Europe
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75 to go.


Patrick
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Old 29th December 2008, 06:10 PM   #47
Sheldon is offline Sheldon  United States
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Default low tech thermal coupling

thermal grease and shrink wrap, or cyanoacrylate glue.
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File Type: jpg transistor thermal coupling.jpg (21.6 KB, 1100 views)
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Old 30th December 2008, 08:24 AM   #48
EUVL is offline EUVL  Europe
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A well used solution, but try to bend the legs so that they will fit the pin layout of the 2SK389s, especially when used as a diff pair.

And compare the surface area that the glue comes into contact with the TO92 casing. The glue is normally the highest resistance. The TO92 molding compound is the next. Aluminium is easily a factor of 10 to 100 better than any polymer, even when filled.

Now only 50 to go.




Patrick
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Old 30th December 2008, 04:41 PM   #49
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by EUVL
A well used solution, but try to bend the legs so that they will fit the pin layout of the 2SK389s, especially when used as a diff pair.
True for 389, but this approach is very convenient for 170 or 74 diff. pair (and BJT diff.), which is what I was thinking of. Should have pointed that out.

Quote:
Originally posted by EUVL
And compare the surface area that the glue comes into contact with the TO92 casing. The glue is normally the highest resistance. The TO92 molding compound is the next. Aluminium is easily a factor of 10 to 100 better than any polymer, even when filled.
The glue is very thin, so the conduction is still very good. And for even thinner joint, the parts can be lapped flat with a little very fine wet and dry sandpaper.

Yes, aluminum is a better thermal conductor than glue, but you still have to transfer the heat to the aluminum, either with glue, with thermal grease, or some other bonding agent. And you have two barriers between the parts in your design (part-aluminum-part). Also the fit cannot be as good as two flat surfaces. Thicker interface, combined with larger surface area, is likely a wash.

However, if you want some extra cooling, the finned aluminum piece will provide that, the coupled pair will reduce it, compared to two separate parts.

Didn't intend to imply that it's not a clever solution for where it's needed.

Sheldon
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Old 30th December 2008, 07:54 PM   #50
EUVL is offline EUVL  Europe
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A typical thermal adhesive is an adhesive (e.g. epoxy) with about 60% filler content by volume. For expensive ones, the filler is usually silver or ceramic particules. Average size is 25 to 50 um. At our company where we live on such thermally glued joints, experiments showed that the optimal glue gap is about 0.1mm. Thinner than than, the glue does not adhere. The thicker the glue the higher the thermal resistance.

To minimise the effect of the glue, the simplest way is to increase contact area. In that respect, 0.1mm glue has about the same resistance as about 10mm of aluminium. So the resistance of the aluminium will disappear. True that in the heatsink, you now has 2 glue joints (part-al-part), but the reference is really the aluminium to which both parts are "grounded" to. So we can argue whether it is one or two joints in the chain. In any case, the increase of area due to contact around the cylindrical surface is 2x more than the flat surface alone.

As said in the first post, it is supposed to be directly pin and spacing compatible with 2SK389 / 2SJ109. If you don't need that, ther are many solutions otherwise.


Patrick
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