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Small heat sinks on pills

Greg T

Greg T

WDX-945 (Jazz Singer) Upper Peninsula of Michigan
Sep 18, 2014
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Escanaba, Michigan
Anyone ever try using small heat sinks with adhesive pads on top of 2879s? Was thinking of trying this on my DX-500. The adhesive pads would hold them on and a slow turning internal fan with exhaust holes in the lid should move enough air with virtually no noise.
 
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I wouldn't.
The pills get hot and the adhesive will come undone. Then the small heatsink will move and short something out and poof.
The fan needs to be on the large heatsink.
Adding one to the top case can help but is not really needed.
 
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Xracerx13 said:
I wouldn't.
The pills get hot and the adhesive will come undone. Then the small heatsink will move and short something out and poof.
The fan needs to be on the large heatsink.
Adding one to the top case can help but is not really needed.
Click to expand...

The adhesive glue holds them to CPUs and such, so I was thinking it should hold on a transistor. Think not? They make sepcific thermal glue for such applications.
 
The top the transistors are not a good heat transfer medium, I don't think you will gain much for your efforts.

What is more important is that the heatsink and bottom of the transistors are as flat as possible, with a thin layer of heat sink compound , that is what dissipates the heat from the internal die.
There are pictures here from Nomad of a sweet sixteen that the transistors got so hot they melted the solder from the board.
Toshiba's 2979's are very rugged

73
Jeff
 
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These are Nomads pictures I grabbed from CB Tricks forum years ago if I remember correctly.
Solder melts at about 180°C , that's around 355°F
I believe he put it all back together and it worked.
Toshiba's were tough.
73
Jeff
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Screenshot_20231217-114050~2.png
 
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I recall BBi saying that polishing off the oxide on the heat sync makes a big difference.

And like the prices, not all heat sync compound is created equal.

If the amp has no fan, depending on the orientation of the heat sync fins, it might be worth setting it on its side. Convection is what cools the heat sync, so when convection brings the hot air to the bottom of the amp where it has to stop and move sideways under the force of the convection below, it stays warmer.
 
if you really want to help out your texas star amplifier turn it upside down.

a heatsink on the bottom of the component is counterintuitive.

turn the amp upside down so the heatsink is on the top. that way when the transistors heat up they send all their heat up to the heatsink. (hot air rises)

put a fan about a 1/2 inch above the heatsink blowing down on it and it will push the air across all the fins.

LC
 
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Greg T said:
Anyone ever try using small heat sinks with adhesive pads on top of 2879s? Was thinking of trying this on my DX-500. The adhesive pads would hold them on and a slow turning internal fan with exhaust holes in the lid should move enough air with virtually no noise.
Click to expand...
Your way over thinking things there my friend. Put a fan on the heat sink of any amplifier and you’re good. That’s what the heat sink is for.
 
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Blowing the air onto the heat sink fins directly from the fan removes more heat. The turbulence that comes with the direct air blast does a more efficient job of heat removal than the common base-amplifier setup with fans in the top cover, and air-inlet holes at one end of the heat sink. As the airflow passes along the heat sink from rear to front it heats up along the way. Transistors at the front end of the heat sink are being cooled by hot air.

The setup above is what we recommend.

73
 
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9C1Driver said:
Your way over thinking things there my friend. Put a fan on the heat sink of any amplifier and you’re good. That’s what the heat sink is for.
Click to expand...
I have a 140mm fan on the bottom. But if I get a bit long winded, the case gets pretty hot as well. I was thinking of also cooling each pill with a small heat sink and a large fan inside. You thinking no gains?
 

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