Better cooling as life insurance for the Potentiometers

[Jón]

I have meanwhile read a lot of complaints about failing potentiometers, which had me checking the temperatures and cooling of my Kaze Server.
Indeed a single Scythe Slipstream (120mm 1200RPM) had the heatsink of the potentiometer where it was connected rise 40°C above ambient at about 600 RPM and heats the neighbour heat sinks up about 10°C each as well. The tiny heatsink could at best be capable of 40 K/W which means it is dissipating 1 W. The Slipstream being specified as 0,26A = ca 3 W and the potentiometer might be burning half of that = 1,5 W, so at least 0,5W are going out the backdoor, means heating the neighbours etc.
The Kaze Server is specifid for 4 channels of 1 A each. Throttling all those by 6 V each means you need to get rid of 4 * 6W if I understand the physics correctly. If we accept 80°C @ 2o°C ambient we need a heatsink with 10 K/W per channel or a shared one with 2,45 W/K.
The Kaze Server heatsinks are underdimensioned by a factor of 4 if I am right.
That's the theory. Thinking practical, 1 A is a lot for a cooler fan and it's not desirable to burn so much energy through simplistic voltage regulation. Even installing a capable heatsink would just bring up the next problem.... moving enough air to transport the heat out of the 5,25" slot. How about a fan to cool the fan controler

For my peace of mind, I invested 1,40 € at Conrad, who happens to have a shop just atround the corner, and bought two heatsinks, part number 188255-24. They are reated at 8,5 K/W each and I plan to fix them on top of the existing heatsinks, joining them into a combined one with approximately 3 K/W. That should keep my potentiometers below 40°C in any realistic scenario.

Jón

[Jón]

I must admit, that my advents into theory was probably crap
I suspect that the hot components under the heatsinks are some kind of VRM IC's which should stand for a more efficient solution (than pot's only).
Nevertheless my temperature measurement was real, indicating about 50% efficiency only (in that case)
So What ? .... My cute little mod works as expected. I didn't bother to measure as the heatsink now only heats up a little bit