[Coco] CoCo 3 Voltage Regulator heat sink

[Robert Gault]

Rick Taylor wrote:
> I had found a heat sink in a box - it's something I pulled out of an old
> switching power supply, I think, maybe 3.5 inches square aluminum with fins.
> I have it vertically mounted, seems to be adequate, but barely.
> Incidentally, while putting the thing vertical, I applied a bit too much
> torque and crunched the D880. I went to Jameco (with the mobo) and picked up
> these at their will call counter, with a little help from them figuring out
> what to use
> 
> <
> http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=33048&
> 
> I'm running it off a 200W AT style power supply. It's getting fairly toasty
> but it's been running for about an hour and nothing's caught on fire yet
> :-)
> 
> You can hold on to it for about three seconds before you go "wow! that's
> hot!" and let go. I'm not particularly good with electronics. What would be
> a better replacement that might run cooler?
> 

Picking an appropriate heat sink is not a trivial problem. I'd say if 
you can't hold onto the fins for more than three seconds, you are not 
dissipating heat fast enough.

Here is a url that explains in technical terms what is involved in 
picking heat sinks.
http://sound.westhost.com/heatsinks.htm

In short, the bigger the block and the more fins, the better the heat 
sink. However, if the transistor is dissipating to much power, a passive 
heat sink may not be feasible and a fan will be required.