The reason you needed a heatsink is that linear regulation is extremely wasteful of electricity. Running at 7V, you waste almost as much electrical energy in your regulation as you are using to run your fan! This is why I wanted to use PWM.
BTW, props to Uller. He's the one who helped me the most when I was learning electronics. He wrote that linear regulation article, then I wrote my fan regulation article with some input from him, and then he wrote another article on just PWM fan regulation.
Smart guy, and it's too bad I don't hear from him more often. He posted a lot on the HardOCP forums, but (last I checked) he stopped being such an active poster. He must have an ultra-busy RealLife(tm) schedule.
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