Trouble with a stir plate build (running out of fans to sacrifice to my dark gods)

[Reckoning]

So I'm attempting to make a stir plate with a computer fan as per the post I found here …

https://www.homebrewtalk.com/f51/my-stirplate-cheap-easy-build-86252/

I've tried it a couple times but I keep burning up fans. I have a 12 volt power supply which has two wires, one solid black and the other lack with white dashes on it. I'm assuming that the solid black wire is the negative and the white dashed is the positive. The computer fans I sacrificed are 12 volt 0.6 amp fans with 4 wires (black, yellow, blue, and green). I though the black was negative, yellow was positive, green was “tacho”, and blue was PWM. I capped the green and blue and just used the black and yellow. The potentiometer I got from RadioShack matched the specs in the thread, but the posts were labeld “power”, “ACC”, and “ground”. I assumed that the “earth” terminal was “ground”, the “supply” terminal was“power”, and the “load” was the “ACC”. I hooked up the wires accordingly and when I plugged it in the fan would start and then after a few seconds it would stop and begin smoking. Thought the first fan might be too old so I tried another and the same thing happened. Do I have something seriously wrong with the identity of one of the wires or terminals?

Thanks.

 

[raouliii]

Are you sure that both the fan and the power supply are labeled for DC operation?

 

[big_len]

Just to confirm, your wiring should look like this ? Or indeed you may have put the potentiometer on the negative line, either is fine.

 

[Reckoning]

Power supply is AC. I didn't even think to look at that. Just pulled a power supply out of a box of old electronic parts, checked that it was 12 volt, and sallied forth. Everyone who systematically executed a family of computer fans for no reason raise your hand.:smack:

Thanks for the help everyone ... back to the drawing board.