# Computer Fans

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#### Lizo

##### New Member
Hi all,

I have quite a large and powerful hifi and when its on for long peroids of time and at high volumes the amplifier gets very very hot. I have actually tripped the safety cut out before at a party I had a couple of years ago.

Anyway, I am having another party soon and Id like to cool the amp down. I plan on getting a few 80mm computer case fans as these seem ideal, I just need to know how to connect them together and how to power them. I think 80mm fans are usually 12v so I will need a 12v supply, also Id like to be able to plug it in to the mains, so Im guessing I will need a transformer.

Anyone got any ideas on how to put it all together, or any other sites with guides etc...

Thanks,

Lizo.

#### Nostrafus

##### New Member
Find out the voltage rating of the fans you plan to purchace then if it's something easy like 9v, get a 9v AC-DC adapter (Assuming the fans are DC) and strip the wires, and the fan wires, then get 2 wire nuts, and connect positive to positive and negative to negative, then connect them to the hottest metal part of the amp.

If it's something else you may be able to find a portable adjustable DC power supply with aligator clips, and do the same.

#### Gene

##### New Member
Sounds like a good plan. Consider mounting the fans on a small wooden frame - 1 or 2 fans should be plenty. The frame should have some foam rubber to isolate it from the amp case. A little should do since computer fans do not vibrate much. Usually, the fan wires are red for positive and black for negative. Just hook both fan positive wires to the positive wire of the wall transformer - follow the same logic for the negative wires. Also, if you opt for a wall "brick" transformer, be sure to get DC (not AC) if that is what your fans require.

#### Lizo

##### New Member
Thanks,

Hehe seeker, I dont think the neighbours will be pleased when they find out my parents arent in the country, theres 60 odd people turning up at my house and 3 live bands LOL!!! Ah well :twisted:

Yeh, ill look for some foam, thatll give it a nice and tight seal to the top of the amp case and should make it more efficient.

Cheers,
Lizo.

#### Lizo

##### New Member
Ive got hold of a copy of crocodile clips, and Ive put together a simple circuit. Take a look at the attachment and tell me if it would be suitable.
Basically I would like to have the option to reduce the speed of the fans rather than having them blasting away all the time. Are the values OK or could it result in damage occuring? When the variable resistor is at 200 ohms it says the motors are spinning at 1293 rpm and when its at 0 ohms it says there spinning at 4593 rpm. I know the motors I will use wont be anything like this but is that design alright?

Thanks,
Lizo.

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#### olly_k

##### Member
The motors will have to be in parrallel for a start, because each one requires a PD of 12V in your circuit they will only have a PD of 3v each - possibly not enough to kick-start them! Also bear in mind the motors will have to have a minimum speed to prevent them from stalling and the variable resistor will not drive that load without overheating - you will need to drive with a transistor or fet.

#### Lizo

##### New Member
Do you think you could draw out a rough diagram of how the circuit would look? How would I drive it with a transistor? Im useless when it comes to designing circuits .

Thanks,
Lizo.

#### L3wis

##### New Member
Hey lizo hehe! You found out about the transistors yet?

Lewis

#### olly_k

##### Member
Sorry bud I have been out all night and ready for bed now but will try to do somthing for tomorrow

#### Lizo

##### New Member
Thanks olly, I really appreciate all this help.

Lizo.

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