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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 :D 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.

If you don't want to damage the fan wiring, you can get a small computer power supply for about $20.
 

bogdanfirst

New Member
hm....i have seen some fans like this that function on 250V a.c. so i suppose there will be some for 120v if that is what you need.
you might find some to buy like that.
 

Nostrafus

New Member
Well most computer fands run at 9-12v dc, so it shouldn't be too hard to find a transformer/adapter/power supply for that.
 

kinjalgp

Active Member
You can even use old computer power supply for that.
 

Lizo

New Member
Thanks for the quick responses. So I just need a small transformer and splice the wires together. Will it matter how many fans I put on the end of it?

Thanks bogdanfirst and kinjalgp, but I dont really want to spend to much money on this little project and computer power supplys are quite big too.
 

daviddoria

New Member
"hm....i have seen some fans like this that function on 250V a.c. so i suppose there will be some for 120v if that is what you need.
you might find some to buy like that."

how would you run a fan on AC? wouldn't it constantly switch directions?
 

Lizo

New Member
Hmmm :? .

I dont particularly want to open up my amp and start attaching things to it because of the warranty. On top of the amp there is a big grill and I was planning on putting the fans above that, the slits in the grill are quite small but it does cover an area of 20x28 cm. Do you think it would be loud having possibly 4 fans blowing onto this grill because the surface it will be hitting, and also do you think it will be very effective? It obviously wont be as effective as putting the fans inside the amp but like I said Id rather not open it up.

Thanks,
Lizo.
 

kizzap

Member
having the fans ontop off the heatink is what happens in all new computers now. all the fans do is provide more airflow through the fins so that the components installed with the heatsink are kept cooler.

There should be no problem in using the fans as you say

Kieran
 

olly_k

Member
Wherever you put the fans, make sure there is adequate airflow that runs along the fins of the heatsink/s. I suspect the slots in the top of the amp case could dissrupt the flow of air and maybe make any effort non-justifiable but you never know. Also to help if possible make sure the fans pull the warmed air in an upward direction and also make sure cooler air can get into the case from a different point. Maybe have a fan pushing cool air in and a fan pulling warm air out? Where you put the fans entirly depends on the design of the amp really.
As far as AC fans are concerened, it isn't impossible they may cause interference with the amp so I would steer clear of this option. They are also more expensive I think!
 

Lizo

New Member
Thanks for the info, I never thought of having 1 in and 1 out. Ive found some cheap fans on eBay, £2 each, so it wont be too bad if it doesnt work.

Thanks again,
Lizo.
 

seeker

New Member
Hi Lizo,

If you get 12 volt 80mm fans (cheap ones) they pull about .15 amps.
Get a 12 volt DC , .5amp (or 500 MA, same thing) wall transformer and you should be ok for 2 fans. You need to stick them on with some adhesive so they don't vibrate off. If it takes a long time for the stereo to overheat and shut down as you said then any little bit of air will probably stop it, even aiming a small table fan towards the back of the stereo will probably solve your problem. Good luck with it and don't PI$$ off the neighbors! (unless you have to) :twisted:
 

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 :D :p :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.
 

Attachments

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 :oops: .

Thanks,
Lizo.
 

olly_k

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