Quad fan for cooling amp

[uki]

Hey guys!

I put together this contraption to cool down my amp it does get really hot after an hour or so.

All four fans are connected in parallel and a 12v 3A power supply is feeding it, recently one of the fans died(now replaced),
all are 12 volts, one doesn't have label no way to know the amps it need, the other three are: 0.18A, 0.17A, 0.15A, the one that stop working 0.2A.

Is there something wrong with this arrangement?

Thanks in advance!

[acheld]

Should be just fine with the robust power supply you have.  (As long as the cabinet does not lift off!)

Those fans do die on occasion.

That is a lot of AirPower, though.  Makes me wonder 1) why you need so much cooling, and 2) there may be a more efficient way of providing the airflow to the right parts that need it.

[uki]

(As long as the cabinet does not lift off!)

Never crossed my mind !!

Those fans do die on occasion.

Well they all have been removed from old computer power supplies.

That is a lot of AirPower, though.  Makes me wonder 1) why you need so much cooling, and 2) there may be a more efficient way of providing the airflow to the right parts that need it.

1- The amp do goes mighty hot after an hour or so specially in the summer!! 
    Creative layout, power tubes are closer to each other than it usually is.

2- I have a bunch of busted old computer power supplies, so it was cheap to make!

Good idea to use a fan speed controller?

[acheld]

Good idea to use a fan speed controller?

Probably not worth the bother . . .   

One of my projects needed a fan due to the enclosure I was using, and so I incorporated computer fan to draw air out.    I was worried that the fan might be too loud, and so dropped the voltage to the fan via resistors.  Truth is, you can barely hear the fan . . . even at high speed. 

[uki]

[ dropped the voltage to the fan via resistors.

How did you do it?

[PRR]

"all are 12 volts, 0.18A, 0.17A, 0.15A"

Say 12V 0.17A. That sounds like a resistance, V/I=R. Which is 70 Ohms.

If you put a 70r resistor in series with a 70r fan, you expect about half voltage. That may be too slow. But a 7r resistor in series with a 70r fan you expect 90% or very little effect. So pick something in the middle, 50r or 33r per fan.

Dissipation is more tedious. But note that (unless the fan goes short, which I have never seen) the resistor can't dissipate even 1/4 of what the fan sucked at full voltage. 12V*0.17V is 2.04 Watts. So a half-watt plus derating, use 1W.

[uki]

Thanks @PRR

Well I do not have the resistors and now days I rather use what I got instead of buying, but, I got some other stuff and another option came up, a little circuit for fan speed controller, I changed it a little, R1 smallest pot I had is 5k, the R2 in place is 270r and T1 is TIP41, T1 does get warm w/o a cooler. It does works, in the minimum set 5.4v the fans get quiet and at maximum 10.4v.

Any though about it?

[sluckey]

Put a heatsink on the transistor.

[PRR]

Put a heatsink on the transistor.

Yes, it is on the edge. An at-home amp may run forever on a naked TIP29. Go out to a paid gig and USE the amp, you are asking for a melt-down.

I've been blowing tube amps for 45 years and I still don't like it. The noise. The one more thing to fail at a bad time.