Powering a 12v fan from my secondaries

[MrSimons]

Hi All,

I have finished my amp (LM3886 Bass amp) quite some time ago and much of my success is due to what i have read in this forum.

I recently bought some cpu heatsink/fan combos, there were about 100 of them in a cardboard box outside some shop selling for 1 dollar each (like little puppies you cant resist), so i got 3 of them...

I was thinking of using one of these as a heat sink for my amp since its in a quite small enclosure (an emptied out computer power unit). also because i am quite paranoid about the heat etc... its purely psychological, i know!

I was wondering first of all if someone has any experience with this kind of thing.
My transformer has un-utilised secondaries i think 7.5v - 0 - 7.5v which i would like to use for this matter.
I am guessing the fans are 12v, although there is no indication.

I am not too sure what implications something like that would have, and how should i power it from the secondaries, i probably need to give it dc so some kind of diodes or recitifier..
can the secondary amperage be a problem?

I am not the most experienced diy technician but i made it so far.

Much thanks, Gideon  :tu:

[armstrom]

if the transformer is center tapped then you could use the 15V secondary (don't use the center tap) to generate a 12V DC signal. You would need to rectify the AC voltage to DC and then run it through a 12V regulator to get it down to the proper voltage. What ever you do don't just hook up the 7.5V AC to your fan

It's also likely that the CPU heat sink isn't large enough. Maybe you should post some pictures.
-Matt

[MrSimons]

Thanks Armstrom!

I will probably do it like you said, useing a recitifier and a 12v regulator. i must admit that the idea to hook up the 7.5ac did cross my mind , thats part of the reason i decided to get some more info in the forum 

I will post a few picutres later today.

[J M Fahey]

Those little fans help, they´re definitively better than nothing at all. I once cured a client´s ADA Microtube100 with one of them. Obviously the 1U high rackmount chassis was marginally cooled. When used in stereo driving two 8 ohm Celestions, no problem at all, but when my client started using it bridged driving a single EVM12L, it would thermally shutdown after 1/2 hour of Heavy Metal. No physical space for a regular (80x80mm) fan, so a 40mm, 12V unit was pressed into service: no problems whatsoever in the last 3 or 4 years. I used a W004 Bridge and a 2200uFx25V capacitor. The almost 14dc Volts I get under load have not hurt it so far.