External Rack Fans

[MesaGod666]

Ok. So, I've been going through tubes about every four months. I gig 4 times per week. I have a huge 28 space rack and I'm thinking about getting a rack mounted fan in the rear to better cool my tubes. Any suggestions?

 

[RectoStudioGuy]

I've been using external fan systems for years. Have designed many of my own that operate on timed relays and thermal switches much in the same manner as your household thermostat. For next to no $$ you can build your own to suit your needs. Of course something to remember, if your rack is fully enclosed along with incoming cooling air you would best be served to have exhaust fans as well, usually near the top where the warmest air collects.
There are production models available such as:

http://www.activethermal.com/System_2_Rack_Mount.htm

and many others like them.