If you have the style flyback cage that has the fly on the bottom and a sremovable shield on the top like my Magnavox U910 chassis than this is what I did, I cut a hole in the cage in front of the flyback about the size of the fan blades. Then mounted the fan right in front of the flyback. Then I opened up the top of the removable cover for the air to escape. It comes out rignt below the 6BK4. I left the set on for 2 hours and the fly was cool to the touch. I wired in 1 9v power supply tapping the 120v off the record changer supply. When the radio or the tv is on, the fan turns on. Not a big deal to me if the fan runs when the set is off, but when the power is off on the unit, fan turns off too.
Hey if these fans are placed on our flybacks, are you worried about dust and crap getting in there?