APACHE FAN

[AE1CT]

WHAT OTHER KIND OF FAN CAN I USE FOR THE APACHE FINALS. THE ONE THAT IS INSTALLED IS NOT WORKING AND I WANT TO REPLACE IT. IS THERE ANY IN PATICULAR THAT I SHOULD USE TO KEEP THE FINALS COOL.

[WA2ROC]

A 110 volt muffin type fan that will fit under "the hood" will work.

Newark, Digikey, Mouser, etc have them in stock.

[Pete, WA2CWA]

Mount the muffin fan, I use a DC fan, as a suck out rather then a suck in as was the original Apache fan. Sucks out the hot air and does not suck in dust and collect fur balls in the final compartment. .

[AE1CT]

Mount the muffin fan, I use a DC fan, as a suck out rather then a suck in as was the original Apache fan. Sucks out the hot air and does not suck in dust and collect fur balls in the final compartment. .

I HAVE SEVERAL 12VDC FANS HERE BUT WERE IS A GOOD PLACE TO TAP 12VDC FROM SO THE FAN WILL WORK.

[kb3ouk]

Sucking the air out always seems to cool tubes off better for me, my Hunter amp had a 110 volt fan inside that blew air across the tubes and out the side. You could tell that arrangement didn't work the best, the paint on the top of the cabinet was discolored from the heat going up, and there wasn't much air making it out the side of the cabinet, plus that fan was the noisiest thing I've ever heard. So I ripped that out and just sat a small 12 volt fan on top of the cabinet and left it pull the air out the top of the cabinet. The new fan runs at about half the speed of the old one but is silent and keeps the tubes cooler than the old one did.

[AE1CT]

Mount the muffin fan, I use a DC fan, as a suck out rather then a suck in as was the original Apache fan. Sucks out the hot air and does not suck in dust and collect fur balls in the final compartment. .

WERE IS A GOOD PLACE TO TAP THE 12VDC FAN SO IT WILL RUN EFFICENTLY

[WA2ROC]

There is no "best place" to tap a 12 volt DC for that fan. 

I would suggest a full wave bridge rectifier off the 6.3 volt filament secondary and a 100uf cap which would give you something like 13 volts DC.  A resistor divider set to give you about 10 volts to run the fan at a lower speed volts for the fan will also act as a bleeder resistor

[Pete, WA2CWA]

Since I solid-stated both the low voltage and high voltage supplies, the 5 volt secondary wiring was an good source point for powering a dc voltage tripler to power the 18 or 24 volt (don't remember what I used; it was 35 years ago and they're still running in there) DC fans I had. The fans don't run at max speed and are quiet. I also mounted the same type of fan over the modulator area. I think the fan is hanging off a bracket attached to the VFO case. All the 6146's and El-34's are still in use after over 35 years of service.

[KK4YY]

I always keep my eyes open for used 24VDC and 220VAC fans to use on the more common voltages of 12VDC and 115VAC respectively, as I'm not a big fan (heh, a pun) of wearing headphones. They run quietly at half voltage and are good to use where no fan was previously installed (but maybe should have been) or where a smaller fan had been used. A slow fan wafting a bit of air around an old boatanchor receiver or transmitter can help it live longer, and drift less, as it won't get so hot. When encountering the aforementioned fans at a hamfest always poo-poo the fact that they're a weird voltage - you may pay less for them.

-Don

[WBear2GCR]

What is not working with the old fan?

It is a basic shaded pole motor, they sell them new.
You can slip the old fan blades over the new ones shaft... assuming the
same size shaft, etc...

Usually they will work fine if they are degreased and relubed. I'd use a synthetic oil since it will not gum up.

They're hard to fry.

That might be simplest... of course a more modern muffin fan, as mentioned will do a better job, but there isn't a whole lot of room in there. And the original had the merit of being quiet, muffin fans are rarely quiet unless run substantially below rated RPMs...

For DC fans there are some nice temperature controlled variable speed circuits out there, that are very simple, based on a 3 pin regulator. They use a thermistor to detect the temperature and change the control voltage to match... usually there is a "pull up" cap that gets the fan spinning on start up, then you can slow it down to a minimum rpm (and noise) which is set with a low speed set resistor (or pot).

                     _-_-

[WBear2GCR]

Here's the idea as done by Nelson Pass.

This is for fixed speed, but the pot is the variable element, and can be changed out for a scheme like the thermistor... or a thermistor + transistor, etc...

[KA0HCP]

I disagree

Cheap muffin fans are noisy.  Quality muffins can be very quiet.  For few more dollars one can buy muffin fans designed to be ultra quiet.

www.newegg.com  is a good starting place.

[Pete, WA2CWA]

I agree that good quality DC muffin fans (set up as suck out air) are the way to go. My original fan was noisy, and since there was very little air movement out of the final cage due to the cabinet design, everything that was sucked into the final compartment had no place to go other then to attach itself to anything in there it could find including the motor.

[w5rkl]

I replaced the original fan in my Apache with a 120VAC muffin fan. I removed the original final cage top cover and replaced it with a thin piece of perforated aluminum available at most hardware stores. I cut the  perforated aluminum to fit the top of the final cage, mounted the fan to the new cover, then mounted the new cover and fan on top of the final cage, no new hole drilling required. I reused the original fan power cable and power plug, soldered it to the 120VAC muffin fan pins, then plugged it into the fan outlet next to the regulator tubes. The new fan blade's diameter, when powered up, covers over 70% of the final amplifier's top area, providing a significant increase in air flow into or out of the final cage, resulting in a much cooler final amplifier. I did the same thing, replaced the original fan with a 120VAC muffin fan, in my Heathkit Marauder HX-10. The 120VAC fan runs very quiet.

I have the fan blowing air down into the final cage and over a 3 year period, I have not seen any increase in dust collection in the final amplifier. Having said that, whether you have the fan blow air into or suck air out of the final cage is entirely up to you.

73
Mike

[W1RKW]

pulling heat out of equipment may not be good for the fan especially if it's a cheapy such as a sleeve bearing type fan. Try to find a ball bearing type fan.  Allelectronics at one time was selling ball bearing fans of various sizes for cheap.