Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fdesalvo on June 22, 2012, 05:34:12 pm

Title: DC Cooling Fan - neat way to run 'em
Post by: fdesalvo on June 22, 2012, 05:34:12 pm: There is an abundance of easily found info on how to run your DC fan using the PT's filament supply. What I didn't know is that the vast majority of these DC powered fans have internal rectifiers, negating the need to regulate the the PT's filament juice.

The info I'm linking to states you can connect your fan directly to the 6.3v supply without fear. If your fan has no/slow movement, a cap and diode may be added. Here's a really neat way to do this:

http://www.blueglow.de/FenFan.html (http://www.blueglow.de/FenFan.html)

Here's what I bought - 80mm

(http://www.quietpcusa.com/Assets/images/acoustifan80dp.jpg)
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: Tyrannocaster on June 23, 2012, 07:17:40 am: Neat idea and nice info page. Thanks.
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: Ed_Chambley on June 23, 2012, 08:45:43 am: Weber sells a little mod kit with a 2 speed switch. $15.00. Got one in every amp I have. I don't direct the fan at the tubes tho. I mount them at the preamp end just to get circulation.
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: fdesalvo on June 23, 2012, 12:00:16 pm: Just trying to pay it forward :icon_biggrin:

I've seen Weber's kits and they look like a great solution, as well. He's like a reputable version of Dan Torres.
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: The_Gaz on June 25, 2012, 03:10:57 am: I did not know about most DC fans having internal rectification. How would one determine if their fan had an internal rectifier? Simply just try and run it off AC?
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: PRR on June 26, 2012, 12:35:35 am: > DC fans having internal rectification

I would not put it that way. Most are one transistor and one resistor, two coils (trigger and power).

However I can see that for typical voltages (under 7V, perhaps a bit more), in reverse, nothing happens. So it runs slower, but OK.

And perhaps some makers are adding full-wave rectifiers to avoid problems with customers who don't know which way is which?
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: The_Gaz on June 26, 2012, 01:01:28 am: Quote from: PRR on June 26, 2012, 12:35:35 am
> DC fans having internal rectification

I would not put it that way. Most are one transistor and one resistor, two coils (trigger and power).

However I can see that for typical voltages (under 7V, perhaps a bit more), in reverse, nothing happens. So it runs slower, but OK.

And perhaps some makers are adding full-wave rectifiers to avoid problems with customers who don't know which way is which?

I am definitely one of those customers that doesn't know which way is which. Am I wrong in thinking that there is no wrong way to hook them up across the heaters? PRR, do you recommend a rectifier off the heaters even i the fan run directly off the AC heater winding?

My heaters are also elevated to 70vdc. on the CT. That shouldn't matter should it?
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: The_Gaz on June 28, 2012, 04:42:31 am: bump!
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: fdesalvo on June 28, 2012, 09:24:48 am: I bult the lil' rectifier circuit according to the link above and it works really well! The fan is damn near silent, but I wonder if it's output is enough to effectively cool things down. I guess all the amp needs is a little circulation.
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: schoolie on June 28, 2012, 01:47:33 pm: Very nice, fdesalvo! What do you think about venting the chassis? I'm thinking of installing the fan in a cutout of the back panel, above the PT. I'm more concerned about my filter caps than the tubes. Also, do you think it makes sense to install an inline 100mA fuse with the rectifier? I wonder if this fan could take out the heater circuit if it failed.

Thanks for the link!
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: fdesalvo on June 28, 2012, 02:13:57 pm: I honestly don't think it's worth fusing the fan - it draws such little current! Even if your chassis is hanging upide down, the chances of thetubes/PT cooking the caps is really slim. My chassis sits upright, Marshall style and the cab will have a long vent across the top. I'm going to position the fan where it's mounted in the cab itself to help move some air around the tubes/PT- not exactly sure where yet. Will have to wait for the cab to arrive.

Quote from: schoolie on June 28, 2012, 01:47:33 pm
Very nice, fdesalvo! What do you think about venting the chassis? I'm thinking of installing the fan in a cutout of the back panel, above the PT. I'm more concerned about my filter caps than the tubes. Also, do you think it makes sense to install an inline 100mA fuse with the rectifier? I wonder if this fan could take out the heater circuit if it failed.

Thanks for the link!
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: schoolie on June 28, 2012, 08:02:39 pm: I guess you're right about the fan fuse, as long as it doesn't short. I notice my chassis gets pretty hot, so I taped a thermocouple to my filter caps and the temp hit 110F after fifteen minutes of playing. I regret placing them above the tube sockets now, but a fan inside or outside the chassis would help.

Thanks!

Rob
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: fdesalvo on June 28, 2012, 08:19:43 pm: Don't go inside chassis- dust can be conductive.
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: schoolie on June 28, 2012, 09:19:07 pm: Quote from: fdesalvo on June 28, 2012, 08:19:43 pm
Don't go inside chassis- dust can be conductive.

Outside it is, then.
Thanks
Title: Re: DC Cooling Fan - neat way to run 'em
Post by: fdesalvo on June 28, 2012, 09:49:32 pm: Sho nuff