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Re: Rheostat
To: CRTech <crtech@crtech.org>
Subject: Re: Rheostat
From: Willie Barnett <wbradiolists@gmail.com>
Date: Wed, 18 Apr 2018 10:00:03 -0400
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First thought... $182?!?!? FOR A FAN?!?!? What's it made of, gold-pressed latinum?!?! YEESH!!!

The first question: What is the voltage at the fan terminals? Someone's suggestion of "a few diodes in series" is workable, but becomes cumbersome if more than just a couple volts need to be dropped. Let us know what that voltage is, and more precise answers will come your way. :)

Meanwhile, here's my 25c worth... ;) (Your credit's good.)

The fact that your replacement burned out so quickly, suggests to me that it's getting MUCH more voltage than it's designed for! For example, a 12v fan running on 24v will scream for a while, then burn up. Running a 12v fan at 15V may or may not burn it up, but it will certainly run faster than it should, and won't last very long.

Since you're talking about an STL transmitter, I assume this is in your studio building, which is climate controlled. Since the STL doesn't change power, the heat load will be pretty steady. I seriously doubt you even NEED that fancy fan control system! (Nor those $182!!!! fans!!)

You probably could "get away with" using a generic $5 computer fan (12V) and run it on 5V. (I assume it's a modern STL, with digital control systems?) You should be able to find a source of +5V. Power the 12V fan that way, and it will run slowly, but will move air. See if the unit is staying cool enough. If not, see if there is a 12V supply you can tap into. That should do it. Putting a 100uf cap (of at least double the voltage) across the fan will reduce any electrical noise it might introduce.

Willie...


On Tue, Apr 17, 2018 at 12:21 PM, Tim Roberts <tim@kmocfm.com> wrote:
The fan in our STL transmitter went out a couple years back. When we received the replacement fan ($182) we discovered that whatever controls the fan speed had gone out as well and to fix it we'd have to send it back to the manufacturer. Rather than deal with that I pulled the new fan as a backup for our STL receiver and we put an $18 fan I found on DigiKey in it
References: Rheostat
(Tim Roberts <tim@kmocfm.com>, 17 Apr 2018 16:21:12 -0000)
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