Monday, October 21, 2013

An Incorrect Guess About The Voltage Regulator

In a previous post of mine about the Zalman fan controller, I guessed that the voltage regulator was an LM317T. I came across a blog post about the same controller and the author said that the voltage regulator was a 7805. So I decided I had to verify that I was wrong. And I was. I desoldered the regulator from the board so I could identify it.
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Fairchild KA7805. I’m not sure what E33 means. “Although designed
primarily as fixed-voltage regulators, these devices can be used with external components for adjustable voltages and currents.”
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The resistor measures 708 ohms. I was wrong about it and the potentiometer as well. In-circuit measurment is not always ideal. Likewise reading resistor color codes in bad light through a small aperture is difficult.
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Violet, brown, black, black, brown, a 710 ohm, 1% resistor.
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The potentiometer measures between just over 0 ohms and 1K ohms.
Hey, I have some 7805 regulators in my parts library as well, so I can still make some fan controls if I want. Not that I will. And yes, I soldered it back together.

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