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Author Topic: LM7805 Blues  (Read 2282 times)

llol_slim

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LM7805 Blues
« on: October 13, 2006, 01:17:31 PM »

Hi,
im sorry to but in like this..
I'm new to this forum and also to the modding scene.
I just tried making the 9v usb charger with an lm7805 regulator.
I did a "dry run" without solder and it worked perfectly using my voltmeter
so i went ahead and soldered it. Now it doesnt work ..
The voltmeter is reading .8
However the battery is only reading 7.6 ...
When I soldered the wires to the lm7805, could I have put the iron on for too long and damaged the regulator?
Like I said, sorry for butting into the topic, hope its ok
Thanks
LLol_slim
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viridius

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Re: LM7805 Blues
« Reply #1 on: October 15, 2006, 04:28:51 PM »

.8 volts?  You might have fried it.  You should test it under load, though: stick a 1k resistor across the output and measure the voltage developed across it.
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anthonyt

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Re: LM7805 Blues
« Reply #2 on: March 31, 2007, 08:53:34 AM »

An interesting thing about voltage regulators is that they act like a very high gain amplifier capable of going into oscillation if not properly damped. If you have not burnt it out like viridius suggested, it is possible that the output is oscillating too much. Place a .01uF or more capacitor close to the output leads and measure the voltage again.
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I LOVE ED

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Re: LM7805 Blues
« Reply #3 on: March 31, 2007, 12:20:37 PM »

You should use IC sockets next time.  That way, you won't risk burning your chips while soldering.
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YucA

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Re: LM7805 Blues
« Reply #4 on: March 31, 2007, 12:39:56 PM »

You should use IC sockets next time.  That way, you won't risk burning your chips while soldering.

i learned this the hard way... :undec:
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