7805 Broken?

I have a 7805 regulator. I think I probably had it hooked up at first I can't remember. I have it hooked up with the capacitors going from ground to input and ground to output. It gets hot and shuts down within 10 seconds. Even when there is no load at all it still gets hot. Did I burn it out?

Perhaps you have the input and out put connected to the power supply incorrectly.

I've checked over and over again. It's a L7805CV, I connect pin 1 (pin on the left from the front) to input. pin 2 to ground and pin 3 (in on the right as the output. Is it even possible to burn these things out to where they overheat no matter what?

They can get very hot when overloaded or shorted, and still survive. I assume from your description it gets hot with nothing connected to the output.

Make sure your caps are the right way 'round.

It gets hot with or without a load. The negative leads from the cap are connected to the center pin. Thanks for all the input so far!

Can you post a (reasonable looking) picture ? What do you have powering the input?

diagram is here http://yfrog.com/0zdiagramop the black and red wires on the left go to my 12v 500ma wall wart

Double check that your middle pin is actually ground: I've seen a few chips that look like that that have pin 3 being ground, with pin 1 being input and pin 2 being output. Take a multimeter and test for continuity between the middle pin and the big metal tab, which should be connected internally to ground. Or use an LED. Also make sure your capacitor on the input is rated for at least 16V. You could be using 10V?

Is it even possible to burn these things out to where they overheat no matter what

Yes if you have damaged it they can and do fail in this mode where they just get hot. I have seen a few broken regulators fail like this.

Have you verified the wall wart isn't (or has not been) connected in reverse?

The regulator will get really hot if the output capacitor is internally shorted.


Yes but so will the capacitor.