I have a PCB which has a spot for a DC power jack, with three pins, but i'd like to use a 9V battery instead. Can anyone help me out on which pins are positive and negative?

 

DC power can be wired with the center positive, but not always. You can use a LED with a 1000 ohm resistor in series to establish the jack polarity.

The LED's short lead is the cathode.

 

For some reason my images won't upload, but the 2.5 mm dc jack is center positive. I see that the center connection corresponds with the pin on the back of the jack, so I know where positive lead goes. Does that mean the other two pins should be negative? And would you recommend a different power source than 9V? The chip has an operating voltage of 2.4 to 5.5V. I'm using the 120 Second Voice Recorder Module found here:
http://www.electronics123.com/s.nl;jsessionid=0a010a5c1f4397879837240b46ea9e10b67c688026c7.e3eSchuLcheTe34Pa38Ta38Lbhr0?it=A&id=2734&sc=8&category=2

 

Center is positive the other two can be negative, but You might damage the circuit if you give 9V where it says 5.5V max

 

hey guy,
according to your module ,it can withstand up to 24v. 9v to 12v can be chosen for reliable operation.And to know your pin configuration , the pin in contact with the anode of the diode connected to your voltage regulator IC will be positive(+9v)( the diode near your DC source connector) and the center pin is ground (0v)and the other is negative(-9v).Thus it will resemble + 0 - or - 0 +

 

hey guy,
according to your module ,it can withstand up to 24v. 9v to 12v can be chosen for reliable operation.And to know your pin configuration , the pin in contact with the anode of the diode connected to your voltage regulator IC will be positive(+9v)( the diode near your DC source connector) and the center pin is ground (0v)and the other is negative(-9v).Thus it will resemble + 0 - or - 0 +

Do you ever think twice before you say anything.
Or am I the dummy.....