I assembled a PCB project I bought and must've done something wrong because it doesn't do anything. I tested the power adapter and got 6v when disconnected from the board so that's OK. Next I want to see if the DC power connector on the board is OK, but I'm not sure I'm doing it right.

With the power adapter connected, I put my meter probes to the two pins coming out of it on the back of the board and measured about .5v So I thought it must be bad. Before trying to desolder it (a skill I have yet to master), I thought it might be easier to solder a couple wires and a new connector to the back of the board first. I tested the connector first by putting the probes to the two pins and got 6v. Then I soldered 2 wires to the 2 pins on the board (other side of the existing connector) and used jumper cables to attach them to the new connector. Finally I tested the two pins at the board again and still get .5v. So I figure I must be doing something wrong. Can someone explain the right way to do this?

 

Post a picture of the board and indicate where you're probing incoming power.

If the board has IC's, power could be backwards. Adapters can be center positive (most common) or center negative. What polarity is yours?

 

Polarity? I tested it with the negative probe in the center and the positive outside and the voltage was positive. Does that mean it's center negative? I've attached a photo of the front and back. The red circle in the photo of the back is where I tested for power. The connector is on the opposite end from the potentiometer. I've also attached a photo from the manufacturer so you can see what the board looks like without parts. It is J2 in that one.

 

It looks to me like the board requires a center positive supply.

In the left picture, ground from the connector is between the two supports for the power jack. If you follow that to C11 at the bottom of the picture, you'll see the other terminal of C11 is labeled '+'.

The right picture shows construction of the jack. The center of the female plug contacts the pin in the connector. The barrel contacts the pin labeled '4'. This diagram was supposedly for a 2 pin jack, but it shows #3 for a normally closed contact. That connection is brought out to the side of the jack.


By connecting power backwards, you have damaged all of the electrolytic caps on the power rail. They only tolerate a reverse voltage of about 1.5V before they're damaged.

You didn't use enough solder in most of the joints.