So You Made A Board and It Doesn't Work... Now What?

Having trouble with a circuit or a PCB...? Here are some trouble shooting tips:

• Only apply power when appropriate during trouble shooting. I know you know this but be aware because its easy to forget.
• Don't apply power or insert chips until you have rung out the power connections with an ohm meter. This will help you find "cold" solder joints. These are joints that look soldered but a little gray and dull. Re-flow any solder joints that appear "cold". When you test the resistance between where the power comes into the board and a circuit point that should be connected to it your meter should read as low as it goes. In other words the resistance should be the same as when you have the ohm meter leads shorted.

  

• Use a good resin core solder of the appropriate diameter (smaller is better because you have more control over the amount of solder being applied).
• ALWAYS USE SOCKETS for integrated circuits (swapping to find bad ones is infinitely easier). As Confucius says "Man who use sockets very wise, man who not use sockets like to desolder a lot!"
• Use a magnifier and visually inspect the copper traces for shorts or opens.
• Found a short...? Open it with an Xacto knife (or similar tool).
• Found an open...? Close it with some copper wire and solder.
• Visually inspect the board for unsoldered leads.
• Unsoldered lead...? Solder it.
• Visually inspect the components for correct values (replace if necessary) Great Resistor Calculator.
• Always test physical components (switches, LEDs, jacks) before installing them (they do make bad ones).
• Swap active components (OP-Amps, Logic Chips, Transistors) for known good ones (sockets are our friends). Cut the pins off of and throw out bad components (so you don't inadvertently use them again).
• Make sure that diodes are oriented correctly (a diode installed backwards can wreak havoc).
• Do you have a shorted component: diode, transistor, etc... it happens.
• Make sure ICs are inserted correctly. An IC installed backwards will get VERY hot and become expensive garbage very quickly.
• Make sure that transistors (bipolar or FET) are oriented correctly. If you have obtained a cross-referenced transistor ALWAYS check the pinout to insure that you get it oriented correctly especially FETs. D-G-S can turn into D-S-G in a cross ref'd FET.
• Make sure electrolytic caps are oriented correctly (an electrolytic cap installed backwards can wreak havoc too).
• Look over the parts layout and board VERY carefully and make sure that every part is the correct value and that every jumper is installed.
• Is one of the IC pins bent under instead of plugged into the socket?
• Is a socket pin bent under instead of going through the board?
• Did you forget a connecting wire on the panel?
• Did you forget a connecting wire between the board and the panel?
• Did you run a connecting wire on the panel incorrectly?
• Did you run a connecting wire between the board and the panel incorrectly?
• Are your batteries alive?
• Does your power supply work?
• Go over the panel drawing wire by wire and recheck every connection.
• Go over the panel to board wiring drawing wire by wire and recheck every connection.
• Read any circuit description that is provided and use it to provide yourself with trouble shooting clues.
• Seek a local electronics resource (teacher, professor, electronics repair shop, friend) to help you.