Here are the troubleshooting steps I usually follow:
1. Visual inspection of all solder joints. Look for cold solder joints, missing solder joints and debris that could cause shorts between adjacent pads.
2. Visual inspection of all components. Look for part number, value, orientation and damage.
3. Check voltages on ICs & transistors.
4. Divide the search for the problem into functional blocks. Does the signal get to the input of the 1st stage? If it does, move on to the input of the 2nd stage, and so on.
Here is a troubleshooting philosophy that has worked well for me:
a) Look in all the easy places first. That's why visual inspection is at the top of the list. It requires no test equipment or electronics knowledge. The vast majority of the time, inspection finds the problem.
b) Be willing to turn over every rock. Don't mentally eliminate a possible search area because "that can't be it" or "it's too hard to check that part."
c) Be systematic. Resist the temptation to randomly replace transistors and ICs or reflow every solder joint without inspecting them first. Take notes of where you looked, what you found and what you did about it.
d) Consider the possibility that more than one thing could be wrong. Sometimes multiple circuit problems mask each other.
e) Don't give up.
f) Ask for help.
When you do ask for help, post hi-res pictures of both sides of the board and all the wiring. If we're going to help you, we need to be able to read the color bands of all resistors and the part numbers on all of the ICs, as a minimum. The first thing we're going to do is inspection. If you make that hard, then you won't get the help you need.
Identify every place where you deviated from the Build Docs. If you built a board before the build docs were published, then you are SOL until they are available.
You have to be committed to troubleshooting. Don't expect us to do all the work. Be responsive. If you won't have time to work on it until the weekend, don't ask for help on a Monday.
