<p>In pretty much EVERY case where something hasn't worked there has been one of two problems.<br />
1. cold solder joints. this is where you have solder ON the surface but it hasn't bonded with the metal. These can usually be found with a continuity tester and fixed by reheating and flowing the solder.<br />
2. backwards capacitors. The only ones you need to worry about are the electrolytic caps. These are the cylindrical ones. </p>
<p>Once in a while the problem is a solder bridge. This is where a blob of solder is connecting two points that aren't supposed to be connected.
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