Basic soldering, circuit troubleshooting help.

[SideShow Bob]

It is a basic wig wag circuit using NPN transistors to alternate the rows of LEDs, and each board is independent. In other words, yes, the capacitor could cause it not to function.

[th3w01f]

It is a basic wig wag circuit using NPN transistors to alternate the rows of LEDs, and each board is independent. In other words, yes, the capacitor could cause it not to function.

I tried re-soldering but no luck, any advice on how to tell if that's the issue? I've figured out I can light opposite lights on the non-working board simultaneously by applying power to a single post of a light and a resistor but since I don't know what I'm doing that doesn't really tell me much.

[Circuits]

LEDs installed backward (reversed polarity) are like open switches... might as well not be there. And they prevent power from reaching components in the same series circuit they're part of.

[SideShow Bob]

Look at the schematic diagram, and jumper from ground ( DC - ) bypassing the transister and capacitor to the first LED, this should cause the LED string to light up. Then do the same to the other LED string.
If both strings work by doing this, you either have a bad transistor or capacitor.
Most likely caused from over heating while soldering or a reversed capacitor or transistor.

[jonny450r]

Like sideshow Bob said bypass the transistor and cap to insure function. Cap in backwards or a solder bridge on the transistor may have happened causing it not to switch properly. but most likely the transistor burnt up during soldering.