I need a schematic to go any further here...


... over to anyone with the schematic!

I don't have one unfortunately and probably would struggle to understand it (being a bit noobish)....

Also, if someone is able to guide me as to how to measure transisters on these aux boards (ie red on metal lug or black and what values should be?).  I don't think it would be as simple as one dry solder joint!
I found an additional dry joint on the middle transister as well.  They look like they are a P20N010 (?)

But seriously, thanks to everyone for helping thus far.