Little update - poked around it with a multimeter, everything seemed fine. Fuses all intact, coils all fine, diodes seem to resist one way more than the other, couldn't figure it. Re-melted all the new joints, added some solder on top of a trace that was bare copper in one corner but appeared to conduct just fine, re-melted a connector pin that didn't look too clever, put it back together again and it didn't work. Turned it off and on again a few times and now it works!? Bloody electronics. I look forward to it failing just when I really don't want it to..