I'm trying to wire together my old Stratish guitar in new & more interesting ways, but came across a problem; the wires from the pickups is of the "core+shield" variety, and as I wired the shield from the bridge pickup to the switch (as the wiring scheme I deviced demands), it melted through the insulation to the core wire, shorting the pickup. Any suggestions as to what I do wrong? I've read some references-in-passing to "heat sink"; what is it, and how & why should I use it? And while we're at it, I think part of the problem might be that I tried to avoid cold joints, by making sure (as best I could) that I heated the wire/switch rather than the solder, but I'm still not sure I managed to avoid them all around. My iron is marked at 30W, and I'm using (I think) a resin-core lead-free solder.