Re: Solder won't stick to back of pot?
I use GC liquid flux. Solder will stick to painted concrete with that stuff. I think the stuff is spruce tree sap. GC stands for General Cement and they go way back in electronics, hold the trade name Variac, and make a whole lot of chemical stuff for audio repair. They were the only liquid flux I could find. A word of warning the lids stick on the bottles really bad after you open the stuff use it close the bottle and let it sit. I use a Workmate bench to hold the square bottle and very carefully twist the cap back off with small channellocks. The wood workmate wont crush the glass jar. The channelocks will. That stuff works great. I use it on aluminum chassis ground star connections in amps. I never had too many issues with pots, but I do not use Alpha pots in guitars very often. Too much heat only affects carbon plastic element pots. Make sure you let the pot get hot enough for the solder to flow and stick to it. I rarely have any problems. When you see a bit of cloudy liquid run out around the solder blob it is ready to stick. I can just tell by looking if it will stick or not by looking at the puddle. When it starts to flatten out and run it will stick. I use 3 old Weller ESD safe pencils and 2 bases. One is teeny tiny, and the other two are standard pencils one with a conical tip the other a flat tip. Use a flat tip. You get better surface contact thus better heat transfer. I have a spare flat tip. When I solder up an amp I go so fast and do so many solder joints the tips cool off, and a grab another pencil so I can keep on going. A guitar control cavity has so few things to be soldered on pencil is fine. I also keep a gun, and big Bertha the monster pencil for chassis grounds. I just got an SMD unit for newer amps like Carvins. The teeny tiny pen will do SMD but I haven't the patience for it. Cleaning the back of the pot with denatured alcohol carefully can help. Some guys take a Dremel and rough up the back of the pot. I would stick with fine grit if I were doing that, and use a magnet to pick up any bits of metal sanded off. I started doing electronics way back when I was 7, and soldering soon after. A friend's dad was a EE and I thought electronics was the coolest thing ever. Anyway try a drop of GC liquid flux. You can burn it off, so you may need to add more. It will evaporate before the solder melts, so you may need to drip some onto the hot solder. I usually work with my bases set on high and work fast.