Sodering question...

[TinIndian]

Here is a post I made earlier on this subject.

Flux is used to clean the area were you are going to solder. It helps the solder "wet" to the lead and in your case, I assume, terminals. I would recommend eutectic solder which is 63% tin/37% lead. Much easier to work with than the new lead free formulations.

When you make your solder joint, first apply a small amount of flux where you want the solder joint. Next apply a small amount of solder to the CLEAN tip of the iron. It is very important the tip is clean for proper heat transfer. Next touch the tip to where you want to make your joint, the flux should "sizzle" as it cleans the connection area. Quickly and carefully feed the solder wire onto the tip where the joint is so it contacts both pieces of metal. If the tip temperature is hot enough it should flow the solder and make the solder connection. Try to keep your contact with the joint to 3-4 seconds to avoid damage to other components. It will take practice to make a solid joint and remember, more solder is not better.

I would recommend a rosin flux and rosin cored solder wire. It is usually active enough to make a good connection on dirty/old components. I would clean the connection with a little alcohol to remove exces flux. There are also no-clean varieties of flux but would be harder for the average person to get ahold of and might not be the best choice for old pots anyway. I would stay away from Organic Acid fluxes. Although they work very well they will corrode metals if not cleaned properly.

 

[96tbird]

I used to fix circuit boards for video games. We only used minimum 45 watt irons to heat quick and get out! Low watts are useless for ANY purpose... garbage! Well maybe you can join tiny wires with them, but for any component work, they stink.

It will take a long time for a pot to be destroyed by heat when heating the back, heat has to travel to the front metal shaft, down that to the wiper. The plastic part you see on the front where the lugs are mounted is a fibrous resin that is heat resistant to a point, but the metal case will heat rapidly before the resin is in danger if you have a minimum 45 watt iron.

When heating the lugs, they are crimped directly to the resin board and connected to the resistive carbon "track" etched on it's surface. you can cause damage quickly so you must be quick with the iron, five seconds, and prepare the lugs properly before making the joint.

Have a damp sponge ready and wipe iron tip on it constantly to clean excess solder and black gunk from tip of iron, before and after each joint.

Clean pot case and lugs by scuffing lightly. apply a PINHEAD sized dab of flux, especially to pot case (dirty). Solder will flow to wherever flux has melted so use flux sparingly.

Touch iron to flux spot on component. after a second or two touch solder JUST beside iron tip, as soon as it melts remove solder and iron. Just a dab. Let it cool a minute.

If it's a lug, try to just get solder on the loop of the lug, don't fill the hole. bend wire "J" shaped to hook into lug, heat and add a dab of solder. Hold perfectly still ten seconds. Wipe the iron clean.

Pre apply solder to wire. Remove insulation leaving more exposed wire than you need, say 1/4 inch. Touch iron near the wire insulation, touch solder to wire and as soon as it melts, draw iron to tip of wire: solder will flow towards the iron. Perfectly tinned wire, trim it to length.

Melt solder on part again and insert wire to pool of solder. Remove iron, hold wire still 10 seconds. Wipe the iron clean. Check to make sure joint is shiny; if it's dull silver, the joint is "cold" and will fail or not conduct signal well. You can "reflow" solder joints to get them shiny and add a quick touch of solder if needed. The joint must be held perfectly still until solder sets.

Practice on tinning wires and bits of junk metal before you try a real joint. you will get it quite quickly, less than ten attempts and you'll get satisfactory results.

 

[SGD Lutherie]

+1

I use a 60 watt soldering station, and set the temp for 700°F. I heat the part, flow some solder, and I'm out of there! Shouldn't take more then a second or so.