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How to re-solder a circuit board

STM solder lead

In today’s world, anytime a switch or other electrical component goes bad, we just toss it in the trash and buy a new one. This applies to just about everything we use, including our cars; but when it comes to classic cars, more often than not, you can’t just replace every component. They simply are not being reproduced, or they are cost-prohibitive for the average guy, especially if the car is a driver.
Take this 1951 Mercury for example. The factory turn signal switch was in usable condition, but the original wiring was wasted. Considering that the factory used cloth-covered wire, this is a common issue with most 50s and older vehicles. The wiring is readily available; however unlike even slightly newer vehicles from the 1960s, this era requires de-soldering the wires from the switch and re-soldering the new ones in place. While soldering two wires together is a simple task most gearheads have done before, de-soldering may not be. Don’t fret, it is not complicated, and there is a really neat tool that makes it a whole lot easier–it is called a solder sucker.
No more complicated than a spring-actuated vacuum pump, the solder sucker is designed to remove old molten solder from a joint. While you could leave the old solder on the terminals, it usually gets in the way of installing the new wires. By removing the old stuff, you are left with a clean terminal ready for new solder.
This process also eliminates any contamination or cold-solder joints left over from the original install. With the old solder off, the new wires are installed and soldered into place. A recent customer brought this kit to Red Dirt Rodz for assembly. The entire process took about 20 minutes from start to finish.
1. This is the solder sucker; the brand is Soldapullt. You can find these at most hobby shops and electrical supply stores. It is operated by pressing the plunger to load the spring, then you click the button when the solder is molten and *pop*, it magically disappears. Eventually you have to open the tool to empty it out.

1. This is the solder sucker; the brand is Soldapullt. You can find these at most hobby shops and electrical supply stores. It is operated by pressing the plunger to load the spring, then you click the button when the solder is molten and *pop*, it magically disappears. Eventually you have to open the tool to empty it out.

 

2. Using a soldering pen, the old wire terminals on the switch were heated until the solder melted, then the de-soldering tool was used.

2. Using a soldering pen, the old wire terminals on the switch were heated until the solder melted, then the de-soldering tool was used.

 

3. Sometimes the old solder does not go all the way into the tool, and you are left with a little chunk. Just toss it in the garbage.

3. Sometimes the old solder does not go all the way into the tool, and you are left with a little chunk. Just toss it in the garbage.

 

4. Notice how clean the terminals are. If you simply pulled the wire out and left the old solder on the terminals, getting new wires into the terminals would be quite difficult.

4. Notice how clean the terminals are. If you simply pulled the wire out and left the old solder on the terminals, getting new wires into the terminals would be quite difficult.

 

5. The new kit comes with reproduction cloth-covered wires using the original coding. Each one was stripped about 1/8”. The longer wire (top green) requires a jumper, so we left it long.

5. The new kit comes with reproduction cloth-covered wires using the original coding. Each one was stripped about 1/8”. The longer wire (top green) requires a jumper, so we left it long.

 

6. Schematics are a must for this type of work and the kit comes with one. The color codes are simple: G is green, GO is green with Orange stripes, GW is Green with White Stripes (Seven Nation Army anyone?), etc. Not too complicated.

6. Schematics are a must for this type of work and the kit comes with one. The color codes are simple: G is green, GO is green with Orange stripes, GW is Green with White Stripes (Seven Nation Army anyone?), etc. Not too complicated.

 

7. The first wire is the Green with a jumper. This terminal is split, so no need to cut the wire, strip it in the middle.

7. The first wire is the Green with a jumper. This terminal is split, so no need to cut the wire, strip it in the middle.

 

8. From there, move up the switch. By starting at the bottom, you leave room to get the soldering tip into the terminal without touching the other wires.

8. From there, move up the switch. By starting at the bottom, you leave room to get the soldering tip into the terminal without touching the other wires.

 

9. A little heat, a little solder, all done. Don’t overheat the wire or the switch, just heat it up until the solder flows through the wire and then pull the pen away.

9. A little heat, a little solder, all done. Don’t overheat the wire or the switch, just heat it up until the solder flows through the wire and then pull the pen away.

 

10. All done and ready to be put back into service in the car.

10. All done and ready to be put back into service in the car.

Sources:

Soldapullt

 

About Jefferson Bryant (221 Articles)
A life-long gearhead, Street Tech Magazine founder and editor Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 5 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced. You can follow Jefferson on Facebook (Jefferson Bryant), Twitter (71Buickfreak), and YouTube (RedDirtRodz).

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