Tuesday, May 20, 2014

Soldering Optional Auxiliary Audio Out Jack

Thus far all the wiring connections on the RV-12 have been either connectorized or crimped … however, the optional Radio Shack 274-249 1/8" stereo jack for auxiliary audio out requires soldering.  The Van’s drawing shows the auxiliary audio out jack needing to have two 47K ohm resistors attached to the jack, one on the tip and one on the ring connections … this requires soldering. For those new to soldering, the rest of this post is intended to provide helpful tips to hopefully alleviate your fears and help you produce good quality solder joints. For the most part, soldering small electronic components and connectors does not require a huge soldering iron … this is one arena where bigger is not better … a 25 watt soldering iron is more than sufficient for these small parts. For the soldering of general purpose electronic components, I have always had good luck with the Weller SP-23 (25 watt) solder iron outfitted with a cone tip. The cone tip is versatile in that the very tip can be used to apply heat to a small component or the entire edge of the cone can be used to apply a lot of heat when soldering larger surface areas.
A vice grip is used to prevent the small jack from moving. The two 47K ohm resistors are ready to be soldered onto the 1/8" stereo jack’s tip and ring soldering lugs - note the heat shrink tubing ready to slide over the solder joints once the soldering is completed.

Soldering electronic components is easily accomplished if five basic steps are followed.

1.  Soldering iron tips need to be kept clean and tinned ... often. Tinning is the process of melting solder on the tip of the solder iron when it first heats up to create a thin coating of molten solder over the entire tip. This helps to quickly transfer the heat into the work and allows the solder to flow quickly. I can’t overstress the importance of having a freshly cleaned and tinned solder tip. Some use damp sponges to wipe the tip onto prior to applying the tinning this practice is good for long soldering sessions … but for small soldering jobs, I just wipe the tip with a paper towel, immediately re-tin the tip with solder, shake off the excess solder onto a paper towel and then quickly solder the work.

2.  I won’t go into solder formulations but all you need to know is DO NOT USE ACID BASED plumbing solder or paste fluxes or solid solders when soldering electronic components. When soldering electronic components, ONLY USE solders containing rosin cores … my preference, 22 gauge solder or smaller because I find large diameter solders can tend to let a lot of rosin run out of the center core at times before the solder melts and this can become annoying and problematic.

3.  Commit - get in – solder - get out … you do not want to overheat the items being soldered. One of the worst thing you can do is dabble the soldering iron … by that I mean don’t lift the soldering iron off the work then place it back on the work … so on and so forth. Commit - hold the soldering iron on the work, flow the solder in and get off the work. Dabbling creates solder blobs and often contributes to creating cold solder joints, typically characterized by a dull or powdery silver appearance … not good.

4.  If at all possible, try making a solid mechanical connection prior to soldering and try to prevent the item(s) being soldered from moving. In the example for this post, the jack was secured in a vice grip - the resistors's leads were tightly bent around the solder lugs on the stereo jack and the 20 gauge wire was tightly wrapped around the resistor’s lead prior to soldering. It is acceptable to LIGHTLY tin stranded wire to help it hold its shape when attaching it onto another item.

5.  Let the solder flow into the connection. Commit and place the freshly tinned tip of the soldering iron firmly onto the work with light steady pressure and immediately try to feed a little solder into the location where the soldering iron is touching the work to begin melting the solder. The molten solder will aid in quickly pulling the heat from the soldering iron into the work and once the flow begins, keep feeding the solder until the item is satisfactorily soldered (but not to the point you are creating a large blob of solder) then quickly remove the soldering iron from the work. Also, while the solder is flowing, by dragging the tip of the soldering iron across the work one can spread the solder on the work … helpful when trying to fill an eyelet or soldering a long wire splice. When soldering stranded wire, consider placing the tip of the soldering iron under the wire, then feed in a little solder and once the solder begins flowing, transition the solder so it feeds in from the top of the wire directly above the soldering iron tip … for long splices move the iron across the bottom of the wire while following and feeding in solder along the top of the wire.

As always when learning a new skill, try experimenting and become comfortable with your soldering iron by soldering few pieces of scrap wire together until you get the hang of it. By following the five tips above you should have yourself making quality solder joints with very little practice.
The heat shrink tubing slid over the solder joints on the stereo jack and shrunk. Next the 22 gauge wire is wrapped around the resistor lead and ready for soldering.

After the 47K ohm resistors were soldered onto the tip and ring terminals on the 1/8" stereo jack, the heat shrink tubing was slid over the solder joint and shrunk with a heat gun. Next a 22 gauge wire was wrapped around the leads from the resistors and soldered.
The 22 gauge wire is now soldered onto the resistor leads and ready for more heat shrink tubing.

Heat shrink tubing was slid up the wire to cover the entire exposed resistor lead that the 22 gauge wire was soldered onto. After the heat shrink tubing was shrunk onto the resistor leads, a larger diameter piece of heat shrink was slid over the resistors to cover the small amount of exposed resistor lead where the heat shrink was slid over the solder connections at the stereo jack terminals.
Heat shrink covering the 22 gauge wire solder connections on the resistor leads.
Completed stereo jack with 47K ohm resistors and the 22 gauge wire solder connections all covered with heat shrink tubing.

Blog viewers may be asking themselves why just one piece of heat shrink wasn’t used to cover each resistor entirely? It very well may have been OK to do so. However, I though the heat shrink tubing being used was rated at the typical shrink ratio of 2:1 so was not sure if a diameter large enough to slide over the bodies of the resistors would shrink down enough to make a tight connection around the resistor leads. As it turns out, I forgot the DOG Aviation purchasing department had procured some high-grade polyolefin heat shrink that has a shrink ratio of 3:1 … but doing it with three pieces made a nice tight encapsulation of the resistors.
Auxiliary audio out 1/8" stereo jack mounted on the right floor pan.