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Guide:Modifying your Handsfree Headset and Basic Soldering

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As you may or may not have noticed, the stereo handsfree kits that our PDAs come with have seriously bad earphones. These tend to inflict earaches, headaches and aneurysms. So ID64 and a few others thought "why not swap the earphones for something better?"

This guide will show you how to do just that.

All it requires is a bit of patience, some basic soldering skills and your favourite pair of headphones (be warned, you will be cutting these up so if you dont want to wreck your $200 Shure E3Cs, I'd suggest using some iPod headphones or something similar)

WE ARE NOT RESPONSIBLE IF YOU SCREW SOMETHING UP WHILST FOLLOWING THIS GUIDE!

You will need:

A soldering iron. Any run-of-the-mill one will do. Maplins sells one for about 2 bucks that'll do the job. Avoid the higher wattage soldering irons unless you're experienced because higher wattages=more heat=potential to fry components. Typically a chisel tip or micro/cone tip is suitable for small electronics.

Some solder. I prefer to use flux core solder. Solder is a "wire" made with any of the following; lead, tin, silver, nickel, or a few other soft conductive metals. You will need paste flux or flux core solder. Flux is just a paste that helps the solder stick to what you are soldering. Some apply it to the component, some to the iron/solder.

Your PDA's wired handsfree kit

The headphones you want to use your PDA with

Now, let's get down to business.

1: Heat up your soldering iron and leave it.

2: Open the hands free mic by prying the case apart using a piece of thin, stiff, plastic (e.g a picnic knife or your fingernails). DO NOT USE METAL, as the case is pretty fragile and gouges easily.

3: Once you've opened the casing, turn the board over and write down what earphone wire colors go to what circuit points. (You need to know left, right and ground). Ground is L- and R-.

4: Time to use that soldering iron. Apply a little solder to the end, and wipe it off with some toilet paper-etc. This is to ensure that heat will transfer quickly. To remove the earphones, carefully place the tip of the iron on the little silver bubble holding one of the wires leading to the earpiece. It'll melt pretty fast so you need to GENTLY pull the wire off quickly to ensure you don't fry anything. Repeat for the rest of the earpiece wires but do them ONE AT A TIME!. Look below at the red wire soldered to the board for a better example (Thanks KRL!)

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Feel free at any time to wipe the tip of your iron to keep it clean. Dry or moist lint free cloth/towel, or a moist sponge, as most prefer. The flux will burn into black flecks that do nothing but make things difficult, and there is nothing like getting a blob of solder spanning 3 joints/traces/burning a chip-etc.......

5: Grab the new headphones you want to use and cut the wire at the length you want plus an inch (1-3cm) (this extra inch goes inside the mic unit).

REMEMBER to pull the stripped end through the ring of the microphone casing and tie a knot to prevent any stress on the soldering point when reassembled. This is very important. If you skip this step, you may need to resolder connections that are pulled loose by brute force. Use a drill or something similar to widen the ring if you need to.

6: Being careful not to strip the wires inside, use the wire stripper to peel back the outer jacket and reveal about an inch (about 1-3 cm ) of the wires inside. If the wires have a plastic jacket, strip off 1/4 inch (about 0.5cm) from each wire. If the wires are fibrous or look like they are painted with enamel, then you will need to burn off the enamel by holding a lighter or match to the end of the wire. Be careful here because the enamel burns quickly up the wire and may expose too much metal. Once the enamel has burned 1/4 inch (about 0.5cm) up the wire, blow it out.

7: Now you will need to "tin" the wires. Take the wire you just prepared and rub it with flux paste and solder (skip the paste if you're using flux core solder). Melt a bit of solder on the end of your iron, and drag the end of the wire you just prepared through it (individually), adding more solder if needed. Once the wire "soaks" up the solder, remove it. The end of the wire should now be silvered with solder and without lumps/bubbles of solder attached. Trim the end of the tinned wire down to about an 1/8 inch (1 mm) to keep things neat and clean.

CAUTION: Holding a soldering iron to a wire for too long when tinning CAN burn the wire up inside the jacket, so be as quick as possible.

You should now have a fully prepared set of new earphones and a breadboard ready to solder them to.

8:Take the tinned end of the wire you just prepared and place it on the appropriate silver dot that you desoldered the old headphone wire from (by appropriate, you will have to consult the drawing you made earlier, and use your best judgment; the wires are color coded for a reason. Left/Right/Ground). I usually use a solder buddy or hemostats to hold everything while I solder, or occasionally securing the iron and bringing the parts to/from the iron. With the tinned end on the silver dot, place the iron tip to the wire/dot and melt the solder.

DO NOT keep the iron to the wire/board too long, as you could burn up components, wires, or traces on the board. Also, one must be careful not to move the wire while the solder hardens, as this provides a poor joint/connection that could fall apart or attenuate sound. When this occurs it is known as a "cold solder joint" or "cold joint".

Once you're done attaching the other wires, re-assemble the mic and try it out!


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