# Splicing tiny wire inside broken mouse cable

I don't know a lot about electronics repairs, but I've got a relatively expensive laser mouse that got a frayed connection on the wire:

I'm wanting to repair it as it's out of warranty. I've cut the cable on either side of the "stopper", isolated each of the individual wires, and stripped the ends off in preparation for splicing.

Stripped http://img163.imageshack.us/img163/196/dsc2886c.jpg

I've read some instructions that indicate I should do an inline wrap and then apply some solder.

Is there a better way for wires this small?

Is there a particular type of heat shrink wrap I should put on this after it's spliced? Or will electrical tape suffice?

Inside the mouse, the cable is connected to a little plug. To me, it looks a lot like the fan plugs inside a PC. It's got 5 pins each 1mm apart. If there were a replacement plug I could buy and crimp the wires into, that'd be great!

http://img171.imageshack.us/img171/5205/dsc2893d.jpg

• @LeonHeller Soldering questions seem on-topic to me – Kellenjb Dec 15 '11 at 18:00
• Seems on topic to me. – Rocketmagnet Dec 15 '11 at 18:01
• @LeonHeller - when the task is the same as it could be for a modification or a one-off-scratchbuild, there's no need to worry so much about how the situation came about. – Chris Stratton Dec 15 '11 at 18:49
• Finally someone who knows what "focus" means and posted pictures at the appropriate size for the detail they convey! – Olin Lathrop Dec 15 '11 at 19:48
• Its a logitech, you can get a cheaper mouse of the same brand, and they all have the same connector inside – Journeyman Geek Dec 16 '11 at 10:15

I disagree with Chris in that you don't just want to shorten the cable. It's not the length of cable I'm worried about, but that tiny connector you don't want to replicate. The connector and the wires immediately coming out of it look to be intact. Replacing that will be a major pain in the butt, so I'd go to reasonable length to preserve that piece.

Since that piece is now short, you'll have to make a splice. Just realize up front you're not going to make a splice in such small cable that is anything like the size of the cable. The splice will be big, fat, and ugly in comparison. It looks like it can be made to serve as the strain relief too, so that helps a little.

To splice such tiny wires, see if you can sortof stick the stranded ends into each other. That may take some persuasion under a magnifying light, and then some weighty objects on your bench to hold them in place while you solder. This won't be easy, but it should be doable. If that just isn't practical, give up and bend each wire into a U and hook the two U ends together, flatten them together with a needlenose, then solder.

Once you have the connections made, wrap each one individually in a small piece of electrical tape, then wrap the whole bundle in electrical tape so that is looks like one fat section of cable. Like I said, big, fat, and ugly, but it should work. All that tape will act like a strain relief, so that section shouldn't break again.

• "Replacing that will be a major pain in the butt"... Very true! – Kellenjb Dec 15 '11 at 20:04
• Thanks - great advice! I'm going to give it a go after I've got the 3rd hand on Monday. And I'll see if I can find some wires to practice on first. It'll be nice to salvage this $70 mouse - it is sad that I have 3 or 4$15 mice that have never had this problem. – James Kolpack Dec 16 '11 at 1:39
• @James: Ah, so the real problem is you payed too much for a mouse. Sounds like you got $10 of mouse and$60 of marketing. – Olin Lathrop Dec 16 '11 at 13:03
• @OlinLathrop ha! Yes, that is likely close to the truth. It is a good mouse though - I like the precision of the laser, as well as being able to use it on other surfaces, and the scrollwheel is better than other mice I've used. I hate to throw away fix-able items, so I may have been doing this same routine with a \$10 mouse - also this one was Christmas gift a number of years ago, so no actual financial burden on my end :) – James Kolpack Dec 16 '11 at 14:15
• I ended up using the "stick stranded ends together and solder" method. This worked with minimum headache using the 3rd hand. After some trial and error, I was able to reassemble the mouse back together. Unfortunately the added fatness of the wires, and how they sit directly under the right mouse button, make that button sluggish to click in comparison. I tried rearranging the wires a few times but it never got back to the original state. But at least it works now! – James Kolpack Dec 21 '11 at 1:45

As neat multi-wire splices are hard to make, I'd recommend that instead of splicing, you simply shorten the cable by discarding the inside piece and connect the outside end to the circuitry inside. Try to replicate the function of the strain relief somehow.

• That's a good thought on reconnecting the wire inside the mouse. It's connected to a little plug - I've added a picture to the original question. The plug is like one of those in a PC that powers a case fan, except with 5 pins each separated by 1mm. I don't see any brand or identification markings on it. Would it be possible to get a replacement, or reuse it somehow? – James Kolpack Dec 15 '11 at 18:41
• Doing a splice inside the mouse and replacement strain relief where you have plenty of room to treat each wire separately would not be so bad. Soldering the bare wires to the pcb at the connector's pins might be another option - looks like you might have room to do that without removing the connector. – Chris Stratton Dec 15 '11 at 18:47
• Ok - yes, I was going to do the splice inside the mouse and then add strain relief. My real trouble is that these wires are so very small - it'll be difficult to wrap and solder them I'm thinking. I've ordered a "3rd hand" - perhaps that will make it possible. For the strain relief, I'm planning to epoxy the cable into the "stopper" - it's already a snug fit and I hope that the glue will make it pretty robust. – James Kolpack Dec 15 '11 at 18:59
• You should be able to twist and solder arbitrarily small wires with practice. Heat shrink tubing can be nice for protecting the joints, but be careful not to melt the mouse with the hot air! Personally I'd probably solder to the PCB at the connector, by adding extra solder to the pins and pre-tinning the stripped wires (at least the PCB won't run away from you) and then maybe glue the cable to the PCB nearby. – Chris Stratton Dec 15 '11 at 19:25

Has anyone tried using a metal sleeve and slipping the wire inside then applying heat to the sleeve? Solder will be drawn in like sweating copper pipe. The result should be a strong, straight connection, No larger than the diameter of the copper sleeve. You can even MAKE your own conducting glue from 1/2 graphite and 1/2 rubber glue and skip the solder.