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I've got a Kenwood MC-59 microphone, which started fraying around the place where the mic cable goes into the body. I thought I'd cut it off and put a new RJ-45 jack on it.

After cutting the cable, I discovered something completely unexpected. Although it looks as if the RJ-45 plug has 8 insulated connectors:

top view of jack with 8 wires connected

the cable itself has only 7 (plus a shield):

end of cable with 7 wires + shield

Has anyone ever repaired one of these cables before, and if so - what goes where? How did you do it?

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    $\begingroup$ first of all, make double sure you've not accidentally ripped one cable out when cutting the cable; the eight one has to appear from "somewhere". Other than that, in your top photo it looks like there's two black cables – it's not unreasonable to assume they carry the same ground. $\endgroup$ – Marcus Müller May 7 at 11:34
  • $\begingroup$ Is the top photo the original plug? It looks like there are two black wires. Perhaps one of them was black sleeving covering the shield. $\endgroup$ – Mike Waters May 7 at 15:20
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    $\begingroup$ I can verify that I didn't rip a cable out - I cut it with diagonal cutters. @MikeWaters suggestion of a black sleeve is intriguing, I'll check continuity between the shield and the connectors on the other side of the cable. $\endgroup$ – user3486184 May 8 at 20:53
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Here's how to repair a Kenwood MC-59 microphone cable (ships with the TM-V71a, probably the 710, and a few LMR radios as well).

First, if you didn’t know already, behind the rubber boot at the end of the Kenwood MC-59 mic cable is a regular RJ-45 jack:

Picture of MC-59 hand mic with the boot slid down, exposing the RJ-45 jack

Step 0. If you want to avoid all this, the cord is part Kenwood E30-7543-18 at PacParts.com. (They also carry Kenwood 881M59-7889-72, which might be the same, and is a lot cheaper.) Avoid the cables that sell for under $10 on eBay - they will work, but will sound awful. The Kenwood cable has a shield that covers the clock line. If your cable doesn't have that, you’ll get a terrible buzzing noise in your audio - as if cicadas have infested your mic.

If you want to repair the existing cable yourself, you’ll need:

  • 1/4 inch (6.35mm) heat shrink, about 2-3 inches (50-75mm)
  • a network cable to sacrifice
  • an EZ-RJ45 jack
  • two paper clips
  • soldering iron
  • diagonal cutters
  • RJ-45 crimpers
  • utility knife (if your crimper doesn’t have a cutter)

Step 1. I'll assume you're repairing the head because the mic cord is wearing where the bottom of the boot meets the wire. That's what happened with mine. First, pull the rubber boot down, then disconnect the RJ-45 jack from the mic head.

Step 2. If it's still attached, cut the RJ-45 jack off the cable with diagonal cutters.

Step 3. Trim about 1 inch (25 mm) of the remaining jacket. Carefully unweave the braid from the clock line (on mine it was the white wire), separate the copper braid from the cloth braid, and wind the copper braid into a wire. (Although my original RJ-45 jack had two black wires, they were not electrically connected.)

Closeup of cable, with shield twisted to form a wire.

Step 4. Very important: now is the time to pull the boot down as far as it will go, and put the heat shrink on the wire. I ended up wishing I'd made my heat shrink longer - it fits, but exposes the same weak spot the cable originally had. If I'd added an extra inch (25 mm) or so, I'd have a stronger cable, I think. You can slide the boot partway down the curly part of the cord if you need more room.

Closeup of heatshrink placed on the cable, but not yet shrunk

Step 5. Sacrifice the network cable and take out about 3 inches (75 mm) of one wire. (I used the white/brown, so I wouldn't confuse it with the other wires.) Strip the wire back on one end. Carefully tack-solder that end of it to the base of the copper braid. I tried not to solder the whole braid so I would have some flexibility.

Image of brown/white wire from network cable tack-soldered to base of braid

Step 6. Feed the individual wires through the EZ-RJ45 jack. Order here is important. On my jack, it was:

  • yellow
  • grey
  • white
  • originally black connected to the shield, now white and brown
  • blue
  • black
  • red
  • green

Leave the wires long to give you plenty of room to work.

Here's a face-on diagram of the jack:

View of jack from front of jack. Yellow is on the left, then grey, white, black/shield, blue, black, red, then green on the right.

Step 7. Adjust the EZ-RJ45 jack first so it's in position, then put the heat shrink where it needs to be. Slide the EZ-RJ45 jack so it no longer covers the heat shrink. Heat the heat shrink so it conforms to the wire. Slide the EZ-RJ45 jack back down over the heat shrink.

Heat shrink shrunk around cable, with EZ-RJ45 in position, not yet crimped

Step 8. Crimp the EZ-RJ45. I didn't have the official EZ-RJ45 crimper, so I used my RJ-45 crimper and then trimmed the wires off with a utility knife.

Picture of the crimper in action

Step 9. Check all the wires for continuity with the RJ-45 connector on the other end. I used an ohmmeter with a couple of sewing pins held by mini-grabber test leads as probes.

Picture of probes (mini-grabbers grabbing sewing pins)

Step 10. You're almost done! (If the boot weren't so tight, you'd be done. But it's tight, and unless you're careful, it will push the heat shrink out of shape as you slide it up.) Deform two paperclips and slide them between the wire and the boot, and use those to wedge the boot around the heatshrink.

Paperclips unfolded and placed between wire and boot

Note as you slide the boot up that it has an orientation. Make sure the cut in the molded boot matches the tab in the EZ-RJ45 jack.

Closeup of molded boot with cutout for RJ-45 tab

Connect the mic head to the EZ-RJ45 jack. Slide the boot up, and the repair is complete. The cable can now be reconnected to the radio.

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    $\begingroup$ Nice answer, but I think it would be more complete with a photo of an RJ-45 crimping tool. $\endgroup$ – Mike Waters May 11 at 20:19
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    $\begingroup$ Added, thanks for the suggestion $\endgroup$ – user3486184 May 13 at 5:19

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