Kenwood TK-3860, trouble connecting to race harness

1

Hi all,

I have a TK3860 which works great with the included KMC-35 mic, but I can’t get it to work with my car race harness. Specifically, the microphone doesn’t work. PTT and audio out work fine.

I have the service manual, and the pinout of the 8 pin ethernet jack on the front of the unit includes these wires:

MBL
SB (power from radio, not needed)
GND
PTT
ME (Microphone ground)
MIC
HOOK
DM

The car harness (PTT & mic portion) only connects to the PTT, ME, MIC wires, which seems like it should be fine, since PTT grounding to the ME terminal should work.

I created an ethernet fanout cable, and confirmed that I can’t get the mic to work even when i trigger PTT by connecting the PTT wire to the normal GND cable, and also confirmed that grounding the PTT to the ME cable will trigger transmit.

Is there something else the kenwood might require on the hook or DM wires maybe? Maybe something in the software to tell it what kind of mic I have? I haven’t logged into the radio to look deeper into the settings yet.

Thanks in advance for any advice!

2

I don’t know that exact Kenwood mic, but as you have no audio, but it goes into transmit, I suspect the mic also need voltage to supply a condenser element, not a dynamic. If you have the usual ground, PTT and single audio line, check to see if there’s one extra line that needs connecting. Over the years it’s been a separate 5v line, or 5v superimposed on the audio line, like laptops sometimes do to power a headset.

3

Thanks!

I only have three wires from the headset, which I assume are two wires to the microphone, and one for PTT (which would just be grounded to the mic ground). Googling, maybe I need to connect the radio output’s 5V source through a resistor into the mic line, possibly adding a cap as well. Is this what you mean by “superimposing the 5V”?

Thanks,
–Carey

4

Yep, with a condenser capsule in there it needs power to operate, the older dynamic ones use the same wiring basics, grand, audio and PTT, but don’t need power.

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