[Kenwood] Fw: MC-60 mike production error

[Walt Breining]

There is a serious problem with many Kenwood MC-60 or 60A microphones. The
correct wires to pin 1 and 7 ( shield and audio) are sometimes reversed in
the mike itself. One of the symptoms is distortion and RF pick up,
particularly when the stand is used.
How to tell if your mike has this problem:
While using the mike and hearing audio on transmit, with a temporary wire
ground the outside of the mike to the stand. Also try grounding it to the
radio. If in either case the audio stops (is shorted out) when the mike case
is grounded, you have this reversal problem.

When all is correct, Pin 1 is used for the hot mike audio and pin 7 is used
for the mike audio ground. (shield) Many of these mikes had pins 1 and 7
reversed internally. The best fix is to correct the wiring error in the mike
itself. However, getting the mike apart without doing damage is a challenge.
Work Around:
You can work around this by taking apart the plug that runs from the stand
to the mike and reversing pins 1 and 7. Everything will now be fine so long
as you use the stand. However, you still will have the problem if you use
the mike without the stand in line. As long as you always use the stand,
this is all that you have to do. It will work fine with or without the
pre-amp on.
If you wish to still be able to use this mike with or without the stand,
here is what is needed in addition to the above.
Reverse the wires between pins 1 and 7 on the male plug inside the mike
stand.
Then reverse the wires between pin 1 and 7 inside the 8 pin plug on the end
of the cord that plugs into the stand. If your radio uses the same plug, the
unmodified plug will have to always connect to the radio. The one you just
modified will always have to go to the stand. Mark the modified plug with
nail polish or by some means so you know which is which.
Now remember, if you can make the change inside the mike itself, or if your
mike is already OK, none of the above should be done.
In a correctly wired MC-60 system the shield grounds of the cables and the
ground inside the mike and the stand will go to pin 7. Pin 1 will be the
audio hot. (wire that is surrounded by the shield)
If you choose to do this work around modification to avoid disassembly of
the mike itself, the shields will all connect to pin 1 EXCEPT FOR THE PLUG
THAT PLUGS INTO THE RADIO.
The hot audio wire will be changed to pin 7 EXCEPT FOR THE PLUG THAT PLUGS
INTO THE RADIO.
If you always plan to use the stand modify just the plug that connects the
mike to the stand and forget the rest.
I tried to make this clear as possible. If you have any questions my e-mail
is n9wb at arrl.net.
Here is a link to the MC-60A schematic. It is correctly reflects the error.

ftp://80.162.141.166/manuals1/kenwood/MC-60A_Schematic@gt.pdf