Fw: [Kenwood] MC-60A RF Simpfilied

[Walt Breining]

After looking at this closer, there is a simpler method to correct this
problem, although it is less complete.
If you are experiencing RF problems with a MC-60 microphone when the stand
is in use, try changing the following wires in the plug that plugs into the
mike as described below.  This will avoid taking the mike apart.

Dissemble the plug on the cord from the stand to the mike that plugs into
the mike.  Be sure that you do not loose the screws. Place the shield wire
on pin 1.  Place the hot audio wire that is surrounded by the shield to pin
7.  Using the base, see if the RF problem is corrected.

If this does not improve the RF problem return the wires to their original
position.  Your mike is probably not one of the reversed ones.

If it does solve the problem Please note:

The reversal issue will still occur with the mike connected without the
base, but this will correct it with the base in use and avoid dissembling
the microphone itself.

Vy 73, Walt N9WB


----- Original Message ----- 
From: Walter A. Breining
To: KenwoodMics at yahoogroups.com
Sent: Sunday, April 10, 2005 6:59 AM
Subject: [KenwoodMics] RF with MC-60 A microphone

There is an error in the diagram.  Is there an error in the mikes?
this would account as to why many are having problems with these
mikes.

I see a clue here.
(> Mike hooked directly to rig (MC-60A base bypassed) worked OK.

I do not have an MC-60A but I became curious when I heard that several
people were having problems with these mikes picking up RF when the
base was
used.  So I downloaded the Schematic.

Please note, that this diagram has the audio and shield leads (pin 1
and 7)
on the mike itself reversed.

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

Unless I have been working too late again I found the following:

On the microphone pin 1 is the Mike ground.  Pin 7 is the mike hot
audio.
But on the cord, the shield is connected to pin 7 and the yellow wire
that
is surrounded by the shield is connected to pin 1  On the stand, pin
1 is
the hot audio in and out whether or not the preamp is in or out. Pin
7 is
used as the audio and stand ground.

So it there an error in just the diagram, or were some mikes wired
this way
and maybe even incorrectly wired in the cord or base to correct for
this?
We recently ran into a problem with a Yaesu where the diagram and
some of
the radios both had incorrectly wired phone jacks

If some of the mikes were actually Mis-wired this way, so the hot
audio wire
went to pin 7 and the mike ground that attached to the mike case went
to pin
1,  This certainly would cause an RF problem that would be worsened
when the
stand was used.

You should check the inside of the stand and see that the stand
ground goes
to pin 7 on the stand male and female.  Also check the cable to be
sure that
the shield connects to pin 7 on each end.

If you can get the plug apart on the mike, you can check to be sure
that the
mike case, the mike element ground, and the transformer common wires
all
connect together electrically and connect to pin 7 on the mike.  The
transformer common wires will be the wires that do NOT go to the Hi
Low
impedance switch.

If you cannot get the plug apart from the mike, there is another way
you can
check if you can get to the element.  Before you use an ohm meter on
the
mike note you can magnetize the transformer.  To do an ohm check on
the
mike, you must disconnect the hot mike element wire from the impedance
switch and place the switch in 500 (Low) Pin 7 should show continuity
to
mike case ground.  Pin 1 should show continuity to the switch
terminal where
the hot element wire was removed with the switch still in low.  There
should
be no continuity between pins 1 or 7 or pins 1 or 2 when the cord is
not
plugged into the mike.

If you are using a cord with a 6 pin plug on one end, Pin 7 on the 8
wire
plug is connected to the center pin 6 of the 6 wire plug by the
shield wire.

If you are using a cord with a 4 pin plug on one end, Pin 7 on the 8
wire
plug is connected to pin 4 of the 4 pin plug by the shield wire.

vy 73, Walt N9WB