[Elecraft] K3 Rear Panel Microphone Jack Bias Voltage

[paul alexander]

I recently assembled my K3 and am having some trouble getting a
microphone to operate.  All of my station microphones are  Motorola
handheld microphones.  These are dynamic microphones which have a
built-in amplifier, to make them appear as carbon microphones.  As
such, they require bias voltage.

My first attempt was to connect the microphone via the rear panel
jack, using the following menu settings:
    Mic SEL
         rPL.bIAS
and
    MIc + LIn
         On

Under these settings, I get no bias voltage on the rear panel microphone jack.

When I set Mic SEL for FPL.bIAS, I get bias voltage on the front
panel, and a microphone connected to the front panel connection works
as expected.

FYI, the radio Serial Number is 2925 and the firmware is version 1.98,
MAR 31, 2009.

Is it not possible to get microphone bias voltage on the rear panel
connector?  Do I have something set up incorrectly?

Any suggestions would be appreciated.

Thank-you

Paul Alexander
wb9ipa