Phil Allison wrote:
David Farber wrote:



** So no RF OR maybe the frequency is off.

Do you have a frequency counter that works at UHF ?

If so, use that to see if there is a carrier and at what frequency -
just hold the mic right next to a short antenna plugged into the
input.



The mute switch on the mic seems a little wonky. There is a lot
resistance (physical) moving it to the mute position and almost no
resistance moving it back to the "on" position. Does enabling the
mute switch turn off the RF?


** No, it just mutes the audio.

Last one of these beasts I saw had a problem with the frequency
synthesiser
inside the mic handle. It was outputting a carrier frequency the
receiver did not work on. Off by only 100kHz from one of the
available ones, but that was enough - plus the buttons on the mic
did nothing to change that frequency.

The local Shure agents supplied a new mic at trade price to my
customer, cos that had no way to fix it either.


I have a frequency counter... a Heathkit I built around 1982 I
believe its upper range is 30MHz.


** No use at all.


I was thinking if I could open up the transmitter,
maybe there was some minor physical damaged caused by some rough
handling around the mute switch area.

** The mute switch doe not stop RF.

Getting back to the disassembly question, can I
just unscrew the mic capsule? I don't want to force it but if it's
ok to safely remove it that way, then I'd like to get to the
internal circuitry.


** The head should unscrew easily, then the C-clip as previously
stated.

Be CAREFULL, the buttons that operate the switches are FRAGILE.

BTW:

Do you know the mic's frequency ??

The handbook gives tables for code letters and actual frequencies.

Do you have a radio scanner that covers the UHF band ??

You MUST have a counter or a radio scanner or you cannot service
radio mics.



.... Phil

I do have a scanner. It's a Bearcat BC125AT. It will receive analog only. I
do no plan on making a habit out of servicing radio mics but this is for a
charity.

There is a label near the battery that says, 623.350 MHz FM. According to my
scanner's user manual the upper limit of the UHF band is 512 MHz. I'm
guessing that's not going to work.

Thanks for your reply.
--
David Farber
Los Osos, CA