[Boatanchors] D-104 mic

[Richard Knoppow]

----- Original Message ----- 
From: <telegrapher at q.com>
To: <boatanchors at mailman.qth.net>
Sent: Monday, July 18, 2011 12:50 PM
Subject: Re: [Boatanchors] D-104 mic


>I feel i have determined that two of the heads are bad.  I 
>have a 3rd D-104 that i use with my TCM equipment and 
>supplies plenty of drive for it.  Apparently it sounds good 
>also as i've had extremely good signal reports, audio 
>quality wise.  I swapped the heads around and found two of 
>them that were putting out nothing.  Even the old VOM and 
>listen for a click routine showed no results.  they both 
>measure wide open and that apparently from what i have been 
>told is correct.  The wiring from the heads clear into the 
>radio thru the G stands checks out with no grounds nor 
>opens.  I ahve ordered three (3) of the Kobitone elements 
>from Mouser.  The third of course is in the event the now 
>working mic goes belly up.
>
    Look at the schematic to find which contacts on the 
bottom of the mic go to the element. Check it with an plain 
ohm meter. A good element will measure open circuit but make 
an audible click when the meter is connected and 
disconnected. A bad mic may also measure open circuit but 
will not click. A bad mic may measure some value of 
resistance, typically around 100K. Crystal mics can go dead 
but can also become degraded where the output level drops 
significantly and the frequency response is affected.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com