[MRCA] Carbon Mic Checking

[WA5CAB at cs.com]

Bill,

With the microphone connected to the transmitter the voltage across the 
carbon mic element should be in the vicinity of 2 to 3 volts.  The M51 element in 
the M52 microphone works with the RT-77/GRC-9 when the latter is running off of 
6 volts.  And the electrical characteristics of the M51 are substantially the 
same as those of the carbon element in the T-17 and the microphone elements 
in the TS-11, TS-13 and TS-15 Handsets, all of which work with 6-volt radios.

If the bias voltage across the mic element is close to 24 volts, then the 
element or one of its connections must be open or nearly so. and drawing little 
or no current.  Which would explain why it doesn't work.

In a message dated 8/6/2008 11:28:05 AM Central Daylight Time, 
ka8wtk at ohio.net writes: 
> Hi Robert,
> The resistors and caps in the RC filter for the mic supply voltage have been
> replaced. I don't remember the exact voltage on pin "C", but it was close to
> 24 volts.
> 
> Bill KA8WTK
> 

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480