[MRCA] Carbon Mic Checking

[Bill Ramsey]

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

-----Original Message-----
From: mrca-bounces at mailman.qth.net [mailto:mrca-bounces at mailman.qth.net] On
Behalf Of WA5CAB at cs.com
Sent: Wednesday, August 06, 2008 11:17 AM
To: mrca at mailman.qth.net
Subject: Re: [MRCA] Carbon Mic Checking

Bill,

One thing you should check before scrapping the element is the mic element 
bias supply.  Odds are probably against it but you could have an open or 
seriously changed in value resistor(s) there.

In a message dated 8/5/2008 6:26:30 PM Central Daylight Time,
ka8wtk at ohio.net 
writes: 
> Hello All,
>   BANG! BANG! BANG! (Sound of beating mic on table) No change.
>   Modulation control is up all the way, clipping down all the way and line
> level up all the way. No joy. I got out the old analog meter to check the
> element, shows about 1K static. There is almost no deflection when yelling
> into the element. Fed some audio into the rig from a small audio amplifier
> and the unit modulates. Looks like I probably have a bad element. (Agree?)
>   I have heard of ways to get old telephone carbon buttons working again,
> but I can't remember if it involved baking them or freezing them. It is
> probably easier to just get another element and try it.
> 
> Bill KA8WTK
> 

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