The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

PC Board # EPT690010D

EL Driver PC Board # EPT91V131Z


Radio has buzz on transmit caused by the high voltage unit that lights the face plate. Buzz goes away if I turn off lights, buzz gets worse if I just unplug the face. The buzz sounds almost like alternator whine.

I can slightly reduce it by placing a .2uf Cap from mic input to ground, but it is not enough and it also lowers the tone of the voice, so that won't work.

Is there a fix for this issue? Any suggestions?

EDIT: Moving the mic wire around in different positions does reduce noise somewhat, I removed all un-necessary length from this wire also. I also found that moving the wiring harness around makes a difference also. There has to be a way to reduce the noise being radiated from the face driver, the circuit is shielded in a metal case. I did try and ground the metal case and the noise magnified ten fold.

I wonder if placing ferrite beads on the mic wire will help, I know I have a few somewhere, I just have to do some digging.

Try This Timrim
http://www.cbtricks.com/cgi-bin/databas ... s=1&key=72

Sorry Timrim,Try this,the previous one aint gonna work.
http://www.cbtricks.com/cqi-bin/databas ... s=1&key=72

Wrong again,Sorry
http://www.cbtricks.com/cgi-bin/databas ... s=1&key=72

Thanks Ramblingman. Noise on transmit is now reduced to the point that it is acceptable. Routing the wiring harness was a major factor in fixing this, as well as shortening the mic wire from the jack to the echo board.