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ATT Constantly on


I have a sony CDX m9900 and for some reason the ATT function is constantly on stopping any sound coming through the system. I go into the menu and turn it off but still no sound is coming through.

Was working fine one day then suddenly this function came on.

Have a blew the internal amp by any chance ? and is this a possible fix.

or is it something so simple that im missing it ?

Thanks in advance.

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  • gaz_rover Nov 19, 2008

    Hi moj920

    Unfortunately thats not the problem, iv had a look today and and asuming the mute wire is pink as the others are all acounted for then all is fine in that area. =(

    All i can assume is that the internal amp has gone faulty and thats whats causing it. As the rest of the stereo works fine.

    Are these units repairable? as i paid a wacking £450 3 years ago and i think the headunit is a great peice of kit. when its working lol.




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First thing i would check m8 is the cellular mute wire that is behind the head unit coming out of the main radio loom plug if the wiring is bare on that wire and its touching the stereos metal body or the black earth wire then that will make the att will come on because it thinks its recieving a call off a car kit so it mutes the radio automatically !

hope that sorts your problem out ;)

Posted on Nov 19, 2008

  • moj920 Nov 21, 2008

    sad to hear that m8 it may be the amp at fault then but yeah theres loads of places that can repair them still if i remember right theres a good site on here or i know a lot of ppl who have used them on the car audio forums that say there service is second to none .

    i,m sure your radio is the sony rolldown model where the screen folds over there known for ribbon cable faults but that won,t be related to your problem anyway good luck on getting it all working again :)



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