nokia6230 ringtone not working

i have nokia6230 handset.few days back its ringtone stopped working.i
checked thoroughly and find out that not only ringtone does not work when
some one call me but if i want to listen to ringtones myself even then it
doesnot give me sound of ringtones.
however when i connect my headset then i call listen to ringtones.i can send
and receive calls wothout any problem however using vibrator for alerting me
when there is a call.
i have checked the external speaker it is working fine when i put it in
another nokia 6230 handset.
can anybody tell me what could be the reason or faulty component in the
handset.
thanks
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kind regards,
shahid bashir