Jvc rx-d301 lfe audio issue

Dear Freind,
i have JVC RX D 301 AV RECEIVER. Somedays before i got problem and i gave it for repairing...now after repairing LFE AUDIO NOT COMMING...
what are the causes...kindly let me know... and suggest good tecnician for repairing..
Regards,
sunil mo 9909981812