Have noticed that on 626 when listening to FM radio signasl in the "FM-Auto" selector position which is the "stereo" position, reception is noisy. Signal is very strong as displayed on signal strength needle meter. Have noticed when I rotate selector knob to Mono listening position (for FM) the "noise" disappears. Maybe time for a service run? Any thoughts. All other sources that are sent from receiver (turntable, cassette, CD player) "noise" free. Thanks in advance for any input.