noise from my rti10/harman kardon 8000

Parachoute
Parachoute Posts: 88
edited December 2012 in Troubleshooting
Hi guys,
Need help here. Yesterday, I noticed strange noise from my rti setup probably coming from my Harman kardon 8000. Description: pok pok pok at a regular interval: around 140 bbm (2 Hz). The noise increase when I turn up the volume of the receptor. It happens without any input. It comes only from the 2 front speaker outputs, the center and rear canals are clean.
Any help would be very much appreciated. I love my rti/hk set up.
Thanks
Martin