Possible problem will be on the speaker relay ckt. as discussed in onkyo's service bulletin.
"When the speaker relays are activated, the collector of Q231 and Q232 should drop to near 0Vdc. Voltage can be monitored at terminal P6830 and P6832. Q231 supports RL6600, RL6602 and RL6603, where as Q232 supports RL6605 for Zone 2 operation. If the DVC at P6830 collector or its follower terminal is HIGH, it should be an open transistor Q231."
Usually answered in minutes!