Rob, I have some personal experience with Onkyo receivers, but I don't use separate amplifiers and I've never really given much thought before about triggering one on. You don't give much detail beyond "is not working" (specifically what did you try?), but I assume you mean that Yamaha did trigger it on.
I took a look at the 808 manual and saw that there are trigger outs for Zone 2 and 3, but not specifically for the main room and there didn't appear to be any instructions(surprise)as to how to do it. Looking at pp. 70-73, it does indicate that when Zone 2 or 3 are turned on that the triggers are activated with 12v. It would seem that if Zone 2 or 3 was turned on with the remote, as indicated, and perhaps a source for it selected, that(despite the lack of any Zone 2 or 3 speakers)the XPA-3, if properly connected to the trigger out, would likewise turn on with the "phantom" Zone.
