About the only help I might be able to offer is to check your speaker connections for a short circut somewhere (two bare wires touching each other).
If that doesn't fix it, your only other recourse is to find a skilled tech. There are no user servicable parts in these units any more. This ain't the old days where you can attempt a fix on your own by taking the tubes out and bringing 'em to Radio Shack to test 'em.
while working at future shop. i was setting up a HK receiver. and when i plugged it in the protect sign was on the front. " i didnt even have speaker wire hooked up yet" so i tried a different outlet and same thing. so i just packed it up as a defect and opened another and it worked fine.