Popping noise in Pioneer shelf audio system

Hello,

I have a Pioneer model XRP340M shelf system. Unit started a low humming in speakers at all volumes but other than that worked okay. We had a 1/2 hr. brown out one day when the unit was plugged in but not turned on. After that, (maybe coincidence?) the unit would not power up at all. I opened it up and replaced the fuses. Now it powers up and eveything works fine, but when you turn up the volume past about 1/4 total volume, it makes a constant snapping noise in the speakers. I noticed a burnt spot on the main board around a resistor and some diodes. I removed the resistor and checked it with my DVOM and I believe it is okay. It is hard to make out colors from being burned is why I'm not 100% sure. Any tips on fixing the board or where I could get a replacement would be greatly appreciated. Was a fairly high end unit when new that takes the flip out 6 disc magazines. I have another unit that takes the magazines and I like that setup so am willing to go to the trouble to fix it. Pioneer lists the board as out of stock (part# axq-1018) and $107. Thanks, Jeff