Indeed. I just fixed an SE/30 with the same symptoms with a little isopropyl alcohol and some cotton swabs to rub away any oil, corrosion, or whatever may be on the board. On the Classic II, I believe the sound chip is integrated with the EAGLE gate array, so look for the big VLSI chip on the board. Failing that, or in case the entire board is pretty bad and you don't want to rub everything, the dishwasher treatment should work fine -- just be sure to remove the RAM first.