So grateful to have found this site and the knowledgeable and helpful members here. I have fixed one amp so far with your help. This one is going to be a bit more challenging. Here we have a very nice Pioneer that was working just fine and then all of a sudden one day when it was powered up it gave the AMP ERR on the display and then went into shutdown mode and wouldn't power back up. I tried to reset the error but got the same results which means it wasn't a fluke. Nothing obvious when I look at the board from the top side - no bulging caps or burnt diodes that are visible, but there is a lot to look at and I'm aware that defective components aren't always visible to the naked eye. I haven't gone any further yet (no disassembly) and have been studying the schematic in order to familiarize myself a bit before I start digging. Any tips or suggestions are certainly appreciated! Thanks in advance ..