hifi engine

MCS 3125 Receiver...Don't Laugh It's A Beast.

Better known as JC Penney's,hope someone might be able to help out.This is a monster weighing in at just under 60lbs.But turning up the volume past the 1/4 mark puts it into protective mode.
Not sure who it was made by Pioneer maybe NEC.
Any chance someone can help with a schemetic ??