Those knockoff ICs are almost never good. Real NOS is hard to find.

I couldn't find the print on the receiver but the chip is only 30 WPC which means you can use a couple of LM3886s in it, just figure out how to remount, use the inverting and non-inverting, hook up the power and the speakers, and you need a resistor to the muting line. Get them clamped to the heatsink and you should be alright. I did that on a Mitsubishi X-11 system. I almost wanted to just put preamp outs on it and tell the guy to use an external amp but they put the tone controls in the output feedback so they would not work unless I got some OP AMPs and this was just a better solution. Just hook up the speakers and you are good to go.

Cook wants to rebend pins but what I did was to turn the upside down and simply wire the pins to the board where needed. That way the pinout doesn't even have to come close. Ad the LM3886 is a six wires solution, and one of those is the muting and only requires like a ten K resistor which can easily do both channels. Don't even entertain the idea of leaving the working channel in there. Too much PITA and for no good reason.