Did you provide the model number of your amp and did I miss that? Also your speakers, listening level info would be helpful. Lastly, did you do the very first thing you should do which is call McIntosh service/support? They're really helpful and know the product best.
McIntosh mono amp red light flashes after a couple hours
Everything starts off OK with amplifier and then after a couple hours of use the red light begins to flash on one side of amp and unit shuts down. It's really sad when this happens. happened a couple times in past couple days. one power tube area feels warmer.
Is this a function of a power tube overheating and in need of replacing? Tubes are about a year old and receive daily use.