If you have a replacement set of tubes, then replace all the tubes (if you don't... you should have a replacement set). Then take your regular set of tubes in to be tested.
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.