Don't switch the CLASS A button while the amp is working and this will create issues on the circuit. Power off, then switch it, then only CLASS A mode is working which meant In class A biasing, the collector voltage is kept at approximately half the supply voltage, however, this means that the transistor is permanently passing collector current, even when no signal is applied, so power is being wasted, and although class A provides for very low distortion
I've had this amplifier since 1992/3. probably the worst purchase of my life. I took it dozens of times to technicians and there was never a cure... always with several problems... Marantz never again...
