Open the amplifier and check the track that goes next to the throttle. Sometimes it happens that the power voltage breaks down on the track that runs next to the high voltage line. Knocks out the resistor and the operational amplifier tl072. If you don’t figure it out, write, I’ll tell you.
This is provided if the amplifier works, if not, then the problem is in the output transistors. There are IRGP4072d