Classe-M700-pwr-sm维修电路原理图.pdf

RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 Class Model M-700/S-700 Bias and Offset Adjustment Ensure that the amplifier is assembled and functioning properly. Disconnect all input and output connections. Power up the amplifier. Adjust the A.C. line voltage to 120V. For each channel: Bias Adjustment: Connect the common lead of your digital multimeter to the pad labeled P17. Measure the voltages on the NPN emitter pads labeled P4, P5, P6, P7, P15, P16. Measure the voltages on the PNP emitter pads (see diagrams). These 12 pads must be constantly monitored during the first hour after the amplifier has been turned on. The transistors are matched for gain and therefore should have similar emitter voltages. The difference between the absolute values of the voltages on each emitter pad should never be allowed to exceed 6mV. When the amplifier is cold, the measurements should be approximately 14mV 5mV. Use trimpot R13 to adjust the bias. Final adjustment for each channel: Adjust the bias so that the average of the six NPN emitter readings equals 22mV. Offset Adjustment: Connect the common lead of your digital multimeter to the pad labeled P17. Measure the voltage on pad P11. When the amp is cold, this measurement should be approximately 100mV. Use trimpot R4 to adjust the offset. Let the amp idle for 6 to 8 hours at a room temperature of 22 Celsius (72 Fahrenheit). The line voltage should be steady at 120V. The heatsinks will reach a final temperature of approximately 47 Celsius (117 Fahrenheit). Final adjustment for each channel: Adjust the offset so that it is between 0mV and +10mV. NOTE: There is some overshoot when making bias and offset adjustments. Turn the trimpots to 1 revolution at a time and let the amp settle for 15 to 20 minutes after each adjustment.