Схема и документация усилителя Other GENERALMUSIC LPS-10, LPS-12, LPS-MON

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BIAS ADJUSTMENT - LPS 12 ACTIVE / LPS MONITOR ACTIVEInstruments, materials and tools:- Audio Generator- Dual Trace Oscilloscope- Digital Voltmeter (or Multimeter)- 4E 200W Resistor- Temperature MeterSetup:- Remove the Power Amplfier Board from the chassis keeping in connections with transformer and diode bridge;- turn VR1 clockwise up to end-stroke;- connect the audio generator to the input and set it to output 1KHz sinusoidal signal;- put the volume potentiometer at its maximum level;- connect the 4E 200W resistor to the amplifier output instead of the speaker;- connect the oscilloscope probe on the load (setting 20V/div., 1ms/div);- insert the temperature sensor through the interstice between the heat-sink and R59 (PTC);- insert the voltmeter terminals across R60.Adjustement Procedure1) Turn on the amplifier.2) Set the input signal to obtain 0dB (0.775Vms).3) When the temperature has reaches about 50°C set the signal input to minimum (0 or -
4) Adjust the trimmerVR1 to read a voltage of 10mV ±0.05mV on the multimeter.5) Check that the voltage across the R61 resistor has the same value.Veryfing:1) Increase the input level to obtain an output voltage about of 0.5Vpp.2) Check with the oscilloscope that the output signal is without a cross-talk distortion and eventually slightly adjust the VR1 position until distortion disappears.3) The voltage value across the R60 and R61 resistors must not exeed 15mV.4) Re-connect the speaker instead of the 4E 200W resistor.