Схема и документация усилителя Other GM TWIN 10, TWIN 14

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BIAS ADJUSTMENT
Instruments, materials and tools:- Audio Generator- Dual Trace Oscilloscope (earth ground floating)- Digital Voltmeter (or Multimeter)- 2x4E 220W Resistor- Temperature MeterSetup:- Connect the audio generator to the input (CN1) and set its output at 1kHz sinusoidal signal.- Insert the temperature snsor through the interstize between the heatsink and R119 (PTC).- Connect the 4E 250W resistor to the amplifier outputs- Connect the oscilloscope probes (setting 20V/div.,1ms/div) on th loads.- Insert the voltmeter terminals on R146.- Turn VR1 and VR4 clockwise up to end-stroke
ADJUSTEMENT PROCEDURE1) Turn on the amplifier.2) Set the input signal to 0dB (0.775Vrms).3) When the temperature has reaches about 50°C (121°F) set the signal input to minimum (0 or -
4) Adjust the trimmer VR3 to read a voltage of 15mV±0.05 on the multimeter.5) Check that the voltage across the R144 resistor has the same value.6) At ssame temperature condiction, adjust the VR2 trimmer to read 15mV±0.05 across R130 resistor.7) Check that the voltage on the R143 resistor has the same value.
Verifing:- Increase the input level to obtain an output voltage about of 0.5Vpp.- Check with the oscilloscope that the output signal is without a cross-talk distortion and eventually slightly adjust the VR3 or VR2 position until distortion disappears.- The voltage value across the R130, R143, R144, R146 resistors must not exceed 18mV.