Alto-SR400A-spk-sm 电路图 维修手册.pdf

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1、 Service Manual ALTO REV.2 Model: SR400A RadioFans.CN 收音机爱 好者资料库 CONTENTS 1.Specifications 2.Block Diagram 3.Schematic Diagram 4.Printed Circuit Board 5.Test Procedures 6.Structural Drawing 7.Exploded View when the output signal is 0.5Vpeak, the led must be GREEN lighted. -Then, rotate the volume po

2、tentiometer knob full clockwise Par. 4: BOOSTER check of LOW Amplifier - Connect alternatively the CH2 probe tip of scope on D2 cathode and D3 anode and verify the following conditions: when the output signal is 18Vrms the VCC1 voltage must follow the output signal wave with 4Vdc offset, as shown in

3、 the following picture TESTING PROCEDURE - Switch ON the LOW amplifier output to 4 load resistor and repeat the above booster check verifying more or less the same VCC1 conditions and verify that the signal must be symmetrical refer to GND, without detectable distortion and oscillation. Increase the

4、 VOLUME pot. until a signal clipping. Switch OFF the LOW amplifier out. to 4 load resistor Par. 5: COMPRESSOR check of LOW amplifier -Increase the input signal of 10 dB and check the out. signal to remain constant at 45Vpeak and if the Signal/Comp. led has changed the lighted colour, from GREEN to R

5、ED. Par. 6: PTC function check on Heatsink - Heat the PTC temperature sensor with a welder heated tip, in touch with its body, to verify this protection works properly reducing the amplifier out. signal to few volts on time. P.S. The check must be done with PTC, placed into heat-sink hole and silico

6、n grease on. Par. 7: Idle current setting of LOW amplifier - Decrease to zero the signal generator, then, adjust VR1 trimmer to have a 5mV 0,5mVdc voltage drop across R13 & R15 (0,22 ) power resistors. Par. 8: HIGH amplifier check . - Select a 10KHz frequency with 0dB amplitude on signal generator.

7、- Connect CH2 probe tip of scope on HIGH amplifier output. - Check that the high amplifier power output signal is 26+ 2VPEAK (18VRMS). - Switch ON the HIGH amplifier output to 8 load resistor and increase the VOLUME pot. - Verify the out. signal is limited to 22Vpeak. -Switch OFF the HIGH amplifier

8、output to 8 load resistor. Part .9: Burn-in test 1. Connect the pink noise signal from CD player with the line input of speaker module. 2. Connect 4ohm 500W load resistor with the bass output. 3. Connect 8ohm 300W load resistor with the treble output. 4. Put band switch to the position 1, and then t

9、urn on the power switch of speaker module. 5. Adjust the pink noise level from CD player untilSIGNAL/LIMIT indicators (red, green) sparkle. 6. Put the speaker module vertical and take the burn-in test for 2 hours. Part .10: Final inspection 1. Check the electronic performance of the tested unit completely. DSP OFF Frequency Response Curve of SR400A Speaker Module