Adcom-GFA7400-pwr-sm维修电路原理图.pdf

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1、SERVICE MANUAL 5 CHANNEL POWER AMPLIFIER GFA-7400 TABLE OF CONTENTS Introduction . . . . . . . . . . . . . . . . 1 Test Procedures . . . . . . . . . . . . . 1 Parts List . . . . . . . . . . . . . . . . . . 2 Specifications . . . . . . . . . . . . . . . 5 Schematic . . . . . . . . . . . . . . . . . 8

2、551 E. Anderson dr. Suite 105 Scottsdale,AZ 85525 USA Tel: 480-607-2277 Fax: 480-348-9876 RadioFans.CN 收音机爱 好者资料库 1 Web: INTRODUCTION This service manual is intended to assist trained and qualified technical personnel in verifying the performance of, adjusting, and repairing the ADCOM GFA-7500 ampli

3、fier. The procedures described here are not intended for persons unfamiliar with the appropriate safety and test procedures. TEST PROCEDURES All tests are performed with a 115V, low-distortion (less than 2% THD), AC-power source, 8-ohm resistive load (except slew rate), and a signal source of not mo

4、re than 600 ohms. An 80kHz low-pass filter is employed during THD distortion measurements. Signal-to-noise measurements are “A” weighted. Damping factor is measured by comparing the 1 watt output voltage with and without an 8 ohm load. Slew rate is measured with an inductive load, and is derived wit

5、h a dual-time-based oscilloscope reading the slope of a full power 5kHz square wave. DO NOT OPERATE THE AMPLIFIER AT FULL-POWER SINE WAVE ABOVE 22kHz OR FULL-POWER SQUARE WAVE ABOVE 5kHz. CORRECT BIAS ADJUSTMENT IS CRITICAL TO THE PERFORMANCE OF THIS AMPLIFIER. MAXIMUM OUTPUT POWER, MINIMUM THD AND

6、HEAT DISSIPATION ARE AFFECTED BY THE BIAS SETTING AND MUST BE CORRECT TO MAINTAIN THE SONIC QUALITY AND LONGEVITY OF THE AMPLIFIER. BIAS ALIGNMENT The component references are the same for all channels. Operate the amplifier without load or input connection for this adjustment. 1. Turn the amplifier

7、 on and allow to idle for 5 minutes. 2. Connect millivoltmeter across emitter resistor R36. Adjust bias pot R25 for a 10mV +/- 1mV reading. NOTE: The bias adjustment must be performed with the heatsink attached and the amplifier module installed in the chassis. The best way to perform the bias adjus

8、tment is by connecting one probe of millivoltmeter to emitter of Q15 (lowest pin) and connecting the other probe to the positive (red) speaker output. DC OFFSET CHECK 1. Connect a millivoltmeter across the speaker output terminals and confirm a reading of 0mV +/- 10mV. WARNING THERE ARE POTENTIALLY

9、LETHAL VOLTAGES WITHIN THE GFA-7400 AMPLIFIER WHICH WILL BE ACCESSIBLE ONCE ITS TOP COVER IS REMOVED. DO NOT ATTEMPT FAMILIARIZATION, INSPECTION, OR ANY PROCEDURE WHATSOEVER UNLESS YOU HAVE DISCONNECTED THE GFA-7400 FROM THE WALL AC OUTLET OR OTHER SOURCE OF AC POWER AND THE POWER- SUPPLY CAPACITORS

10、 ARE COMPLETELY DISCHARGED. THESE INSTRUCTIONS ARE PROVIDED FOR USE ONLY BY COMPETENT TECHNICAL PERSONNEL. DO NOT UNDERTAKE ANY SERVICE PROCEDURES IN THE GFA-7400 UNLESS YOU ARE TECHNICALLY QUALIFIED TO DO SO. IMPORTANT BEFORE PROCEEDING WITH ADJUSTMENTS, MAKE SURE AMPLIFIER IS AT ROOM TEMPERATURE.

11、RadioFans.CN 收音机爱 好者资料库 2 GFA-7400 SERVICE PARTS LIST AMPLIFIER MODULE PCB SCHEMATIC ADCOM PART NUMBER DESCRIPTION LOCATION BR2 16007000 BRIDGE RECTIFIER SBU8G C01 12001075 CAPACITOR POLY FILM 2.2uF 100V C02 12001390 CAPACITOR POLY FILM 330pF 100V C03 12005295 CAPACITOR ELEC 100uF 63V C04 12001400 C

12、APACITOR MYLAR FILM 1uF 100V C05 12001490 CAPACITOR SILVER MICA 33pF 100V C06 12001580 CAPACITOR POLY FILM 4.7nF 100V C07 12005090 CAPACITOR ELEC 10uF 25V C08 12005225 CAPACITOR ELEC 100uF 100V C09 12005225 CAPACITOR ELEC 100uF 100V C10 12001585 CAPACITOR POLY 270pF 100V C11 12001585 CAPACITOR POLY

13、270pF 100V C12 12005220 CAPACITOR ELEC 100uF 10V C13 12001555 CAPACITOR MYLAR 0.1uF 250V C15 12005090 CAPACITOR ELEC 10uF 25V C16 12002075 CAPACITOR POLY 0.01uF 100V C17 12005165 CAPACITOR ELEC 22uF 35V C18 12005455 CAPACITOR ELEC 10000uF 63WV C19 12005455 CAPACITOR ELEC 10000uF 63WV C20 12001085 CA

14、PACITOR MYLAR 0.22uF C21 12001085 CAPACITOR MYLAR 0.22uF D01-D04 16004148 DIODE 1N4148 D08,D09 16004004 DIODE 1N4004 D10-D12 16004148 DIODE 1N4148 D13 16003600 DIODE ZENER 3.6V F3 19009800 FUSE T6.3A F4 19009800 FUSE T6.3A J1 22006000 RCA INPUT JACK LED1 16001254 DISTORTION LED LTL1254 (YELLOW) LED2

15、 16001204 PROTECT LED LTL1204 (RED) Q01 33003381 TRANSISTOR 2SC3381 Q02 33000092 TRANSISTOR MPSA92 Q03 33000042 TRANSISTOR MPSA42 Q04 33000092 TRANSISTOR MPSA92 Q05 33000092 TRANSISTOR MPSA92 Q06 33000092 TRANSISTOR MPSA92 Q07 33001380 TRANSISTOR 2SA1380 Q08 33003502 TRANSISTOR 2SC3502F Q09 33001567

16、 TRANSISTOR 2SC1567 Q10 33004793 TRANSISTOR 2SC4793 Q11 33001837 TRANSISTOR 2SA1837 Q12 33003281 TRANSISTOR 2SC3281 Q13 33001302 TRANSISTOR 2SA1302 Q14 33003281 TRANSISTOR 2SC3281 Q15 33001302 TRANSISTOR 2SA1302 Q16 33000042 TRANSISTOR MPSA42 Q17 33000042 TRANSISTOR MPSA42 3 Q18 33000042 TRANSISTOR

17、MPSA42 SCHEMATIC ADCOM PART NUMBER DESCRIPTION LOCATION R01 27004050 RESISTOR 1K R02 27004135 RESISTOR 4.99K R03 27004135 RESISTOR 4.99K R04 27004500 RESISTOR 49.9K R05 27004050 RESISTOR 1K R06 27004610 RESISTOR 22.1 R07 27003420 RESISTOR 249 R08 27003425 RESISTOR 347 R09 27004610 RESISTOR 22.1 R10

18、27004135 RESISTOR 4.99K R11 27004310 RESISTOR 1.78K R12 27004500 RESISTOR 49.9K R13 27004135 RESISTOR 4.99K R14 27004091 RESISTOR 75K R15 27003420 RESISTOR 249 R16 27003190 RESISTOR 5.6K 1/2W R17 27004135 RESISTOR 4.99K R18 27004670 RESISTOR 100 R19 27004225 RESISTOR 475 R20 27004610 RESISTOR 37.4 R

19、21 27004610 RESISTOR 37.4 R22 27003415 RESISTOR 75 R23 27004260 RESISTOR 2.74K R24 27004050 RESISTOR 1K R26 27004145 RESISTOR 392 R27 27004145 RESISTOR 392 R28 27004170 RESISTOR 10 R29 27004085 RESISTOR 49.9 R30 27004085 RESISTOR 49.9 R31 27004170 RESISTOR 10 R32 27004420 RESISTOR 33.2 R33-R36 37006

20、055 RESISTOR .33 3W R37 27004070 RESISTOR 2.21K R38 27004120 RESISTOR 22.1K R39 27004420 RESISTOR 33.2 R40 27003200 RESISTOR 5.1 2W R41 27004200 RESISTOR 10K R42 27004070 RESISTOR 2.21K R43 27004630 RESISTOR 221K R44 27004070 RESISTOR 2.21K R45 27004135 RESISTOR 4.99K R46 27004120 RESISTOR 22.1K R47

21、 27003280 RESISTOR 8.2K 2W R48 27003280 RESISTOR 8.2K 2W TB1 32007000 THERMAL BREAKER TH2 31007400 THERMISTOR CL150 U1 21005550 IC LM555 VR29 35001500 BIAS POT 200 4 POWER SUPPLY PCB SCHEMATIC ADCOM PART NUMBER DESCRIPTION LOCATION C01 12005010 CAPACITOR ELEC 1000uF 25V C18 12001510 SPARK KILLER C02

22、 12005120 CAPACITOR ELEC 220uF 16V D1-D6 16004004 DIODE 1N4004 F1 19001200 MAIN FUSE 12A F2 19000100 STANDBY FUSE 1A K1 28007400 TURN-ON RELAY LED1 16001245 POWER LED LTL1204 (RED) Q1 33001300 TRANSISTOR MPSA13 R1 27003110 RESISTOR 1K 1W R2 27004270 RESISTOR 3.32K R3 27004200 RESISTOR 10K R4 2700427

23、0 RESISTOR 3.32K T1 24007402 STANDBY TRANSFORMER TH1 31005800 THERMISTOR CL100 U2 21007812 REGULATOR IC 7812 37007400 POWER SWITCH OTHERS SCHEMATIC ADCOM PART NUMBER DESCRIPTION LOCATION T2 24007401 MAIN TRANSFORMER 13005805 FOOT 13007401 FRONT PANEL 13007402 HEATSINK 11001155 POWER BUTTON 11001165

24、POWER BUTTON FRAME 13007400 TOP COVER 5 GFA-7400 SPECIFICATIONS Power Rating (To FTC Requirements) 100 watts continuous average power per channel into 8 ohms at any frequency between 20Hz to 20kHz with all channels driven at less than 0.075% THD 150 watts continuous average power per channel into 4

25、ohms at any frequency between 20Hz to 20kHz with all channels driven at less than 0.075% THD IM Distortion (SMPTE) 1 watt to 100 watts into 8 ohms. 0.075% 1 watt to 150 watts into 4 ohms. 0.075% IM Distortion (CCIF, Any Combination from 4kHz to 20kHz) 100 watts into 8 ohms. 0.025% 150 watts into 4 o

26、hms. 0.025% THD + Noise at 100 watts into 8 ohms (Typical) 20Hz. 0.0012% 1kHz. 0.0012% 10kHz. 0.02% 20kHz. 0.025% THD + Noise at 150 watts into 4 ohms (Typical) 20Hz. 0.025% 1kHz. 0.025% 10kHz. 0.035% 20kHz. 0.045% Frequency Response 1 Watt into 8 ohms (10Hz to 20kHz). +0, -0.25dB Power Bandwidth (-

27、3dB). 1.5Hz to 65kHz Dynamic Headroom into 4 ohms. 2.5 dB Signal to Noise Ratio, “A” Weighted (100 watts into 8 ohms). 110dB Gain. 29dB Input Sensitivity for 1 Watt. 0.1 volts for 100 Watts. 1.0 volts Input Impedance . 50k Damping Factor (20Hz to 20kHz). 400 Rise Time (5kHz, 90V, peak-to-peak square

28、 wave, 20% to 80%). 4.5S Power Consumption (Continuous, All Channels Driven) Quiescent. 96VA Maximum. 1440VA 100 watts into 8 ohms. 1165VA Power (Available in 230VAC on special order). 115VAC - 50/60Hz Chassis Dimensions. 5” (127mm) x 17” (432mm) x 14” (355.6mm) Maximum Dimensions. 5 3/4” (146mm) x 17” (432mm) x 15” (381mm) Weight. 42 lb. (19.1 kg) Weight, Packed . 48 lb. (22.8 kg)