General_Music_LEM_P300_Service_Manual电路图.pdf

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1、1 1 1 1 1 J J J J J CODE : 277318 Index one positive and one negative low rail (+/-Vcc1) and one positive and one negative high rail (+/-Vcc2). Visual CheckVisual CheckVisual CheckVisual CheckVisual Check Use compressed air to clear dust in the amplifier chassis. Before proceed to supply the amplifi

2、er check visually the internal assem- bly, if appears an evident damage find the most possible reasons that cause it. Check the wiring cables for possible interruptions or shorts. If the damage has burnt a printed circuit board dont try to repair it, replace with a new one. Test InstrumentsTest Inst

3、rumentsTest InstrumentsTest InstrumentsTest Instruments Audio Generator Dual Trace Oscilloscope Digital Multimeter 4 500W, 8 300W, 100 10W resistors Variac (0250Vac) SetupSetupSetupSetupSetup Connect the Variac between the mains and the amplifier and set it at zero voltage. Set the amplifier in STER

4、EO MODE and turn full clockwise the LEVEL potentiometers. Connect the audio generator to the channel inputs and set it to 1KHz 775mVRMS (0dB) sinusoidal signal. The procedures that follow must be executed subsequently in the order specified. Supply CheckSupply CheckSupply CheckSupply CheckSupply Che

5、ck Remove the transformer secondary fuses (located on SUPPLY & PRO- TECTIONS board), set the Variac to the nominal mains voltage, check with the Multimeter the AC supply voltages: F1-F2=521.5Vac F3-F4=883Vac. Re-set the Variac at zero voltage, turn off the amplifier and put the fuses back on its hol

6、ders. Connect the oscilloscope probes CH1/2 to the channel outputs, before RL1, set both to 20V/div. 200S/div. Set up the Variac slowly monitoring the Outputs with the oscilloscope CH1/2 connected, it should display the sinusoidal input signal amplified with no distortions, if a distortion occur che

7、ck the POWER AMPLIFIER boards as suggested in the ADVICES section. If the protection trips, turn off the amplifier, wait some minutes and disconnect the supplies from the outputs modules (CN1, CN4 on POWER AMPLIFIER boards), continue to check the supplies. CAUTION: Before re-connecting the output mo

8、dules to the supplies,CAUTION: Before re-connecting the output modules to the supplies,CAUTION: Before re-connecting the output modules to the supplies,CAUTION: Before re-connecting the output modules to the supplies,CAUTION: Before re-connecting the output modules to the supplies, you must have the

9、 capacitors discharged for your safety: connect ayou must have the capacitors discharged for your safety: connect ayou must have the capacitors discharged for your safety: connect ayou must have the capacitors discharged for your safety: connect ayou must have the capacitors discharged for your safe

10、ty: connect a 100100100100100 10W resistor across the caps and remove the resistor just after 10W resistor across the caps and remove the resistor just after 10W resistor across the caps and remove the resistor just after 10W resistor across the caps and remove the resistor just after 10W resistor a

11、cross the caps and remove the resistor just after they are discharged.they are discharged.they are discharged.they are discharged.they are discharged. Finally verify the DC supplies on POWER SUPPLIES board: CN1 pin 1-2 (+Vcc2)=+612Vdc CN1 pin 3-4 (+Vcc1)=+361.5Vdc CN2 pin 1-2 (-Vcc1)=-361.5Vdc CN2 p

12、in 3-4 (-Vcc2)=-612Vdc CN3 pin 3-4-5=+151Vdc CN3 pin 7-9-10=-151Vdc If one or more voltages dont correspond, check the rectifiers, capacitors and transformers disconnecting them from circuitry, refer to schematics. Channels CheckChannels CheckChannels CheckChannels CheckChannels Check The channel A

13、is on the right and channel B is on the left of the chassis. These procedures are intended for one channel at a time, repeat these operation for the other channel. Verify, with the Multimeter, the insulation between the heatsink and the transistors collectors. Verify, with the Multimeter, the PTC re

14、sistor value (R33 connected across pin 8 an pin 9 of CN3), it must be between 50 and 200. SETUP:SETUP:SETUP:SETUP:SETUP: Connect the CH1 scope GND clip to CN2 pin 1 (GND terminal). Connect the CH1 probe tip to CN2 pin 2 (AMP output). Connect the CH2 probe tip to D9 anode and set it sensitivity at 5V

15、/div. Set the LEVEL potentiometers full clockwise. The load resistor is disconnected. INITIAL TEST:INITIAL TEST:INITIAL TEST:INITIAL TEST:INITIAL TEST: Increase slowly the Variac. The channel output signals must be symmetri- cal respect the GND without visible distortion and oscillation as shown in

16、Fig.1 Trace A (Trace B shown the amplifier 2nd stage input). If there is a distortion read the section ADVICES and proceed to check the other channel. BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT: Set the generator level at zero, connect the Multimeter across the e

17、mitter and collector of TR8, then adjust R32 trimmer to read 2.5Vdc. Set the CH2 scope sensitivity at 0.1V/div. and adjust the R35 trimmer to set the CH2 trace at the centre of the scope screen. HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK: Connect the CH2 probe ti

18、p to D3 cathode and set it sensitivity at 20V/div. When the output signal (Positive half-wave) is less than 30Vp the voltage on D3 cathode must remain constant at 36V, when the output signal exceeds 30Vp the voltage must follow the output signal with 6V offset (see Fig.2 Trace B), to check the negat

19、ive high rail connect the probe to D14 anode (see Fig.2 Trace C). Connect the 8 300W load on the output and repeat the INITIAL and HIGH RAIL checks. Check the signal clipping, it must occur at 482Vpp (see Fig.3 Trace A,B,C). SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK:

20、SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK: Set the LEVEL pot to minimum, set the scope timebase at 1V/div. 200S/ div., then increase the level and check the SIGNAL/CLIP led activity: it must turn on (green light) when the amplifier output is higher than 1Vp. Set the scope at 20V/div. and inc

21、rease the level, check the led: it must Fig. 1Fig. 1Fig. 1Fig. 1Fig. 1 Trace A (20V/div.) Trace B (5V/div.) RadioFans.CN 收音机爱 好者资料库 3 3 3 3 3 J J J J J change from green to red colour at the amplifier output signal clipping. CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHE

22、CK:CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHECK: Set both the scope channels sensitivity to 0.5V/div., connect the scope CH1 GND clip at CN3 pin 2 (AMP output) and the probe tip at TR6 (NPN) emitter, connect the CH2 probe tip at

23、 TR13 (PNP) emitter. Set the generator to have approx. 1Vp on the emitters: their difference must be less than 0.2V on the peaks (see Fig.4 Trace A & B). Connect a 4 500W load. Increase the input signal, the output current limiter must keep the emitter voltages, both half channel, at 1.5Vp approx. (

24、see Fig.5 Trace A). Temporarily short the amplifier output: the current limiter must keep the emitter voltages (both half channel) at 1 approx. (see Fig.5 Trace B). OFFSET SENSOR CHECK:OFFSET SENSOR CHECK:OFFSET SENSOR CHECK:OFFSET SENSOR CHECK:OFFSET SENSOR CHECK: Set the Variac to zero voltage out

25、put, disconnect the amplifier load and the supply connection to the Power board (CN1,2,4), turn on the ampli- fier, connect temporarily (by means of a suitable conductor wire) CN2 pin 2 to +15Vdc (CN3 pin 5), the PROTECT led must turn on in 5 seconds approx. Remove the connection, wait until the led

26、s turn off and after some sec- onds repeat the check with -15Vdc (available on CN3 pin 3), the led PROTECT must turn on again. BIAS CHECK:BIAS CHECK:BIAS CHECK:BIAS CHECK:BIAS CHECK: Disconnect CH2 probe. Connect the CH1 scope GND clip to CN2 pin 1 (GND terminal) and its probe tip to CN2 pin 2 (AMP

27、output). Adjust the generator level until the sinewave appears at full screen amplitude, no crossover distortion must be detectable: if necessary re-adjust R32. BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK: Set CH1 scope sensitivity at 20V/div., increase the genera

28、tor level to have 80Vpp, sweep the generator frequency from 20Hz to 20KHz: the output level must have not detectable level changes. SLEW RATE CHECK:SLEW RATE CHECK:SLEW RATE CHECK:SLEW RATE CHECK:SLEW RATE CHECK: Set the scope sensitivity to 10V/div. 1S/div. and set the generator to 1KHz square wave

29、 mode. Check the output square wave rising and falling edge slopes: both must be 10V/S or more as shown in Fig 6. Inputs & Protections Board CheckInputs & Protections Board CheckInputs & Protections Board CheckInputs & Protections Board CheckInputs & Protections Board Check These procedures are inte

30、nded for one channel at a time, repeat these operations for the other channel. SETUP:SETUP:SETUP:SETUP:SETUP: Connect the CH1 probe to amplifier input of the channel under test and set both at 500mV/div. 200mS/div. Connect the CH2 probe to amplifier output of the channel under test and set it at 10m

31、V/div. 200mS/div. Set the audio generator at 1KHz sinus. 775mVRMS (0dB). Set the LEVEL potentiometers full clockwise. The load resistor is disconnected. CMRR ADJUSTMENTCMRR ADJUSTMENTCMRR ADJUSTMENTCMRR ADJUSTMENTCMRR ADJUSTMENT Temporarily disconnect pin 3 from pin 1 and short the pin 2 (positive i

32、nput) and pin 3 (negative input) of XLR input socket. Adjust the trimmer R6 (channel A) or R19 (channel B) to obtain the minimum output level. GAIN ADJUSTMENTGAIN ADJUSTMENTGAIN ADJUSTMENTGAIN ADJUSTMENTGAIN ADJUSTMENT Re-set the input signal at pin 2 (positive input) and pin 3 (negative input) shor

33、t with pin 1 (GND) of XLR input socket. Set CH2 scope at 500mV/div. and connect it to the output of INPUTS & PROTECTIONS board (CN4 pin 10 for channel A or CN4 pin 12 for channel B). Set the input SENSITIVITY (SW1) at 1.75Vrms, adjust the trimmer R9 (channel. A) or R17 (channel B) to obtain the same

34、 amplitude of the scope signals. Fig. 2Fig. 2Fig. 2Fig. 2Fig. 2 Fig. 3Fig. 3Fig. 3Fig. 3Fig. 3 Fig. 5Fig. 5Fig. 5Fig. 5Fig. 5 Trace A (0.5V/div.) Trace B (0.5V/div.) Fig. 4Fig. 4Fig. 4Fig. 4Fig. 4 Trace A (0.5V/div.) Trace B (0.5V/div.) AMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKAMP

35、LIFIER GAIN CHECKAMPLIFIER GAIN CHECK Set CH2 scope at 20V/div. and connect it to the amplifier output of the channel under test. By means of the SENSITIVITY switch check the output levels: at 775mV position the output voltage must be 501.5Vp and at 1.75V position must be 22.50.5Vp. SIGNAL TO NOISE

36、RATIO CHECKSIGNAL TO NOISE RATIO CHECKSIGNAL TO NOISE RATIO CHECKSIGNAL TO NOISE RATIO CHECKSIGNAL TO NOISE RATIO CHECK Disconnect the audio generator and short the input (pin 1,2,3 of XLR socket shorted) the output signal (noise) must be less 1mV. AdvicesAdvicesAdvicesAdvicesAdvices Check the chann

37、els one at time to determine which is right (note: if you have a spare amplifier module that you know as right, use it). If you have determinate that the problem is a short on a rail, you must check the output transistors. To determine which transistor devices are bad, use a soldering iron to lift o

38、ne leg of each emitter pin and measure the emitter-collector resistance on each device. Unsolder and lift one leg of each base pin and check the base-collector resistance of each transistor and replace any that measure as a short. If all the transistors are OK, unsolder and lift one leg of each diod

39、e and check them. Check the circuit board for open foil traces. Use the Multimeter as Ohm-meter to check the resistors, particularly the base and emitter resistors of damaged transistor. If the input sinewave appears to be distorted during the negative cycle, you can assume that the problem is locat

40、ed somewhere in the circuitry of the positive low rail. If the positive cycle appears distorted, you can assume that the problem is in the circuitry of the negative low rail. If the high rails appear distorted or are not modulating as shown in figure, then the problem probably exists somewhere in th

41、e circuitry of the re- spective (+ or -) defective high rail. Refer to the schematics. Fig. 6Fig. 6Fig. 6Fig. 6Fig. 6 Trace A (10V/div.) Trace B (20V/div.) Trace A (20V/div.) Trace C (20V/div.) Trace B (20V/div.) Trace A (20V/div.) Trace C (20V/div.) RadioFans.CN 收音机爱 好者资料库 J J J J J 4 4 4 4 4 5 5 5

42、 5 5 J J J J J J J J J J 6 6 6 6 6 7 7 7 7 7 J J J J J Spare Part ListSpare Part ListSpare Part ListSpare Part ListSpare Part List CodeRef.Description AccessoriesAccessoriesAccessoriesAccessoriesAccessories 277317Owners Manual P-Series AssemblyAssemblyAssemblyAssemblyAssembly 667641MSSCEM01Cover 667

43、640FIN27121Chassis 667639MSSEB901Front Panel 657232Level Knob 347200Cord Lock 238082238082238082238082238082FIN27141FIN27141FIN27141FIN27141FIN27141Transformer 300W 230VacTransformer 300W 230VacTransformer 300W 230VacTransformer 300W 230VacTransformer 300W 230Vac 130294Mains Cord (EU) 110285Power Sw

44、itch 778123FIN27161Cables Assembly HeadPhones & Display AssembliesHeadPhones & Display AssembliesHeadPhones & Display AssembliesHeadPhones & Display AssembliesHeadPhones & Display Assemblies 768137768137768137768137768137FIN27104FIN27104FIN27104FIN27104FIN27104HeadPhones Board (Pcb# 9610045)HeadPhon

45、es Board (Pcb# 9610045)HeadPhones Board (Pcb# 9610045)HeadPhones Board (Pcb# 9610045)HeadPhones Board (Pcb# 9610045) 140207Horizontal Female Jack Socket 768138768138768138768138768138FIN27106FIN27106FIN27106FIN27106FIN27106Led On/Off Board (Pcb# 9405022)Led On/Off Board (Pcb# 9405022)Led On/Off Boar

46、d (Pcb# 9405022)Led On/Off Board (Pcb# 9405022)Led On/Off Board (Pcb# 9405022) 768133768133768133768133768133FIN27103FIN27103FIN27103FIN27103FIN27103Display Board (Pcb# 9610044)Display Board (Pcb# 9610044)Display Board (Pcb# 9610044)Display Board (Pcb# 9610044)Display Board (Pcb# 9610044) 080742*Led

47、 3mm Wide Diffused Red-Grn 080710*Led 3mm 60deg Diffused Yel 080705*Led 3mm 60deg Diffused Red 074561RESVRD01*4K7 Linear Rotary Potentiometer Inputs & Protections AssemblyInputs & Protections AssemblyInputs & Protections AssemblyInputs & Protections AssemblyInputs & Protections Assembly 768135768135

48、768135768135768135FIN27101FIN27101FIN27101FIN27101FIN27101Inputs & Protections Board (Pcb# 9610033)Inputs & Protections Board (Pcb# 9610033)Inputs & Protections Board (Pcb# 9610033)Inputs & Protections Board (Pcb# 9610033)Inputs & Protections Board (Pcb# 9610033) 230557*1uh Hor Coil For Amplifier 14

49、0228*Horizontal Jack Stereo Socket 140226*Horizontal Jack Mono Socket 110307*Relay 24V / 2 Switch 5A 250V 110295*4sw 2pos Vertical Slider Switch 110293*2sw 2pos Slider Switch 100061*TL072 Dual J-Fet Operational Amplifier 090194*BC560 TO92 LN Pnp Transistor 090183*BC550 TO92 LN Npn Transistor 080245*7V5 1W 5% Zener Diode 080156*1N4002 1A 100V Rectifier Diode 080103*1N4148 100mA 75V Signal Diode 070241*100K 20% Horizontal Linear Trimmer 070121*1K 20% Horizontal Linear Trimmer 060540*3K3 1W 5% Resistor 060481*820E 5W 10% Resistor 06