General_Music_LEM_P1000_Service_Manual电路图.pdf

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1、1 1 1 1 1 J J J J J CODE : 277320 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, re- place with a new one. Test InstrumentTest Ins

3、trumentTest InstrumentTest InstrumentTest Instrument Audio Generator Dual Trace Oscilloscope Digital Multimeter 2 2000W, 4 1000W, 8 1000W, 100 100W resistors Variac Temperature Meter SetupSetupSetupSetupSetup Connect the Variac between the PROTECTION board and the TF1 and TF2 transformers and set it

4、 at zero voltage. Set the amplifier in STEREO 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. Insert the temperature meter through the IC1 interstice located at centre of heatsink. The proce

5、dures that follow must be executed subsequently in the order specified. Supply CheckSupply CheckSupply CheckSupply CheckSupply Check Remove the transformer secondary fuses (located on FUSE board), set the Variac to the nominal mains voltage, check with the Multimeter the phase opposition between the

6、 secondaries of the two transformers (F1- F2,F3-F4), if not, verify the primary connections (T1T4 on Protections Board). Verify the AC supply voltages:F1-F2=722VacF3-F4=1283Vac. Re-set the Variac at zero voltage, turn off the amplifier and put the fuses back on its holders. Connect the oscilloscope

7、probes CH1/2 to the channel outputs, 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 check the Driver and the Power Boards as sugge

8、sted in the ADVICES section. If the protection trips, turn off the amplifier, wait some minutes and dis- connect the supplies from the outputs modules (CN1 - CN2 - CN7 - CN8 on POWER boards), continue to check the supplies. CAUTION: Before re-connecting the output modules to the supplies,CAUTION: Be

9、fore 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 capacitors discharged for your s

10、afety: 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 safety: connect a 100100100100100 100

11、W resistor across the caps and remove the resistor just 100W resistor across the caps and remove the resistor just 100W resistor across the caps and remove the resistor just 100W resistor across the caps and remove the resistor just 100W resistor across the caps and remove the resistor just after th

12、ey are discharged.after they are discharged.after they are discharged.after they are discharged.after they are discharged. Finally verify the DC supplies on Supply Board: CN6 (+Vcc2)=+89.52Vdc CN8 (+Vcc1)=+501.5Vdc CN7 (-Vcc1)=-501.5Vdc CN2 (-Vcc2)=-89.52Vdc on Protections Board: CN2 pin3=+271Vdc CN

13、3 pin3=-271Vdc CN1 pin4-5-6=+13.81Vdc CN1 pin1-2-3=-13.81Vdc 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 is faci

14、ng the front and channel B the rear 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. SETUP:SETUP:SETUP:SETUP:SETUP: Connect the CH1 s

15、cope GND clip to CN5 (GND terminal). Connect the CH1 probe tip to CN6 (AMP output). Connect the CH2 probe tip to D2 cathode on POWER board. Set the LEVEL potentiometers full clockwise. The load resistor is disconnected. INITIAL TEST:INITIAL TEST:INITIAL TEST:INITIAL TEST:INITIAL TEST: Increase slowl

16、y the Variac. The channel output signals must be symmetri- cal respect the GND without visible distortion and oscillation as shown in Fig.1 Trace A. If there is a distortion read the section ADVICES and proceed to check the other channel. Verify that, when the heatsink temperature is less 50c, the c

17、ooling fan Fig. 1Fig. 1Fig. 1Fig. 1Fig. 1 Trace B (20V/div.) Trace A (20V/div.) Trace C (20V/div.) RadioFans.CN 收音机爱 好者资料库 3 3 3 3 3 J J J J J voltage must be between 12 and 16V. HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK: When the output signal (Positive half-wa

18、ve) is less than 44Vp the voltage on D2 cathode must remain constant at 50V, when the output signal exceeds 44Vp the voltage must follow the output signal with 6V offset (see Fig.1 Trace B), to check the negative high rail connect the probe to D18 anode (see Fig.1 Trace C). Connect the 4 1000W load

19、on the output and repeat the INITIAL and HIGH RAIL checks. Check the signal clipping, it must occur at 1305Vpp (see Fig.2 Trace ABC). SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK: Set the LEVEL pot to minimum, set the sc

20、ope 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 5Vpp. Set the scope at 50V/div. and increase the level, check the led: it must change from green to red colour when the amplifier

21、 output signal clip. CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHECK: Set the CH2 sensitivity to 0.5V/div., connect the scope CH1, GND clip at CN6 (AMP o

22、utput) and the probe tip at CN5 (GND terminal), CH2 probe tip alternatively on TR6, TR11 (NPN) and TR16, TR22 (PNP) emitters. Set the generator to have approx. 1Vp on the emitters: their difference must be less than 10% one each other (see Fig.3 Trace A). The NPN or PNP transistors out of tolerance

23、must be replaced with a new selected pair. Connect a 2 2000W load. Connect the CH1 probe tip on TR16 emitter and the CH2 probe tip on TR11 emitter. Increase the input signal, the output current limiter must keep the emitter voltages (both half channel) at 1.2Vp approx. (see Fig.3 Trace B). Temporari

24、ly short the amplifier output: the current limiter must keep the emitter voltages (both half channel) at 0.7Vp (see Fig.3 Trace C). COOLING FAN the fan must run at maximum speed). Reset the protection turning off the amplifier, turn it on again, connect temporarily (by means of a suitable conductor

25、wire) CN6 to -15Vdc, the led PROTECT must turn on again. SOA ADJUSTMENT:SOA ADJUSTMENT:SOA ADJUSTMENT:SOA ADJUSTMENT:SOA ADJUSTMENT: Set the scope sensitivity at 5V/div. (both channels) and connect the CH1 probe on D12 cathode and the CH2 probe on D11 anode on Driver board, check the voltage across

26、D12 and D11 zener diodes: it must be 14.80.1V; increasing 10dB the generator level this voltage does not decrease more than 0.5V. Connect the 4 1000W load, set the scope sensitivity at 2V/div. and connect the CH1 probe tip at R43 side CN3 and the CH2 probe tip at R36 side CN2. Decrease the signal le

27、vel until two sinusoid appear on the scope as shown in Fig 4 Trace AB. Their max. amplitude must be 5.5Vp (the outer) and 1.5Vp (the inner) as shown in Fig 5 Trace A,B; increasing a bit the generator signal, the inner sinusoid must produce spikes on its peaks as shown in Fig 5 Trace A,B. Connect the

28、 2 1000W load, set the scope sensitivity at 1V/div. (both channels) and connect its probes to the collectors of TR8 (CH1) and TR11 (CH2) on Driver Board. Disconnect the fan; wait until the temperature is 90C (require some minutes) then decrease the input to zero. Adjust the trimmers R20 and R40, unt

29、il the scope traces go respectively at -2.2Vdc and +2.3Vdc; turn on the cooling fan and wait until the tem- perature goes down to 80C; then turn it off. Fig. 2Fig. 2Fig. 2Fig. 2Fig. 2 Fig. 3Fig. 3Fig. 3Fig. 3Fig. 3 Trace A (0.5V/div.) Trace B (0.5V/div.) Trace C (0.5V/div.) Fig. 5Fig. 5Fig. 5Fig. 5F

30、ig. 5 Trace A (2V/div.) Trace C (20V/div.) (Amplifier Output) Trace B (2V/div.) Fig. 4Fig. 4Fig. 4Fig. 4Fig. 4 Trace A (2V/div.) Trace C (20V/div.) (Amplifier Output) Trace B (2V/div.) Reconnect the 4 1000W load, adjust the level for the maximum dis- placement of the scope tracks toward the centre o

31、f the scope screen (- 3dB approx.); the SOA control circuit (Protect led light on) will start at 902C. Reconnect the cooling fan and check with the Multimeter its supply volt- age: it must be 20V or more (max speed). At 70C heatsink temperature, short circuit the amplifier output and check the scope

32、 traces: they must displace 1V toward the centre of the screen, respect to the previous position with 4 load. Remove the short and decrease the input level to zero. The temperature will decrease: at 65.75C the speed of the cooling fan must change from max to min speed. In case of a fan misbehaviour

33、try to replace the D10 zener diode: if speed change at 75C or more replace with a lower volt- age zener diode, if speed change at 60C or less replace with a higher voltage zener diode. BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT: Connect the Multimeter across R54

34、of Power board, when the heatsink temperature rises at 50C, turn off the cooling fan and adjust R31 to read 2mV. Set the scope sensitivity at 1V/div.(CH1), and connect the GND clip to the amplifier GND (CN5) and the probe tip on the output (CN6). Adjust the generator level until the sinewave appears

35、 at full screen amplitude, No crossover distortion must be detectable: if necessary re-adjust R31. Re- connect the fan. BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK: Sweep the generator frequency from 20Hz to 20KHz, the output level must have not detectable level c

36、hanges. SLEW RATE CHECK:SLEW RATE CHECK:SLEW RATE CHECK:SLEW RATE CHECK:SLEW RATE CHECK: Set the scope sensitivity to 10V/div. 1mS/div. and set the generator to 1KHz square wave mode. Check the output square wave rising and falling edge slopes: both must be 12V/S or more. Disconnect the Variac and r

37、e-connect the transformer primaries to the PROTECTIONS board (be careful to connect the two transformers out of phase). Inputs Board CheckInputs Board CheckInputs Board CheckInputs Board CheckInputs Board Check These procedures are intended for one channel at a time, repeat these operations for the

38、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 10mV/div. 200mS/div. Set the audio generator at 1KHz sinus. 775mVRM

39、S (0dB). Set the LEVEL potentiometers full clockwise. The load resistor is disconnected. CMRR ADJUSTMENTCMRR ADJUSTMENTCMRR ADJUSTMENTCMRR ADJUSTMENTCMRR ADJUSTMENT Temporarily disconnect pin 3 from pin 1and short the pin 2 (positive input) and pin 3 (negative input) of XLR input socket. Adjust the

40、trimmer R10 (channel A) or R21 (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) short with pin 1 (GND) of XLR input socket Set CH2 scope at 500mV/di

41、v. and connect it to the output of INPUTS board (CN3 pin9 for channel A or CN3 pin7 for channel B). Set the input SENSITIVITY (SW1) at 2.25Vrms, adjust the trimmer R5 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 (channel. A) or R17 (channel B)

42、to obtain the same amplitude of the scope signals. AMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECK Set CH2 scope at 50V/div. and connect it to the amplifier output of the channel under test. By means of the SENSITIVITY switch check the output leve

43、ls: at 775mV position the output voltage must be 631.5Vp and at 2.25V position must be 22.50.5Vp. AMPLIFIER BRIDGE MODE CHECKAMPLIFIER BRIDGE MODE CHECKAMPLIFIER BRIDGE MODE CHECKAMPLIFIER BRIDGE MODE CHECKAMPLIFIER BRIDGE MODE CHECK Set the amplifier in BRIDGE mode (input signal to channel A), conn

44、ect the CH2 probe to the bridge output: the output voltage must be 1243Vp. SIGNAL TO NOISE 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

45、output signal (noise) must be less 1mV. AdvicesAdvicesAdvicesAdvicesAdvices Check the channels one at time to determine which is right (note: if you have a spare amplifier module that you know as right, use it). If the other channel doesnt work properly, you can replace the DRIVER and POWER board on

46、e a time, using those of the right channel, to isolate where is the damage. If you have determinate that the problem is a short on a rail, you must check the output transistors. To do this you must remove before the DRIVER board to access at the POWER board. To determine which transistor devices are

47、 bad, use a soldering iron to lift one 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, un

48、solder and lift one leg of each diode 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

49、can assume that the problem is located 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 the circuitry of the respec- tive (+ or -) defective high rail. Refer to the schematics. 1KHz THD+N vs Input Level SMPTE (%) vs Input Level Common Mode Rejection Ratio Frequency & Phase Response THD+N (%) vs