LEM-AMP2_4-pwr-sm 维修电路原理图.pdf

1 1 1 1 1 J J J J JIndexSoldering point.Male connector.Female connector.M/F faston connector.Test point.Supply voltage.Logic supply ground.Analog supply ground.Chassis ground.Earth ground.Flag joined with one or more flagsGENERALMUSIC S.p.A. Sales Division: 47842 S.Giovanni in Marignano (RN) ITALY - Via delle Rose, 12 - tel. 0541/959511 - fax 0541/957404GENERALMUSIC on the NET: http:/Technical Specifications, Introduction, Test Procedures & Adjustments2Schematic Diagrams4Layout & Spare Part List5SERVICE MANUALL CODE: 270232MWarningswith the same signal name inscribed.AddressATTENTIONObserve precautions when handling electrostatic sensitive devices.NoticeService must be carried out by qualified personnel only.Any tampering carried out by unqualified personnel during the guarantee periodwill forfeit the right to guarantee.For a correct operation of the instrument, after having switched off, be careful to wait at least 3 seconds before switching on again.To improve the devices specifications, the schematic diagrams may be subject to change without prior notice.All components marked by this symbol have special safety characteristics, when replacing any of these components use onlymanufacturers specified parts.The () micro symbol of capacitance value is substituted by U.The () omega symbol of resistance value is substituted by E. The electrolytic capacitors are 25Vdc rated voltage unless otherwise specified.All resistors are 1/8 unless otherwise specified.All switches shown in the OFF position. All DC voltages measured to ground with a voltmeter 20KOhm/V.RadioFans.CN 收音机爱 好者资料库J J J J J 2 2 2 2 2TECHNICAL SPECIFICATIONSTECHNICAL SPECIFICATIONSTECHNICAL SPECIFICATIONSTECHNICAL SPECIFICATIONSTECHNICAL SPECIFICATIONSDimensions:(WxHxD)483x44x310mm (1U)Weight:8KgPower Requirements:(230Vac10% 50Hz)300VAOutput Power:(8 stereo/parallel)2x 130WattsMax. Undistorted Out: (8 stereo/parallel)92VppInput Sensitivity:(constant sensitivity)0.775Vrms (0dB)Input Impedance:(balanced)30K(unbalanced)15KVoltage Gain:(constant sensitivity)320.5dBSlew Rate:10V/SDamping Factor:(8 stereo/parallel)400Frequency Response(-0.2dB)20Hz20KHzat Full Power:(-3dB)10Hz60KHzIMD:(SMPTE 60Hz/7KHz 4:1)0.1%THD:(THD+N)95dBCrosstalk:(1KHz)70dBTEST PROCEDURES & ADJUSTMENTSTEST PROCEDURES & ADJUSTMENTSTEST PROCEDURES & ADJUSTMENTSTEST PROCEDURES & ADJUSTMENTSTEST PROCEDURES & ADJUSTMENTSPrecautionPrecautionPrecautionPrecautionPrecaution To prevent short circuit during any test, the oscilloscope must bethe oscilloscope must bethe oscilloscope must bethe oscilloscope must bethe oscilloscope must beEARTH insulatedEARTH insulatedEARTH insulatedEARTH insulatedEARTH insulated, this occurs because some test require to connect itsprobe to the amplifier output, non-compliance may cause damages tooscilloscope inputs circuitry. Before removing or installing any modules and connectors, disconnectdisconnectdisconnectdisconnectdisconnectthe amplifier from AC MAINSthe amplifier from AC MAINSthe amplifier from AC MAINSthe amplifier from AC MAINSthe amplifier from AC MAINS and measure the DC supply voltagesacross each of the power suppliy capacitors. If your measurement on anyof the caps is greater than 10Vdc, connect a 100 10W resistor acrossthe applicable caps to discharge them for your safety. Remember toremove the discharge resistor immediately after discharging caps. Do notDo notDo notDo notDo notpower up the amplifier with the discharge resistor connectedpower up the amplifier with the discharge resistor connectedpower up the amplifier with the discharge resistor connectedpower up the amplifier with the discharge resistor connectedpower up the amplifier with the discharge resistor connected. Read these notes entirely before proceeding to any operation. Thesenotes are not comprehensive of all damages that possibly occur, butincludes some specifically advices, checks and adjustments relative tothis amplifier.RemarksRemarksRemarksRemarksRemarks The power supply utilizes a dual bipolar DC rail configuration with low andhigh voltages; one positive and one negative low rail (+/-Vcc1) and onepositive and one negative high rail (+/-Vcc2). Some component references in the circuitry have the A letter suffix toidentify the CH1 channel and the B letter for CH2 channel.Visual CheckVisual CheckVisual CheckVisual CheckVisual Check Use compressed air to clear dust in the amplifier chassis. Before proceed to supply the amplifier check visually the internal assem-bly, if appears an evident damage find the most possible reasons thatcause 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 InstrumentsTest 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 zerovoltage. Set the amplifier in STEREO MODE and turn full clockwise the LEVELpotentiometers. Connect the audio generator to the channel inputs and set it to 1KHz775mVRMS (0dB) sinusoidal signal. The procedures that follow must be executed subsequently in the orderspecified.Supply CheckSupply CheckSupply CheckSupply CheckSupply Check Remove the transformer secondary fuses (located on SUPPLY & PRO-TECTIONS board), set the Variac to the nominal mains voltage, checkwith the Multimeter the AC supply voltages:FUSE1-FUSE2=551.5VacFUSE3-FUSE4=903Vac. Re-set the Variac at zero voltage, turn off the amplifier and put the fusesback on its holders. Connect the oscilloscope probes ch1/2 to the channel outputs, beforeRL1, set both to 20V/div. 200S/div. Set up the Variac slowly monitoring the Outputs with the oscilloscopech1/2 connected, it should display the sinusoidal input signal amplifiedwith no distortions, if a distortion occur check the POWER AMPLIFIERboards as suggested in the ADVICES section. If the protection trips, turn off the amplifier, wait some minutes anddisconnect the supplies from the outputs modules (CN1, CN4 on POWERAMPLIFIER boards), continue to check 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,CAUTION: Before re-connecting the output modules to the supplies,you 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 ayou must have the capacitors discharged for your safety: connect a100100100100100 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 across the caps and remove the resistor just afterthey are discharged.they are discharged.they are discharged.they are discharged.they are discharged. Finally verify the DC supplies on POWER SUPPLIES board:CN2-4 pin 3 (+Vcc2)=+612VdcCN2-4 pin 4 (+Vcc1)=+361.5VdcCN2-4 pin 2 (-Vcc1)=-361.5VdcCN2-4 pin 1 (-Vcc2)=-612VdcCN3 pin 5=+151VdcCN3 pin 3=-151Vdc If one or more voltages dont correspond, check the rectifiers, capacitorsand transformers disconnecting them from circuitry, refer to schematics.Channels CheckChannels CheckChannels CheckChannels CheckChannels Check The CH1 channel is on the left and CH2 channel is on the right of thechassis. These procedures are intended for one channel at a time, repeat theseoperation for the other channel. Verify, with the Multimeter, the insulation between the heatsink and thetransistors collectors. Verify, with the Multimeter, the PTC resistor value (R133 connectedacross 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 CN102 pin 1 (GND terminal).Connect the ch1 probe tip to CN102 pin 2 (AMP output).Connect the ch2 probe tip to D109 anode and set it sensitivity at 5V/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 inFig.1 Trace A (Trace B shown the amplifier 2nd stage input). If there is adistortion read the section ADVICES and proceed to check the otherchannel. BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT:Set the generator level at zero, connect the Multimeter across the emitterand collector of TR108, then adjust R132 trimmer to read 2.5Vdc. HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:Connect the ch2 probe tip to D103 cathode and set it sensitivity at 20V/div.When the output signal (Positive half-wave) is less than 30Vp the voltageon D103 cathode must remain constant at 36V, when the output signalexceeds 30Vp the voltage must follow the output signal with 6V offset(see Fig.2 Trace B), to check the negative high rail connect the probe toD114 anode (see Fig.2 Trace C).Connect the 8 300W load on the output and repeat the INITIAL andHIGH RAIL checks.Check the signal clipping, it must occur at 482Vpp (see Fig.3 TraceA,B,C). 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 scope timebase at 1V/div. 200S/div., then increase the level and check the SIGNAL/CLIP led activity: itmust turn on (green light) when the amplifier output is higher than 1Vp.Set the scope at 20V/div. and increase the level, check the LIMITER ledFig. 1Fig. 1Fig. 1Fig. 1Fig. 1Trace 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 Jactivity: it must turn on (red light) at the amplifier output signal clipping. 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 both the scope channels sensitivity to 0.5V/div., connect the scopech1 GND clip at CN3 pin 2 (AMP output) and the probe tip at TR106(NPN) emitter, connect the ch2 probe tip at TR113 (PNP) emitter.Set the generator to have approx. 1Vp on the emitters: their differencemust 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 currentlimiter must keep the emitter voltages, both half channel, at 1.5Vpapprox. (see Fig.5 Trace A).Temporarily short the amplifier output: the current limiter must keep theemitter 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 output, disconnect the amplifier load andthe supply connection from the Power Supply & I/O Board (CN2-4), turnon the amplifier, connect temporarily (by means of a suitable conductorwire) CN2 pin 2 to +15Vdc (CN3 pin 5), the PROTECT led must turn on in5 seconds approx.Remove the connection, wait until the leds turn off and after some sec-onds repeat the check with -15Vdc (available on CN3 pin 3), the ledPROTECT 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 output). Adjust thegenerator level until the sinewave appears at full screen amplitude, nocrossover distortion must be detectable: if necessary re-adjust R132. BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK:Set ch1 scope sensitivity at 20V/div., increase the generator level to have80Vpp, sweep the generator frequency from 20Hz to 20KHz: the outputlevel 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 to1KHz square wave mode. Check the output square wave rising and fallingedge 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 intended for one channel at a time, repeat theseoperations for the other channel. SETUP:SETUP:SETUP:SETUP:SETUP:Connect the ch1 probe to amplifier input of the channel under test and setit at 500mV/div. 200mS/div.Connect the ch2 probe to amplifier output of the channel under test andset it at 10mV/div. 200mS/div.Set the audio generator at 1KHz sinus. 775mVRMS (0dB).Set the LEVEL potentiometers full clockwise.The load resistor is disconnected. AMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKAMPLIFIER GAIN CHECKCheck the output levels: at 775mV position the output voltage must be461.5Vp. SIGNAL TO NOISE RATIO CHECKSIGNAL TO NOISE RATIO CHECKSIGNAL TO NOISE RATIO CHECKSIGNAL TO NOISE RATIO CHECKSIGNAL TO NOISE RATIO CHECKDisconnect the audio generator the output signal (noise) must be less1mV.AdvicesAdvicesAdvicesAdvicesAdvices Check the channels one at time to determine which is right (note: if youhave 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 mustcheck the output transistors.To determine which transistor devices are bad, use a soldering iron to liftFig. 2Fig. 2Fig. 2Fig. 2Fig. 2Fig. 3Fig. 3Fig. 3Fig. 3Fig. 3Fig. 5Fig. 5Fig. 5Fig. 5Fig. 5Trace A (0.5V/div.)Trace B (0.5V/div.)Fig. 4Fig. 4Fig. 4Fig. 4Fig. 4Trace A (0.5V/div.)Trace B (0.5V/div.)one leg of each emitter pin and measure the emitter-collector resistanceon each device. Unsolder and lift one leg of each base pin and check thebase-collector resistance of each transistor and replace any that measureas a short.If all the transistors are OK, unsolder and lift one leg of each diode andcheck them.Check the circuit board for open foil traces.Use the Multimeter as Ohm-meter to check the resistors, particularly thebase 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 located somewhere in the circuitry ofthe positive low rail.If the positive cycle appears distorted, you can assume that the problemis 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 re-spective (+ or -) defective high rail. Refer to the schematics.Fig. 6F