LEM-P500-pwr-sm 维修电路原理图.pdf

《LEM-P500-pwr-sm 维修电路原理图.pdf》由会员分享，可在线阅读，更多相关《LEM-P500-pwr-sm 维修电路原理图.pdf（8页珍藏版）》请在收音机爱好者资料库上搜索。

1、1 1 1 1 1 J J J J JCODE : 277319Index & WarningsSoldering point.Male connector.Female connector.M/F faston connector.Test point.Supply voltage.Logic supply ground.Analog supply ground.Signal ground.Chassis ground.Flag joined with one or more flags with the same signal name inscribed.GENERALMUSIC S.p

2、.A. Sales Division: 47842 S.Giovanni in Marignano (RN) ITALY - Via delle Rose, 12 - tel. 0541/959511 - tlx 550555 GMUSIC I - fax 0541/957404Technical Specifications, Test Procedures & Adjustments2NoticeService must be carried out by qualified personnel only. Any tampering carried out by unqualified

3、personnel during the guarantee period will 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 witho

4、ut prior notice.Schematic NotesAll components marked by this symbol have special safety characteristics, when replacing any of these components use only manufacturers specified parts.The () micro symbol of capacitance value is substituted by U. The () omega symbol of resistance value is substituted

5、by E. The electrolytic capacitors are 25Vdc rated voltage unless otherwise specified. All resistors are 1/4W unless otherwise specified.ATTENTIONObserve precautions when handlingelectrostatic sensitive devicesSERVICE MANUALSchematic DiagramsLayout4Wiring Connections67Power Amplifier BoardInputs Boar

6、d, Supplies & Protections Board58Display Board & Part ListRadioFans.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)483x88x325mm (2U)Weight:13KgPower Requirements:(230Vac10% 50Hz

7、)500VAOutput Power:(4 stereo/parallel)2x 300Watts(8 stereo/parallel)2x 200Watts(8 bridge)600Watts(16 bridge)400WattsMax. Undistorted Out: (4 stereo/parallel)98Vpp(8 stereo/parallel)113Vpp(8 bridge)194VppInput Sensitivity:(constant sensitivity)0.775Vrms (0dB)(constant gain)1.75Vrms (+7dB)Input Impeda

8、nce:(balanced)30K(unbalanced)15KVoltage Gain:(constant sensitivity)330.5dB(constant gain)260.5dBSlew Rate:25V/SDamping Factor:(4 stereo/parallel)400(8 stereo/parallel)800Frequency Response(-0.2dB)20Hz20KHzat Full Power:(-3dB)10Hz60KHzIMD:(SMPTE 60Hz/7KHz 4:1)0.1%THD:(THD+N)95dBCrosstalk:(1KHz)60dBTE

9、ST 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

10、 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

11、 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 capacit

12、ors. If your measurement on anyof the caps is greater than 10Vdc, connect a 100 20W 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 dischar

13、ge 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 proc

14、eeding 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 vo

15、ltages; one positive and one negative low rail (+/-Vcc1) and onepositive 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 amplifier check visually the internal ass

16、em-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, re-place with a new one.Test InstrumentsTest InstrumentsTest InstrumentsTest Instrume

17、ntsTest Instruments Audio Generator Dual Trace Oscilloscope Digital Multimeter 2 1000W, 4 500W, 100 20W resistors Variac (0250Vac) Temperature MeterSetupSetupSetupSetupSetup Connect the Variac between the mains and the amplifier and set it at zerovoltage. Set the amplifier in STEREO MODE and turn fu

18、ll clockwise the LEVELpotentiometers. Connect the audio generator to the channel inputs and set it to 1KHz775mVRMS (0dB) sinusoidal signal. Insert the temperature meter through the IC3 interstice located at centreof heatsink. The procedures that follow must be executed subsequently in the orderspeci

19、fied.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:F1-F2=522VacF3-F4=903Vac. Re-set the Variac at zero voltage,

20、 turn off the amplifier and put the fusesback on its holders. Connect the oscilloscope probes CH1/2 to the channel outputs, beforeRL1 and RL2, 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 s

21、ignal 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 (CN2, CN3 on POWERAMPLIFIER boards), continue to check

22、 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-connec

23、ting 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: conne

24、ct ayou must have the capacitors discharged for your safety: connect a100100100100100 20W resistor across the caps and remove the resistor just after 20W resistor across the caps and remove the resistor just after 20W resistor across the caps and remove the resistor just after 20W resistor across th

25、e caps and remove the resistor just after 20W 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 SUPPLIES & PROTECTIONS Board:T8 (+Vcc2)=+612VdcT5 (+Vcc1)=+3

26、51.5VdcT6 (-Vcc1)=-351.5VdcT7 (-Vcc2)=-612VdcCN2 pin1=+231VdcCN3 pin3-4-5=+151VdcCN3 pin8-9-10 =-151Vdc If one or more voltages dont correspond, check the rectifiers, capacitorsand transformers disconnecting them from circuitry, refer to schematics.Channels CheckChannels CheckChannels CheckChannels

27、CheckChannels Check The channel A is facing the front and channel B the rear of the chassis. 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. SETUP:SET

28、UP:SETUP:SETUP:SETUP:Connect the CH1 scope GND clip to CN3 pin 1 (GND terminal).Connect the CH1 probe tip to CN3 pin 2 (AMP output).Connect the CH2 probe tip to D20 cathode.Set the LEVEL potentiometers full clockwise.The load resistor is disconnected. INITIAL TEST:INITIAL TEST:INITIAL TEST:INITIAL T

29、EST: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. If there is a distortion read the section ADVICES andproceed to check the other channel.Verify that, when the heatsink tem

30、perature is less than 50c, the coolingfan voltage must be between 10 and 14Vdc. HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:HIGH RAIL CHECK:When the output signal (Positive half-wave) is less than 30Vp the voltageon D20 cathode must remain constant at 36V, when the output signale

31、xceeds 30Vp the voltage must follow the output signal with 6V offset(see Fig.1 Trace B), to check the negative high rail connect the probe toD30 anode (see Fig.1 Trace C).Connect the 4 500W load on the output and repeat the INITIAL andHIGH RAIL checks.Check the signal clipping, it must occur at 482V

32、pp (see Fig.2 TraceA,B,C).Fig. 1Fig. 1Fig. 1Fig. 1Fig. 1Trace 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 JVerify the voltages across the diodes D19 and D26; they must be 14.80.5Vdc. SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHE

33、CK: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 incr

34、ease the level, check the led: it mustchange from green to red colour 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

35、CHECK:Set the CH2 sensitivity to 0.5V/div., connect the scope CH1, GND clip atCN3 pin 2 (AMP output) and the probe tip at TR26 (PNP) emitter, con-nect the CH2 probe tip at TR17 (NPN) emitter.Set the generator to have approx. 1Vp on the emitters: their differencemust be less than 0.2V on the peaks (s

36、ee Fig.3 Trace A & B).Connect a 2 1000W load. Increase the input signal, the output currentlimiter must keep the emitter voltages (both half channel) at 1.25Vpapprox. (see Fig.4 Trace A).Temporarily short the amplifier output: the current limiter must keep theemitter voltages (both half channel) at

37、0.80.1Vp (see Fig.4 Trace B). COOLING FAN & PROTECTION CHECK:COOLING FAN & PROTECTION CHECK:COOLING FAN & PROTECTION CHECK:COOLING FAN & PROTECTION CHECK:COOLING FAN & PROTECTION CHECK:Short circuit pins 15 and 16 of OC1, the fan must run at max. speed(2023Vdc on its tips).Short circuit pins 13 and

38、14 of OC1, the PROTECT led must turn onimmediately, the fan must run at max. speed. The PROTECT led of theother channel must also turn on after 2 Sec. and the relays must discon-nect the output sockets.Remove the short circuit, after 3 Sec. both PROTECT leds must turn offand the relays must re-conne

39、ct the output sockets.Temporarily short the emitter and the collector of TR1 the PROTECT ledmust turn on and the relays must disconnect the output sockets.Turn off the amplifier and wait a minute to let the supply caps discharge. OFFSET SENSOR CHECK:OFFSET SENSOR CHECK:OFFSET SENSOR CHECK:OFFSET SEN

40、SOR CHECK:OFFSET SENSOR CHECK:Set the Variac to zero voltage output, disconnect the amplifier load andthe supply connection to the Power board (CN2,3,4), turn on the ampli-fier, connect temporarily (by means of a suitable conductor wire) CN3 pin2 to +15Vdc (CN1 pin 5), the PROTECT led must turn on i

41、n 5 secondsapprox.; the fan must run at maximum speed).Remove the connection, wait until the leds turn off and after some sec-onds repeat the check with -15Vdc (available on CN1 pin 4), the ledPROTECT must turn on again. SOA ADJUSTMENT:SOA ADJUSTMENT:SOA ADJUSTMENT:SOA ADJUSTMENT:SOA ADJUSTMENT:Set

42、the scope sensitivity at 5V/div. (both channels).Disconnect the fan and cut the pins A-B of J16.Connect the 4 500W load and connect the CH2 probe tip at TR23collector, check the waveform as shown in Fig 5 Trace B, Trace A showCH1 that is also connected at TR26 (PNP) emitter.Set the scope CH2 sensiti

43、vity at 2V/div. and connect the probe tip at thetestpoint TP3.Set the load at 2, wait until the temperature reaches 80C; then changethe load back to 4.Adjust the generator level to have the CH1 waveshape as shown in Fig 6Trace A.Turn the R47 trimmer to level the peaks of the CH2 waveshape as shownFi

44、g 6 Trace b.Solder the pins A-B of J16: the CH2 trace becomes continuous.Increase the generator level for the max. displacement of the CH2 tracetoward the centre of the screen Fig 7 Trace b.Wait until the temperature reaches 88C, then turn clockwise the R62trimmer to activate the SOA control (that i

45、s displayed by CH1 trace whenits peak voltage decrease Fig 7 Trace A), after some seconds, the chan-nel goes in PROTECT mode.Set the CH2 sensitivity at 5V/div. then, with its tip, check the voltage onD19 cathode: it must be 14V or more.Activate the fan and check its supply voltage: it must be 20V or

46、 more(max. speed).Fig. 2Fig. 2Fig. 2Fig. 2Fig. 2Fig. 3Fig. 3Fig. 3Fig. 3Fig. 3Trace A (0.5V/div.)Trace B (0.5V/div.)Fig. 5Fig. 5Fig. 5Fig. 5Fig. 5Trace A (5V/div.)Trace B (5V/div.)Fig. 4Fig. 4Fig. 4Fig. 4Fig. 4Trace A (0.5V/div.)Trace B (0.5V/div.) BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIAS ADJUSTMENT:BIA

47、S ADJUSTMENT:BIAS ADJUSTMENT:Remove the CH2 probe, connect CH1 GND clip to CN3 pin 1 (GNDterminal) and its probe tip to CN3 pin 2 (AMP output) and set its sensitiv-ity at 1V/div.Set the generator level at zero, connect the Multimeter across the emit-ters of TR17 and TR26, when the heatsink temperatu

48、re reaches 55C,turn off the cooling fan and adjust R55 trimmer to read 60.5mV.Adjust the generator level until the sinewave appears at full screen ampli-tude, No crossover distortion must be detectable: if necessary re-adjustR55. Re-connect the fan. BANDWIDTH CHECK:BANDWIDTH CHECK:BANDWIDTH CHECK:BA

49、NDWIDTH CHECK:BANDWIDTH CHECK:Sweep the generator frequency from 20Hz to 20KHz, the output levelmust 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 wa

50、ve mode. Check the output square wave rising and fallingedge slopes: both must be 10V/S or more as shown in Fig 8.Inputs Board CheckInputs Board CheckInputs Board CheckInputs Board CheckInputs Board Check These procedures are intended for one channel at a time, repeat theseoperations for the other c