Philips-LX-3950-W-Service-Manual(1) 电路图 维修手册.pdf

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1、CLASS 1 LASER PRODUCT Service Manual Service ServiceService ServiceService LX3950W/01 TABLE OF CONTENTS Page Location of pc boards fr Reparaturen sind Original-Ersatzteile zu verwenden. Sicherheitsbauteile sind durch das Symbol ! markiert. I Le norme di sicurezza esigono che lapparecchio venga rimes

2、so nelle condizioni originali e che siano utilizzati i pezzi di ricambio identici a quelli specificati. Componenty di sicurezza sono marcati con ! GB After servicing and before returning set to customer perform a leakage current measurement test from all exposed metal parts to earth ground to assure

3、 no shock hazard exist. The leakage current must not exceed 0.5mA. 2-12-1 DISMANTLING INSTRUCTIONS Dismantling of the DVD Loader 1) The tray can be manually open by inserting a minus screw driver and push the lever in the direction as shown in Figure 1 to unlock the tray before sliding it out. 2) Sl

4、ide out the tray and remove the Cover Tray assembly (pos 110 + pos 111 + pos 112) as shown in Figure 2. 3) Loosen 5 screws to remove the Cover Top (pos 240). - 1 screw each on the left R = 400Hz, via input leveltestpoint Input and Measurement ground AC VoltmeterFrequency counter F117410 mV L F118410

5、mV R F117410 mV L F118410mV R F117410 mV LF145210 mV 20 mV F118410mV RF144210 mV 20 mV F117410 mV L F118410mV R F117410 mV L F118410mV R F1172100 mV L F1182100 mV R Check RF output signal LF input signal L = 400Hz; R = 400Hz, via input levelInput groundchannel Measurement RF ground Output signalFreq

6、uency counter Version F1170 mV L864.5 0.025 MHz for EUR and UK version F1180 mV R915.3 0.025 MHzfor USA version Alignment of the modulation level * Method 1 LF input signal L = 400Hz; R = 400Hz, via input levelinput ground Connect RF Modulation Analyzer to testpoint Measurement ground Align RF Modul

7、ation Analyser deviation F117410 mV L F118410 mV R Method 2 LF input signal L = 400Hz; R = 400Hz, via input levelinput ground Connect AC mV meter to testpoint Measurement ground AlignAC mV meter F117410 mV L F118410 mV R * or Method 1 or Method 2 to be applied 4 DC Check F116F115F114 F116 F116 205 m

8、V 20 mVF149 F149380 mV 40 mV F147200 mV 20 mV 23.4375 kHz 10 Hz 46.875 kHz 20 HzF131 F130 50 kHz 3 Hz 80mV rms (= 230mV pp) 3179F115F116F114 F116F150F1163179 wireless receiver test circuit 68 E 50 E 68 E To RX input RF Generator DUT LF Voltmeter e.g. PM2534 CL36532008_020.eps 170403 Powersupply chec

9、k Measurement groundtestpointScope / Voltmeter F702+10V 0.1V F740+ 5.2V 0.5V F705+ 8V 0.5V F707+ 8V 0.5V F708+3.6V 0.2V F709+7.75V 0.5V F744F740+ 5.2V 0.2V F712+ 4.1V 0.3V F713+ 4.1V 0.3V Functional check picture: receiver test circuit: RF input signal, modulation = 50 kHz via adaptation network* RF

10、 carrier frequency Input signal channel switch select Output signalVoltmeterversion F748863.3 MHz1 mV rmschannel 1F728LF output for EUR and UK version F748914.1 MHz1 mV rmschannel 1F728LF outputfor USA version Alignment of the receiver EUR version RF input signal, modulation = 50 kHz via adaptation

11、network* RF carrier frequency Input signal Testpoints grounded to F744 channel switch select AlignmentAlignOutput signalVoltmeterversion F748863.3 MHz1 mV rmsF724 when no audio on one of the inputs 0.1 V for a period of 4 minutes then the Processor shuts down the modulation of the TX transmitter (LE

12、D off) Tx in off mode: (TX transmitter powered, no modulation and LED off) Start of the modulation and LED on by applying minimum 0.1Vrms on left or right input Frequency response: Response is flat (+/- 1.5dB) between 100Hz and 15kHz for both channels One channel-input is built up by using an audiot

13、rafo to make the coupling towards source (LX3750 Home cinema DVD player with incorporated class D amplifiers) This causes a difference in f-response especially for low frequencies below 100Hz for left and right channel, however not audible in its application. Input impedance: 1 K ohm Led-functionali

14、ty: built in led indication: Red = ON, power on, transmitter active Red = OFF, power on, no modulation Audio-input section: The right audio input channel is different from the left input: left uses a low cost audio transfo, since there has to be a complete separation between the left and right speak

15、er outs of the DVD player LX3750. Of course this gives a small difference in frequency response, but absolutely not audible in its application. Pin 4 is connected straight to one output pin of the DVD speaker out: this to have a “reference - ground”. Input impedance for both channels is always below

16、 1Khz, making the unit immune for all kinds of interferences on the speaker lines. The rather high input levels (up to 20V rms /each channel) are conditioned and brought to a level of nominal 0.42 Vrms on pin 1 and 3 of 1120. This 0.42 Vrms gives 50Khz FM deviation in the transmitter. Extra protecti

17、on is established by the fast diodes 6142 and 6144. DC-reference is made by 3115-3116 and 2116. A 23Khz notch filter 5115 / 5120 is built in to avoid interfer- ences with the used pilot frequency of the transmitter. Audio detector: A part of the audio info is fed to the audio detector built up aroun

18、d 7101-A and 7101-B. Basically its a two-stage amplifier with a very high gain factor (3135/3133 and 3136/3134). A square signal has to be found on the output of 7101-A. This block-wave is fed to the rectifier/ integrator around 6130. In normal operation 7135 is always conducting, pulling down the l

19、evel on the trig-input of the microprocessor 7145. As long this input is low the connected transmitter is enabled by the microprocessor. When no audio input, the trig input comes high (5V), and the internal timer of the processor counts down till 4 minutes have past away. After this four minutes (ap

20、prox.) the transmitter will be disabled = no modulation and red led off. A very low audio input “trigs” the processor and the transmitter starts up again. (Led = red). Four-channel selection is done by 2 lines (LSB - MSB) on the processor. Power supply: The unit operates on a 14 Vdc mains power adap

21、tor: 12Vdc, mainly for the transmitter, is furnished by 7100 -L4931CDT120, which is a low drop regulator. The 5 Vdc for the PIC is made by the HT7550 low power regulator. 1.8.2.Wireless System GENERAL INTRODUCTION The wireless system is intended for stereo sound in the range from 20 Hz to 20 kHz. It

22、 can be used for normal L/R stereo sound or for the surround channels in Dolby systems. The system has an analogue sound processing system (companding expanding) and uses synthesised tuning at both the transmitter and receiver side. There are frequency executions available in different frequency ban

23、ds: 433 MHz (some EU), 864 MHz (EU) and 914 MHz (US). In each particular frequency band, there is a choice between 4 different channels or frequencies. SYSTEM CONSIDERATIONS The Wireless system uses a very high performance audio processing that allows up to 100 dB dynamic range to be transmitted ove

24、r a classic analogue link. Through the companding effect at the transmitter (reducing the dynamic range by a factor of 2 in dB) and by an expanding effect in the receiver (increasing the dynamic range by a factor of 2 in dB). In addition the system has the possibility to maintain the high S/ N up to

25、 low RX fieldstrengths by applying sliding stereo (this means reducing the stereo effect at low signal fieldstrengths) Pre-emphasis (at TX) / de-emphasis (at RX) technique is with15 S time constance. Since the signal processing is analogue, there is a low latency in the system of 15 S between input

26、TX and output RX. The receiver part has a power save mode that will be initiated automatically when no signal to reduce power consumption. The system uses normal FM modulation / demodulation and also uses the Zenith stereo principle. However, the frequencies used are different in this respect: Subca

27、rrier freq. = 3 * 15625 Hz = 46.875 kHz (chosen because interference zero-beats with the TV line freq). Consequently the pilot freq. is 23.4375 kHz (half of subcarrier). TRANSMITTER The block diagram of the transmitter is as follows: CL36532008_069.eps 220403 TRANSMITTER R B14B 1101 1 2 7113 NJM4565

28、M 7112 SA572D 3 G 1 7 6 5 5 11 RECTI- FIER R L L R 2 3 32 5 6 TO TV CONNECTION TO1103 7 8 +8V +5V PD 7119 6105, 7118 4 I2C-CLOCK POWER DOWN DETECTOR I2C-DATA 7117 LD1117DT 11V_S F124 F140 F141 F145 F144 F131 F149F147 F113 F110 F114 F130 F126 7 7110 74HC4060 OSCILLATOR ENABLE (Low) 256 512 PRE-EMPHAS

29、IS - COMPANDER - STEREO ENCODER - - PLL - MULTIPLEXED 2165, 3160, 3190 2166, 3161, 3191 PRE-EMPHASIS 9 3 13 12 VPIL 3 5 62 1 16 5 14 7 9 8 2 SDA I2C-DATA I2C-CLOCK SCL VERSION SELECTION 433MHz or 864MHz 6 11 ADC 1105 4MHz VPIL VFIL (ENABLE) +6V 3105 3106 31796102 BB151 (VARICAP) 7102 OSC VOSC (ENABL

30、E) X2 (ENABLE) 7103 BFR92A 7104 7105 5112 +8b 7101 TSA5060A MPX MODULATION LEVEL ADJ. 3 5 7111 74HC4053HD 7116-B NJM4565M 7116-A 4 7 3174 3177 V 9 SUBC 46,875kHz 6 LIMITERLOW-PASS LOCAL OSCILLATOR FREQUENCY MULTIPLIER FILTER OUTPUT 7106 BFG520 SYNTHESIZER 14 13PILOT23,4375kHz PD 10 11 1106 12MHz V V

31、 V X2 Figure 1-7 Block diagram transmitter interface Figure 1-8 Block diagram transmitter 11-2211-22 Synthesiser and local oscillator The internal circuitry of the TSA5060A can be seen in below figure The TSA5060A is software controlled by the I2C bus. TV applications do send commands directly via t

32、he TV slow bus while the audio applications have a small interface board with an P PIC12C508 to send the commands. To verify whether there is communication between the host device and the TSA 5060A one can check the supply voltage of the osc.transistor 7103 (TP F113) and should be about 7.5 V in nor

33、mal conditions when the I2C signal is interpreted by the synthesiser. If there is improper communication the voltage remains at zero V. There is version recognition foreseen to discriminate between 433-864 and 914 MHz units. This feature will automatically load the correct frequency division words i

34、nto the synthesiser at starting up and initialisation of the host device (e.g. TV set). The reference quartz is 4 MHz and is divided down to a lower reference frequency of 25 or 50 kHz (depending on the version). The PLL filter is passive and includes 2103 2104 3107. The transistor 7102 is part of t

35、he PLL current source and allows connection to higher supply voltages as +5V. The TSA5060A has some output ports that are used to: Vosc (to switch the LO) Vpil (to switch the pilot) Port P1 to switch the PA The oscillator (LO) is a common base transistor (7103) that is oscillating at half the output

36、 frequency. The frequency is tuned by the varicap 6102 until the tuning voltage is in the range of the loop filter (between 1 and 6 Vdc). If the voltage is outside this range then possibly the division ratio is chosen outside the normal range or some freq. dependant component around the transistor i

37、s faulty. Multiplier and power amplifier The LO signal is multiplied by two in a separate stage 7105 in order to get a high isolation between the LO and the antenna. There is quite some filtering necessary at the output because it is necessary to suppress the half freq, and its harmonics from reachi

38、ng the PA stage. There is 2 stage bandstop filter followed by an elliptic low pass filter. This filtering has to do with the legal requirements for spurious radiation. The PA stage with 7106 increases the power level to about +15 dBm at the output of the filter. The transistor is polarised into clas

39、s A for min. harmonic content and furthermore there is output filtering available to further reduce the harmonics. The configuration differs with the freq. version. The 864 and 914 MHz versions for TV sets are using an integrated antenna on the board while the 433 TV version and all AV versions use

40、a telescopic antenna. This results in different matching networks between TX and antenna. The printed dipole is driven symmetrically by a balun for optimum power transfer and symmetry. There are protection diodes (6110 the class D keeps on oscillating, the led stays green but no sound is produced on

41、 the outputs. The control line STBY_OUT (connector 1107-pin 3) to the power supply stays low. When the receiver goes into powersavemode (= after 10 minutes no signal from the AV set), STANDBY signal is high; then the circuitry around 7107 pulls down the mode line of the amplifier to nearly 0V via th

42、e MUTE_AMPn signal. (Note that the mute line from the receiver is also high under this condi- tion). The amplifier is completely in standby mode, the oscillator in amplifier IC 7101 stops and all internal references are disabled. The led red will be on, while green is off. At the same moment transis

43、tor 7106 is not saturated anymore and the control line towards the switched mode power-supply becomes high. This switches off the main +/- 29.5Vdc supply and the whole unit comes in a real power save mode. 7112 helps to pull down the +/- 29.5 Vdc main supply: Will be switched off when the unit goes

44、into power save-mode. See circuitry around 7107 and 7106. + 10Vdc receiver supply: Is always present, receiver stays always active Note that all supplies have the same ground reference. Mute circuitry: In normal operating circumstances, the voltage on the- “mode” pin of the amplifier IC7101 will be

45、4V5. This is the MUTE_AMPn signal. mute line of the amplifier-chip 7101 as fast as possible to avoid plops at this transition. When the receiver detects a valid signal from the AV set, this power-save-line becomes continuously low, and after a small time (2152, 3143, 3147), 7104 is off. At the same

46、moment the mute line becomes low and the amplifier is enabled again. Also the control line (connector 1107-pin 3) to the power supply becomes low, thus starting up the main +/- 29.5 Vdc supply Amplifier The amplifier TDA8920TH operates on +/-29.5 Vdc and can deliver 2 x 50 Watts into 8 ohm loads. Us

47、ing the very efficient class D - technology, it minimizes the dissipation. The class - D chip runs on a 300kHz oscillator, therefore a 12dB / octave output filter is needed (coil 5104 and 5105, and capacitor 2122 and 2125). Input signals are 180 phase shifted by 7100-C and 7100-D, ( the effect - spe

48、akers have to be in phase with left and right main speakers, otherwise bass reproduction will be poor) Input signals are filtered in the two-section high pass filter around 7100-B and 7100-A. The 3 dB point is somewhere around 30Hz. Input sensitivity of the amplifier for maximum output: typical 1.4V

49、 rms Figure 1-26 Microcontroller functions Figure 1-27 Block diagram amplifier Figure 1-28 Mute ampn circuit AUDIO OUTPUT AMPLIFIER W 1106 R R L L +10V MUTE 3117 7110 MUTE WIRED POWERSAFE 1 2 3 5 1 1109 WIRED AUDIO IN (3,5MM stereo jack) 3 2 GREENRED 6109 5 F135 6 7 4 7100-D,7100-A 7101 TDA8920 7104 MUTE CONTROL ON LED DRIVER STANDBY LED DRIVER 3126 8 Ohm/50W 8 Ohm/50W sensitivity 1.4Vrms sensitivity 2.5Vrms (active high) (active high) 3144 +10V 4 3 2 1 Temperature protection Mode mute OSC 5104,2122 5105,2125 Input Input Driver Driver 7100-C,7100-B +