Shure_U4D_Wireless_Receiver_Service_Manual 电路图.pdf

《Shure_U4D_Wireless_Receiver_Service_Manual 电路图.pdf》由会员分享，可在线阅读，更多相关《Shure_U4D_Wireless_Receiver_Service_Manual 电路图.pdf（47页珍藏版）》请在收音机爱好者资料库上搜索。

1、Shure Brothers Incorporated 222 Hartrey Avenue Evanston IL 60202-3696 U.S.A. UHF Wireless System ?2000, Shure Incorporated Printed in U.S.A. 2510622 (TD) SERVICE MANUAL CHANGE NOTICE UHF WIRELESS RECEIVER MODEL U4D Changes and corrections have been made to the Service Manual for the U4D UHF Wireless

2、 Receiver. These changes will make it easier to properly align the receivers. To update your Service Manual, remove the pages identified in the tables below and replace them with the pages attached to this Change Notice. Note that there are no changes to pages not specifically identified in the tabl

3、es below. U4D SERVICE MANUAL REVISION HISTORY ReleasePart NumberDate Code Original25A1062QE Revision 125B1062QK Revision 225C1062SB Revision 325D1062TD Revision 425D1062TL Revision 525D1062AG CHANGES EFFECTIVE JULY, 2001 REMOVE these pages from the U4D Service Manual INSERT these Revisionpages into

4、the U4D Service Manual 35403540 RadioFans.CN 收音机爱 好者资料库 ?1999, Shure IncorporatedPrinted in U.S.A. 25D1062 (AG) Service Manual 25D1062 (AG) U4D Dual Diversity UHF Receiver General Characteristics The Shure Model U4D Dual Diversity UHF Receiver is a microprocessor con- trolled dual diversity receiver

5、 operating in the UHF frequency range. This product is intended for use in high-end installed sound, rental, and concert sound mar- kets. Different frequency variations are available in various countries. Controls and Connectors 5 1514 18 13 16 1717181619 15 7123 56 8910111247123684 1.MENU Button 2.

6、SELECT Button 3.RF Level Indicators 4.AUDIO Level Indicators 5.Programmable Display 6.+ Button 7. Button 8.Volume Control 9.Headphone Monitor Volume Control 10. Headphone Monitor Status 11. Headphone Input Connector 12. POWER On/Off Switch 13. Power Input Connector 14. Power Output Connector 15. Ant

7、enna Input Connectors 16. HIGH Z (Unbalanced) Output Connector 17. Mic/Line Slide Switch 18. LOW Z (Balanced) Output Connector 19. Networking Interface Figure 1.U4D Receiver Controls and Connectors Service Note: Shure recommends that all service procedures be performed by a Factory-Authorized Servic

8、e Center or that the product be returned directly to Shure Brothers Inc. Licensing: Operation may require a user license. Frequency or power-output modifications may violate this products approvals. Contact your countrys communications authorities. RadioFans.CN 收音机爱 好者资料库 Shure U4D Dual Diversity UH

9、F Receiver 2 25D1062 (AG) Circuit Description Circuit Description Power Section The receiver accepts power line voltage ranging from 85 Vac to 264 Vac. The receiver hardware uses the +5 Vdc, +12 Vdc and 12 Vdc volt- ages from the switching power supply. The switching power supply has 40 W overall ou

10、tput power capability, with maximum current capabilities of 4A at 5V, 2A at +12V, and .5A at 12V. It also includes a fastacting 2.5A fuse. Up to four in-line rf amplifiers may be connected to the receiver, depending on system setup. The receiver provides dc power to the in- line amplifiers via the B

11、NC antenna ports and RG58 cables. Maximum dc power supplied to each antenna port is limited by selfresettable fuse. Rf Section The rf circuit description is limited to one rf strip (channel A) in receiver 1. The other rf strip (channel B) is virtually identical. The local oscillator (LO) section is

12、common for both channels and is described separately. Receiver 2 is identical to receiver 1. The rf input signals are sent from the antenna ports to the receiver via cables with BNC and rf miniplug connectors. Antenna port A is con- nected to J302 of receiver 1. Antenna port B is connected to J302 o

13、f receiver 2. Connectors J302 on each receiver are the input of the rf power dividers. Each of these splits the rf power from the antenna between two receivers. The outputs of the power dividers are connected to the inputs of the opposite rf strips of the other receiver: J303 of receiver 1 to J304 o

14、f receiver 2; and J303 of receiver 2 to J304 of receiver 1. In addition, J306 on receiver 1 and J306 on receiver 2 have to be solder jumpered to provide connection from the outputs of the rf power dividers to channel A rf strips of both receivers. Rf Channel The rf signal is preselected to the appro

15、priate frequency range with two dielectric filters. The first dielectric filter is located between the antenna port and the low noise amplifier (LNA). The second filter is located between the LNA block and mixer input. The front end down converter integrated circuit contains the LNA block and the fi

16、rst mixer. The first conversion produces the first intermediate frequency (IF) signal at 50 MHz. The first if signal is amplified with the MMIC, band- limited with a SAW filter, then down-converted to the second IF frequen- cy (10.7 MHz) with a second down-converter. The second down-converter has an

17、 internal second local oscillator (LO) that oscillates at 60.7 MHz, using an external crystal. The second LO buffered output also provides the LO drive to channel B of the sec- RadioFans.CN 收音机爱 好者资料库 Shure U4D Dual Diversity UHF Receiver 325D1062 (AG)Circuit Description ond mixer. The second downco

18、nverter also incorporates an internal IF amplifier that is used with external 10.7 MHz ceramic filters. The 10.7 MHz signal goes to the second IF gain block with detector. The audio output is buffered with an operational amplifier, then processed as de- scribed in the Audio section. The noise output

19、 is also amplified by the operational amplifier, providing a signal for the noise squelch circuitry. The received signal strength indication (RSSI) output of LM1865 is used to drive the LEDs on the receiver front panel. Local Oscillator The first local oscillator (LO) is common for channel A and cha

20、nnel B rf strips. The LO is a phase locked-loop (PLL) system. The PLL consists of a prescaler/synthesizer, voltage-controlled oscillator (VCO), loop filter, rf power divider, and band-pass filter, band limiting the LO signal before injection to the first down converter. The prescaler receives the rf

21、 signal from the VCO via the coupling capacitor, C116. The output from the phase detector is connected to the external loop filter, which controls the tuning voltage input to the VCO. The prescaler/synthesizer integrated circuit (IC) is a serial program- mable input IC. It receives the programming d

22、ata from the front panel/ digital board. The digital board includes a user-controlled microprocessor that allows users to change the frequency and other settings. Audio Section The audio for channel A comes from the channel A detector output of the rf section. Each channels audio then enters its own

23、 factory-adjust- able gain amplifier stage. These adjustable gain stages are used to exactly match the audio levels coming from each rf channel, as well as to set the proper level necessary for the compandor. From the gain stages, each channel enters an analog switch. Noise outputs also come from th

24、e channel A and channel B detector outputs. Each noise output enters a bandpass noise filter that is used to measure the 60 kHz noise present in the audio signal. The noise level is propor- tional to the signal-to-noise ratio of the channel. The noise from a channel, after being rectified and low-pa

25、ss filtered (changed from an ac to dc signal), enters a bank of comparators. A ver- sion of the channels noise that is 6 dB less also enters the comparator bank. The noise levels from the two channels are then compared. If they are within 6 dB of each other, the comparators send a logic high signal

26、to the control of each channels analog switch, and audio is allowed to pass through the switches. If the noise levels are not within 6 dB of each other, the channel with the noise level greater than 6 dB of the other channel is not allowed to pass through the analog switch; the comparator puts a log

27、ic low signal on the control line for the analog switch. Also, each channels noise is Shure U4D Dual Diversity UHF Receiver 4 25D1062 (AG) Circuit Description compared to an adjustable squelch level (a dc level). If either channels noise is greater than the squelch threshold, its switch is shut off.

28、 The outputs from the analog switches are connected at the audio combining stage. This is a unity gain buffer stage where the audio from channel A is combined with the audio from channel B. The output from this stage splits into three paths. The first path goes to a high Q tone key detection circuit

29、. This circuit is a crystal filter in which the tone key level is converted to dc and compared to a fixed dc voltage. If the tone key is not present, the comparator sends a logic high signal to an audio mute IC and mutes the receiver output. If the tone key is present, a logic low signal is sent, an

30、d the audio is allowed to pass. The second path goes to a low Q bandpass filter centered around 32 kHz. This filter provides low battery detection in the receiver. The lower Q allows for small frequency variation of tone key from various transmitters, without large amplitude variations that the crys

31、tal filter would have. The filtered signal is then rectified and averaged. The resulting dc signal is amplified and then enters the digital section of an analog to digi- tal (A/D) converter. The A/D converter and the microcontroller control the battery icon on the LCD display. The third path goes in

32、to the compandor, via a 17 kHz low-pass filter. Here the audio is expanded and de-emphasized. The compandor output then goes off the audio board to a volume potentiometer on the front panel board. Then the wiper is brought back to the audio board. At this point, the audio signal takes two paths. The

33、 first path is through the mute IC and into the output stage. The output stage consists of an inverting amplifier stage, the output of which goes directly to one pin of an XLR connector. A 180 phase-shifted version of the same sig- nal is obtained by tapping off of this point and entering another in

34、verting stage. This phase-shifted version then goes to another pin on the XLR connector. Taking the output across the two XLR pins provides an electrically balanced output signal. The unbalanced output is obtained by taking one of the output stage amplifiers outputs with respect to ground. Each side

35、 of the balanced output goes through a pad that is switched in or out by the user. This switch changes the balanced output level by approximate- ly 30 dB. The second path is through the headphone amplifier circuit. The audio signal goes into a fixed gain amplifier, then off the board to the monitor

36、board. The monitor board can select between receiver 1 and receiver 2. It also has a user-adjustable gain control, and a 1/4 inch jack for headphones. For the audio level meter, audio is tapped off from the 17 kHz filter output and goes through a full wave precision rectifier and averaging cir- cuit

37、. This dc signal then enters a dc amplifier stage to adjust levels for Shure U4D Dual Diversity UHF Receiver 525D1062 (AG)Circuit Description the LEDs. The output from this stage drives the audio level meter on the front panel board. A dc voltage from the detector chip RSSI drives the bar graph inte

38、grated circuit on the front board for the rf level meters. Display Board / Digital Section Microcontroller Section The microcontroller section consists of microcontroller U103 and the liquid crystal display (LCD). The microcontroller has an on-board LCD driver. R104, R116, and R118 supply the microc

39、ontroller with LCD drive voltage for a four-plex drive. The LCD is a transmissive type that uses a backlight for optimum readability. J104 supplies current, limited through 5 (paralleled R119 and R120), +5V for the LCD diffused backlight LED array. The LCD indicates frequency in MHz, a user-programm

40、able name up to 8 characters long, and the UHF frequency group, channel, and television channel. The LCD also has a battery fuel gauge that indicates the state of the transmitter battery. A padlock icon on indicates whether the user- accessible menus are locked or unlocked. A 4.000 MHz oscillator (Y

41、101) provides the operating frequency to the microcontroller. The oscillator circuit includes C107, C108, R111, R112, and Y101. R105 and C103 form the reset circuit. R121 is the pull-up resistor for the U103 programming voltage pin. Memory Section The memory consists of non-volatile ferroelectric RA

42、M or EEPROM U106, which stores current receiver settings and maps of compatible groups and channels. R108 and R109 allow in-circuit programming of U106 FRAM. Analog to Digital Converter Section The analog to digital converter section consists of A/D converter U101. Signal DLOW_BATT (P102.2, U101.2,

43、I138) from the audio sec- tion is an analog signal representing the transmitters battery level. This is converted to an 8-bit digital signal for the microcontroller and is dis- played on the LCD as the battery fuel gauge. Microcontroller U103 communicates serially with A/D converter U101. Shure U4D

44、Dual Diversity UHF Receiver 6 25D1062 (AG) Circuit Description User Interface Section The user interface section consists of switches SW101 MENU, SW103 SELECT, SW102 UP (+), and SW104 DOWN (). These switches provide access to various user-programmable menus on the front panel display. The LCD provid

45、es the user with feedback for all switch actions performed. Audio Output Level Control R110 The audio output level control potentiometer has no associated circuitry in this section. Refer to the Audio Section. RSSI Bar Graph Section Channel A Bar graph driver U104 gets the DRSSI_CH_A analog signal (

46、U104.5, P102.6, I155) from the rf-audio board and indicates its strength on the 5-LED bar graph formed by D117, D115, D110, D109, and D105. Channel B Bar graph driver U102 gets the DRSSI_CH_B analog signal (U102.5, P102.11, I170) from the rf-audio board and indicates its strength on the 5-LED bar gr

47、aph formed by D116, D114, D111, D108, and D106. Audiometer Bar Graph Section Bar graph driver U105 gets the DAUDMTR audio metering (averag- ing only, no peak) signal (U105.5, P102.13, I156) from the rf-audio board and indicates its strength on the 7-LED bar graph formed by D119, D118, D113, D112, D1

48、07, D104, and D103. Diversity LEDs D101 and D102 Diversity LEDs A and B have no associated circuitry in this section. Refer to the Audio Section. Digital to Analog Converter Section The microcontroller communicates with 8-bit serial D/A converter U215 over two signal wires, DSQUELCH (P102.3, U103.10

49、, TP113) and DSCL (P102.15, U103.9, T114), to set up the audio squelch threshold. Shure U4D Dual Diversity UHF Receiver 725D1062 (AG)Circuit Description Display Board Interconnect with Rf-Audio Board Integrated ribbon cable connector P102 interfaces with the rf-audio board and the networking Interface board through the display board. Pin assignments for the P102 connector are presented in the table below. Table 1 P102 Interconnect Pin Assignments PIN NO.SIGNAL NAMEDESCRIPTION 1D+5V+5V power supply to the Digital Board 2DLOW_BATTAnalog voltage representing TX battery level 3DSQUELCHDat