Shure_UC2_Wireless_Transmitter_Service_Manual 电路图.pdf

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1、SERVICE MANUAL CHANGE NOTICE UC2 UHF HAND-HELD TRANSMITTER Changes or corrections have been made to this service manual. Update your service manual by replacing the pages listed in the table below with the ones attached to this change notice. CHANGES EFFECTIVE DATE REMOVE these pages from your curre

2、nt manual INSERT the following revised pages attached to this notice Revision 1 ALLRevision 2 ALL Revision 2 pages:14,15,17,20,22,27,29 and 30Revision3 pages:14,15,17,20,22,27,29 and 30 SERVICE MANUAL REVISION HISTORY ReleasePart NumberDate Code Original25A1044RI Revision 125B1044SB Revision 225C104

3、4TB Revision 325C1044TK Shure Incorporated 222 Hartrey Avenue Evanston IL 60202-3696 U.S.A. UC UHF Wireless System ?1999, Shure Incorporated Printed in U.S.A. RadioFans.CN 收音机爱 好者资料库 1999, Shure IncorporatedPrinted in U.S.A. 25C1044 (TK) Service Manual UC2 Hand-Held UHF Transmitter 25C1044 (TK) Char

4、acteristics General The Shure UC2 Hand-Held UHF Transmitter is a microprocessor- controlled microphone transmitter, operating in the 692 to 716 MHz and 774 to 862 MHz frequency range. The UC2 hand-held transmitter is used in mid-level installed sound, rental, and concert sound applications. Six freq

5、uency range variations are available. Controls and Connectors 1.Mic Cartridge Grille (87 shown) 2.Battery Fuel Gauge LEDs 3.Power ON/OFF Switch 4.Audio Gain Control 5.9 V Battery 6.Battery Cup 7.Group Selection Rotary Switch 8.Channel Selection Rotary Switch Figure 1.UC2 Controls and Connectors 1 2

6、3 48 7 5 6 Service Note: Shure recommends that all service procedures be performed by a Factory- Authorized Service 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 product

7、s approvals. Contact your countrys com- munications authorities. RadioFans.CN 收音机爱 好者资料库 Shure UC2 Hand-Held UHF Transmitter 2Characteristics 25C1044 (TK) Circuit Description CONTROL PLL CONTROL MCU EEPROM (MEM) PWR. OFF DETECT +5V REG. GROUPCHANNEL SYNTH. RF POWER RF MUTERF MUTE VCO FROM BATT. UNRE

8、G. PWR. +5v AUDIO IN PWR. HOLD CIRCUIT ON / OFF SWITCH FET BYPASS TONE KEY CIRCUIT TONE CONTROL TONE KEY CALL IDBATTERY MGMT. it is controlled via the microprocessor. The tone key signal, along with the processed audio signal, is then fed to a summing amplifier, U201C. R244, at the output of the sum

9、ming amplifier, helps prevent spurious oscillations from the op-amp. After passing the ac coupling capacitor, C243, the signal is fed to the rf module via the rf choke, L207. The battery meter circuit is comprised of U205; LEDs D203, D204, D205; and various resistors. The meter works by comparing a

10、divided down version of the battery voltage (R250, R251) to two thresholds (set by R252, R253, and R254), and lighting the appropriate LED. A 9 Vdc battery provides power to the audio printed circuit board (pcb), via switch S200. FET Q203 provides electrical reverse battery protection by connecting

11、the negative battery terminal to the pcb ground only when the battery is connected with the correct polarity. The 9 Vdc then enters U203, a low dropout 5 V regulator, which gives a clean, regulated 5 V supply to run the audio circuitry. The regulator has appropriate bypass capacitors on its input an

12、d output. Q201, Q202, Q212, Q213, and their respective resistors, provide power management and timing. Shure UC2 Hand-Held UHF Transmitter 4Characteristics 25C1044 (TK) ETSI-Approved This transmitter uses the same pcb as the domestic system, but it requires a different topology and different parts.

13、A limiter is inserted between the pre-emphasis and the compressor to limit the occupied bandwidth. The buffer after the gain stage, U201A, is now an inverter with pre-emphasis and 20 dB of attenuation. Previously bypassed, the expander side of the NE575 (U202) is now activated and used as a limiter.

14、 A sample of the audio is taken from the limiter output, U202, pin 6, and sent to a control circuit that detects signals above a limiting threshold. The comparator then sends a control signal to U202, pin 5, which clamps the signal. Rf Section Processed audio enters R320, an internal potentiometer t

15、hat is adjusted for 45 kHz deviation (40 kHz for England), 100% modulation, with a 6.8 dBu 1 kHz tone at the output of the compressor. For J fre- quencies, R320 is adjusted for 5 kHz deviation with 1 kHz tone injected into the mic input, to give 23.47 dBu at U201, pin 7 (TPA4). The audio is then fed

16、 to the tuning voltage pin of the voltage con- trolled oscillator (VCO), which modulates the carrier directly. A phase locked-loop (PLL) frequency-synthesized system eliminates the need for multiplier stages and results in a much higher degree of spectral purity. The VCO is shielded to prevent exter

17、nal rf fields from affecting its operation. Regulated 5 Vdc power from the low drop-out regulator, U311, is provided to ensure frequency stability with changes in battery voltage. The VCO is capable of tuning from 782 to 806 MHz (FCC-approved), with a 1 to 4 V tuning voltage range. At the output of

18、the VCO, the rf signal splits into two paths. Frequency variations by country are given in a table in the Service Procedures section. The output of the VCO is coupled by C323 to the frequency control pin of the synthesizer, U304. The synthesizers internal circuitry divides the rf signal down, as nec

19、essary. The synthesizer contains a quartz-con- trolled reference oscillator circuit operating from a 4.0 MHz crystal, Y302, that is adjusted by trimmer C314. The transmitter output frequency is user-selectable in groups of compatible channels from 782 to 806 MHz for domestic groups. Fre- quency sele

20、ction is made via microprocessor U303, which interfaces with the user by means of the Group/Channel switches, S301 and S302. The output of the synthesizer is a series of pulses integrated by a passive loop filter (R316, C319, R317, C353, R318, C320) to produce a control voltage signal. The control v

21、oltage signal is then connected to the VCO through buffer amplifier U306B, which is used to isolate the PLL filter from the audio modulation signals. The VCO output is also coupled to the pre-driver and rf power amplifier through a resistive network (R322, R324, R325) and a coupling capacitor, C329.

22、 Shure UC2 Hand-Held UHF Transmitter Circuit Description525C1044 (TK) The pre-driver stage, Q302, provides approximately 6 to 8 dB of gain, which makes up for the pad. R326 and R327 provide base bias for the transistor, while R328 sets its operating current. L303 is an rf choke used to provide power

23、 to the stage, while L304, C332, C333, C357, and C2 provide filtering/matching for the stage. The collector of Q302 feeds into the power amplifier stage via coupling capacitor C338 and a pi-matching network made up of C339, L305, and C340. The rf power amplifier, Q304, is a dual emitter BJT. This hi

24、gh-gain, high-frequency low-noise device can provide +18 dBm out at its 1 dB compression point. It is biased via base resistors R331 and R332. Its operating current is controlled via emitter resistor R333. L306 acts as a choke, and C349, C350, C355, and C356 provide a good emitter bypass to ground.

25、The amplifier output is matched to low- pass filter U1, via L307. The low-pass filter output couples to the printed circuit board (pcb) via C347 and L308. The transmitter can deliver +17 dBm (50 mW) maximum to the antenna for domestic frequencies; JA and JB frequency transmitters can deliver +10 dBm

26、 maximum to the antenna. During transmitter power-up and frequency selection, the rf power is muted by bringing the gates of Q303/Q305 low. This provides approximately 45 dB rf attenuation until the PLL has locked. The transmitter rf is then unmuted by bringing the gates Q303/Q305 high. During trans

27、mitter power off conditions, voltage is first removed from the VCO by bringing the base of Q301 high. Thus, the carrier signal of the transmitter is not allowed to drift off frequency during power on/off conditions. Digital Section The digital section contains several circuitry blocks. Microcontroll

28、er Section The microcontroller section consists of the U303 microcontroller. The rotary switches indicate the UHF frequency group and channel. A 4.000 MHz oscillator provides the operating frequency to the microcon- troller. The oscillator circuit includes C300, C301, and Y301. U5, R306, and C305 fo

29、rm the reset circuit. U5 is the reset IC that resets the U303 microcontroller if the 5 Vdc normal operating voltage falls below 4.3 Vdc. C302 and C303 form the power supply bypass filter circuit. Memory Section The memory section consists of U302, a non-volatile, Electrically Erasable/Programmable R

30、ead Only Memory (EEPROM) that stores the Shure UC2 Hand-Held UHF Transmitter 6Characteristics 25C1044 (TK) mapping of the compatible groups and channels. The microcontroller serially communicates with this part via data and clock lines to read the frequency corresponding to the Group and Channel pos

31、ition. The ability to write to the memory occurs during factory programming only. During normal usage, this memory is used as a look-up table only. R335 and R305 resistors allow the clock and data lines to be driven independently of the microcontroller port pin states during in-circuit pro- gramming

32、 of the EEPROM. Battery Management Section The U303 microcontroller provides low battery shutdown. The shut- down threshold is 1.88 Vdc 10%. A voltage lower than the shutdown threshold on U303, pin 17, shuts down the transmitter. Resistors R308 and R309 divide down the battery voltage for U303; a ba

33、ttery voltage less than 5.65 Vdc must shut down the transmitter. This auto shutdown disables the audio tone key mix, mutes the rf output, and powers down the rf output amplifier section. The current draw from a 9 Vdc battery in this state is 14 2.0 mA, and the battery fuel gauge is not functional. T

34、urning off the power switch completely shuts off the transmitter. The audio circuit description section provides information for the battery fuel gauge circuit description. Rotary Switches for Frequency Selection A 10-position Group switch (S302) and a 16-position Channel switch (S301) select the tr

35、ansmitter frequency. Both rotary switches share the same U303 microcontroller port pins (3 through 6) for a multiplexed switch read operation. The individual switches are selected by U303, pins 7 and 8. Resistors R4, R300, R302, and R303 are the pull-ups for the switch position read. Diode packs D30

36、1 through D304 isolate the switches during the multiplexed read operation. The multiplexed scheme to read switches does not allow incorporat- ing switch change detection based on interrupts. Also, the switches can- not be constantly scanned to determine changes because the scanning frequency being i

37、n audio range is difficult to filter out. In a steady state, the switch selector common pins are inputs to the U303, pins 7 and 8, while U303, pins 3 through 6, are outputs. In this state, pins 4, 5, and 6 are held low while pin 3 is held high. This forces logic high level on switch selector pins if

38、 the switches are set on odd positions. For even position settings, the contact on pin 1 is open from the switch common pin and the internal pull-down resistors force logic low to U303, pins 7 and 8. Any switch change is comprised of state toggle from odd to even, and vice versa. Only this change is

39、 detected, and it is followed by a multiplexed switch read, in which U303, pins 7 and 8, become selectively grounded outputs to read the selected switchs state on pins 3 through 6. A multiplexed switch read is preceded by tone key and rf mutes. This mutes the audio in the receiver to allow a quiet c

40、hange to another frequency. Shure UC2 Hand-Held UHF Transmitter Circuit Description725C1044 (TK) For JA frequencies, the Group switch has 16 positions, and the Channel switch has 10 positions. Power Switch and Mute Interface When a transmitter is turned off, the PWRDN signal goes to logic low on U30

41、3, pin 19. This immediately disables the tone key, and the power hold circuit automatically kicks in to bypass the power switch. This is followed by 500 mS of delay, and then the rf is muted and turned off. The power hold circuit is also disabled at this point, and the transmitter shuts off. Shure U

42、C2 Hand-Held UHF Transmitter 8Notes 25C1044 (TK) Notes This page intentionally left blank. Shure UC2 Hand-Held UHF Transmitter Disassembly925C1044 (TK) Functional Test Verify operation and reported malfunction, referring to the product Users Guide for a description of the unit as well as information

43、 on its operation, troubleshooting, and technical data. Disassembly and Assembly ! CAUTION ! Observe precautions when handling this static-sensitive device. Disassembly 1.Remove the microphone cartridge from the UC2. 2.Use a pair of needlenosed pliers to remove the circuit board retaining ring from

44、inside the handle. 3.Push the bezel tab-snap in the handle behind the contact pcb to remove the bezel and switch actuator. 4.Slide the circuit board out by pushing on the battery connectors. Right side view of microphone Bezel Handle Tab Circuit board subassembly Tab Figure 3.Bezel Removal Contact p

45、cb Switch actuator Shure UC2 Hand-Held UHF Transmitter 10Disassembly and Assembly 25C1044 (TK) Microphone cartridge (SM58 shown) Ball screen Contact board Gain control Audio circuit board Bezel Switch actuator 9 Vdc alkaline battery Rf circuit board Gain control access Battery cup Handle Figure 4.UC

46、2 Hand-Held Transmitter, exploded view. Retaining ring Reassembly To reassemble the unit, reverse the disassembly steps given above: 1.Slide the circuit board back into the handle. 2.Reinstall the retaining ring, switch actuator, bezel, and the microphone cartridge. Shure UC2 Hand-Held UHF Transmitt

47、er Test Equipment Set-Up1125C1044 (TK) Service Procedures Measurement Reference dBu is a measure of voltage, and dBm is a measure of power. For example, the HP8903 should be labeled dBu instead of dBm because it is a voltage measurement. These two terms are often used interchangeably even though the

48、y have different meanings. Audio levels in dBu are marked as dBm on the HP8903. dB Conversion Chart 0 dBV=2.2 dBu 0 dBu=0 dBm, assuming the load = 600 Test Equipment Most test equipment needed is described in the Shure Wireless Service Equipment Manual. The following test equipment (or approved equi

49、valent) is also needed. Table 1 Test Equipment Equipment TypeModel Audio analyzer*Hewlett-Packard 8903B Digital multimeterFluke 87 Rf signal generatorHewlett-Packard 8656B Frequency counterHewlett-Packard 53181A Spectrum analyzer (domestic)Hewlett-Packard 8590L Spectrum analyzer (JA, JB)Hewlett-Packard 8591E Shure UC4 receiverShure UC4 Test headPT1840 Brass ring for use with test headPT1838Y BNC to “rocket launch” cable. For use on Japan PCB versions “N” and earlier 95C8418 BNC(male) to unterminated 50? test cablePT1824 *Audio levels in dBu are marked as dBm on