shure_t_4 电路图.pdf

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1、Shure Incorporated 222 Hartrey Avenue Evanston IL 60202-3696 U.S.A. T Wireless System ?1999, Shure Incorporated Printed in U.S.A. 2510201 (EA) SERVICE MANUAL CHANGE NOTICE T4 DIVERSITY RECEIVER Changes and corrections have been made to the Service Manual for the T4 Receiver. To update your Service M

2、anual, 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 tables below. T4 RECEIVER SERVICE MANUAL REVISION HISTORY ReleasePart NumberDate CodeColor Original25A1020

3、QGWhite Revision 125B1020SBPink Revision 225C1020SIWhite Revision 325C1020TFWhite Revision 425C1020CCWhite Revision 525C1020EARed CHANGES EFFECTIVE JANUARY 13, 2005 REMOVE these pages from the T4 Service Manual INSERT these new Revision pages into the T4 Service Manual 21 for frequencies near the to

4、p of the group, use the minimum-inductance settings. Display Check 1.Connect an external 1215 Vdc supply to the dc input (J103). The green “Power” LED should glow. 2.Check for 9 Vdc (?0.35) at TP9 (pin 3 of voltage regulator U101). Test-Equipment Settings 1.Plug into the RF generator the BNC end of

5、the 50 cable you soldered to the pcb (antenna and ground). Set the generators controls as follows: ?20 dBm on the receivers operating frequency ?15 kHz FM deviation with 1 kHz modulation 2.Activate the 400 Hz high-pass and 30 kHz low-pass filters on the audio analyzer. Shure T4 Diversity Receiver 13

6、Service Procedures25C1020 (EA) L3 L4 L5 L6 L8 L2 Y100 L11 L7 L15 L14 L13 R126 C118 L12 R41 C48 R168 U2 C145 C150 U1 R106 R16 C6 U105 U106 U103 U107 U3 U102 U108 U109 Channel A Channel B B B B B B B B B A A A A A A A A A B U101 Group designator (see Table 1) XLR audio output connector (J102) Note: Us

7、ed only on Presenter and Vocal Artist models Power input (J103) Note: Use Shure PS20 or PS20E Squelch control (R112) Antenna B Phone jack ?/?-in. (J101) Edge of case bottom Volume control Crystal (see Tables 2 and 3) “Audio Peak” (red) “Power” (green) “Diversity” (RF) (yellow) Knob U104 Antenna A D1

8、08 D109 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? (On earlier units only.) L108 L107 Note: L107 and L108 are not found on earlier units. Figure 4.Major Components Shure T4 Diversity Receiver 14Service Procedures25C1020 (EA) Coil Adjustments Each channel has to be adjusted separately. A: Channel A RF and IF 1.

9、Disconnect the power to the receiver. Mute Channel B by grounding TPB7 (pin 14 of U106). Reconnect the power. 2.Adjust the signal generators RF output so that you obtain a reading of approximately 2 Vdc at TPA4. If this is unattainable even with the full 20 dBm generator output, adjust IF coil L8 un

10、til you obtain a reading above 2 V. If you cannot get more than 1.25 V, return L8 to its preset position and adjust coil L2. 3.Adjust coils L2, L8, L3, L5, L4, and L6 (in that order) for maximum volt- age at TPA4. Use a hex tuning wrench for all adjustments except L2, which requires a non-metallic s

11、crewdriver (like a Toray driver). Reduce the generator output as required to keep the signal voltage under 3 Vdc. Perform the final adjustments with a generator output of approximately 85 dBm. Note: For coils other than L2, the “sharpness” of the tuning depends on the operating frequency within the

12、frequency group. At the upper and lower edges of a group, a distinct peak may be difficult to observe. In this case, adjust the core for maximum indication. B: Channel A Audio Note: Before making the following adjustments, power up the circuit board for at least one minute. This allows the FM detect

13、or to stabilize. 1.Set the RF signal generator for an output level of 60 dBm, a modulation of 1 kHz, and a deviation of 15 kHz. 2.Version E and later boards only: With the probe of an ac voltmeter on TPA5 (pin 8 of U105), adjust L107 for peak output. 3.Adjust R106 for 0 dBu (775 mV), ?0.1 dB, at TPA

14、5 (pin 8 of U105). 4.Reset the signal generator to its minimum output level (or “Off”). Check that both ”Diversity” LEDs turn off. 5.Set the signal generator as follows: Level: 50 dBm Ext. Modulation: 50 kHz Deviation: 15 kHz Adjust R16 for 1 Vdc (?0.5 Vdc) at TPA6 (the positive end of C111). 6.Turn

15、 off the modulation of the signal generator. Set its output to the mini- mum level, then gradually increase the level until the “Diversity A” LED turns on. This should occur with an RF input between 102 dBm and 87 dBm (typically 95 dBm). 7.Disconnect power from the receiver. Remove the jumper from T

16、PB7 and the RF input from TPA1 and TPA2. C: Channel B RF and IF 1.Make sure that the RF generator is connected to the antenna input for Channel B. Mute Channel A by grounding TPA7 (pin 13 of U106). Shure T4 Diversity Receiver 15Service Procedures25C1020 (EA) 2.Connect power to the receiver. 3.Adjust

17、 the RF output of the signal generator RF output so that you obtain a reading of approximately 2 Vdc at TPB4. If this is unattainable even with the full 20 dBm generator output, adjust IF coil L7 until you obtain a reading above 2 V. If you cannot get more than 1.25 V, return L7 to its preset positi

18、on and adjust coil L11. 4.Adjust coils L11, L7, L12, L14, L13, and L15 (in that order) for maximum voltage at TPB4. Use a hex tuning wrench for all adjustments except L11, which requires a non-metallic screwdriver (like a Toray driver). Reduce the generator output as required to keep the signal volt

19、age under 3 Vdc. Perform the final adjustments with a generator output of approximately 85 dBm. Note: For coils other than L11, the “sharpness” of the tuning depends on the operating frequency within the frequency group. At the upper and lower edges of a group, a distinct peak may be difficult to ob

20、serve. In this case, adjust the core for maximum indication. D: Channel B Audio Note: Before making the following adjustments, power up the circuit board for at least one minute. This allows the FM detector to stabilize. 1.Set the signal generator for an output level of 60 dBm, a modulation of 1 kHz

21、, and a deviation of 15 kHz. 2.Version E and later boards only: With the probe of an ac voltmeter on TPB5 (pin 7 of U108), adjust L108 for peak output. 3.Adjust R168 for 0 dBu (775 mV), ?0.1 dB, at TPB5. 4.Reset the signal generator to its minimum output level (or “Off”). Check that both “Diversity”

22、 LEDs turn off. Level: 50 dBm Ext. Modulation: 50 kHz Deviation: 15 kHz 5.Set the RF signal generator as follows: Adjust R41 for 1 Vdc (?0.5 Vdc) at TPB6 (the positive end of C140). 6.Turn off the modulation of the signal generator. Set its output to the mini- mum position, then gradually increase t

23、he level until the “Diversity B” LED turns on. This should occur with an RF input between 102 dBm and 87 dBm (typically 95 dBm). 7.Disconnect power from the receiver. Remove the jumper from TPA7 and the RF input from TPB1 and TPB2. E: Final Steps 1.If you were unable to align the unit, refer to the

24、“Bench Checks” section, which follows immediately. 2.When you have finished working on the unit, reassemble it, as described in the earlier “Reassembly” subsection on page 8. Shure T4 Diversity Receiver 16Bench Checks25C1020 (EA) Bench Checks Note: In this section, test points for Channel A are give

25、n first, and the corre- sponding test points for Channel B are enclosed in square brackets. DC Power ?Check for 9 Vdc (0.35 Vdc) at TP9 (pin 3 of U101): ?If the voltage is lower than normal (but not zero): Check for 15 Vdc at the input of U101 (pin 1), a reversed electrolytic capacitor (C152), or a

26、stage that is drawing excessive current. ?If the voltage is zero: Check for solder bridges or shorted foil traces (de- fective pcb). ?If the voltage is higher than normal or the other tests prove negative: Re- place U101. ?Check for 5 Vdc (0.25 Vdc) at TP8 (pin 10 of U3). Tuning ?First check that th

27、at the RF signal is being applied to the correct diversity channel and that the other channel is being muted with the jumper. ?If the voltage reading at TPA4 TPB4 does not vary when the RF coils are adjusted, check the operation of the local oscillator. If everything is working properly, you should

28、obtain a reading of 12 Vdc with a 95 dBm RF input signal, depending upon component parameters and receiver frequency. If you do not obtain this reading, try the following: ?With the RF generator turned off, use a spectrum analyzer to measure the injection level at TPA3 TPB3 for approximately 15 to 2

29、0 dBm. ?If the preceding level is correct, use a frequency counter to verify that the local oscillator signal is 10.7 MHz (.015 MHz) below the operating fre- quency of the receiver. Example: To receive 169.445 MHz, the local oscillator frequency should be 158.745 MHz (.015 MHz). Crystal Y100 operate

30、s at a third of this frequency, or 52.915 MHz. The nominal crystal frequen- cy, which is stamped on the part, is 3.333 kHz lower (52.911667 MHz) in this example. This discrepancy arises because the load reactance of the oscillator is not precisely zero. ?If any of the RF coils will not tune properly

31、, check for frequency-dependent capacitors that are missing or have the wrong value. If the IF coil will not tune, check C9 C52. ?If all the coils tune but the RF signal is low, compare the dc voltages and components at RF amplifier Q1 Q6 with those of a properly working unit. Muting ?With TPA7 TPB7

32、 connected to ground, the selected diversity channel should be squelched and the “A” “B” LED should be off, whether or not an RF input Shure T4 Diversity Receiver 17Bench Checks25C1020 (EA) signal is present. If you obtain different results, compare the dc voltages at U106, U107 (earlier units only)

33、, U103, and U105 U108 with those of a prop- erly working unit, or replace the pc board. ?If the muting circuit works but has insufficient adjustment range, set the RF generator for a 95 dBm signal and check TPA4 TPB4 for 12 Vdc, as de- scribed in the preceding, “Tuning,” subsection. If you get a low

34、er reading, consider the following: ?Low RF levels at the input of U1 U2 will cause inadequate noise at the output of U105D U108A. ?In order for the noise squelch circuit to function, the detector portion of U1 U2 must also be functioning properly (see the following, “Audio,” subsection). ?If necess

35、ary, check the component values and dc voltages (versus those of a known working unit) of the following: Noise amplifier U105A U108C High-pass filter U105D 108A Audio ?If there is no audio at the output of the receiver: ?To verify that the receiver is not squelched, defeat the squelch circuit by rot

36、ating R16 R41 fully CCW. There should be 9 Vdc at TPA7 TPB7, and the yellow “A” “B” “Diversity” LED should be on. ?If the preceding test does not yield the proper results, check for a prob- lem in the squelch circuitry (see the “Muting” subsection, immediately above). ?Next, check pin 6 of U1 U2 for

37、 an audio signal of approximately 15 dBV. If there is no detected audio: ?Check C1 C44 and the components connected to pins 710 of U1 U2. ?On earlier units only: Make sure that FL1 FL4 is an 86A8920 ceramic discriminator and not an 86A8910 ceramic filter, which is similar in ap- pearance. ?Check the

38、 dc voltages at U1 U2 against those of a known working unit. If no other problem is found, replace the IC. ?If audio is present at pin 6 of U1 U2 but not at the output of the receiver, trace the signal through signal amplifier U105C (TPA5) U108B (TPB5) and expander U3/U109D. When measuring at audio

39、TPA5 TPB5, use a 1 k resistor in series at the test point to prevent loading the amplifier. ?Check the Volume control (R126) and the components going to the au- dio output jack (J101). ?On vocal models, check for a signal at the Low Z microphone-level out- put, J102. If no signal is present, check U

40、109B, U109C, and associated components. ?Check the dc voltages on any stage that is not working properly; then look for wrong or missing components. Replace the ICs in the faulty stage if no other problem is found. Shure T4 Diversity Receiver 18Bench Checks25C1020 (EA) ?If you cannot set the audio l

41、evel properly with R106 R168, make sure that the other diversity channel is squelched: only one channel should be acti- vated during this adjustment. ?If you can set the audio levels properly for each channel while the other is squelched, but these levels change significantly when both channels are

42、ac- tivated, check U103. ?If the audio level is correct but the unit exhibits high total harmonic distortion (thd), vary the RF input frequency 20 kHz above and below the operating frequency. If the thd drops to an acceptable level, check the local oscillator frequency. If it is within specification

43、s, repeak the quadrature coil, L107 L108, for maximum ac output at TP5 TP8 (see step 1 of “Channel A Au- dio,” page 14 step 1 of “Channel B Audio,” page 15). On earlier units only, which do not have L107, replace ceramic discriminator FL1 FL4. ?If the audio circuitry works properly but the red audio

44、 peak LED either fails to light when the standard test signal is applied or remains on when there is no modulation, check the dc voltages at U102B, U102C, and U102D against those in a known working unit. Also check the peak LED itself. Replace any defective components. Shure T4 Diversity Receiver 19

45、Notes:25C1020 (EA) Notes: Shure T4 Diversity Receiver 20Replacement Parts and Drawings25C1020 (EA) Replacement Parts and Drawings On the next page, the parts are listed according to the designations from the pc board (see Figure 5, page 25) and the schematics at the end of this manual. Parts shown o

46、n the circuit diagram and not listed below are available through electronic-parts distributors. On the pages following the parts list are the drawings of the printed circuit boards and the schematics. Product Changes This section briefly describes significant changes to the T4. Op Amps: The older pa

47、rt for U105, U108, and U109 (manufactured by Ray- theon) was replaced. No other component changes were involved. “E” Revisions: These revisions of the pc boards temporarily changed the IF detector, deleted U107, changed a number of resistors and capacitors, made eight coils and a resistor frequency-

48、dependent, and changed Q3 and Q8 from bipolar mixers to GaAs MESFET (gallium arsenide metal semiconductor field-ef- fect transistor) mixers. FM Detector: A temporary shortage of the Sanyo chip caused the temporary substitution of a Harris FM detector. It used two additional resistors, R174 and R175.

49、 Should you replace the Harris detector with the Sanyo unit, be sure to re- move those two resistors. Frequencies: The “G” version of the pc board introduced many new Euro- pean frequencies, five additional board groups (EJ), and a consequent reas- signment of some frequencies to different board groups. The revised board re- ceived both some component changes and an altered layout. Quadrature Coil: The extensive changes on the “G” pc boards, referred to in the preceding paragraph, included the replacement of ceramic discriminators FL1 an