Shure T 4 wireless receiver Service manual
The Shure T T4 is a single-channel, crystal-controlled unit that operates within the 169 MHz to 238 MHz VHF-FM band. It features diversity reception of signals entering via two independent RF sections, each with a single-element, quarter-wave antenna.
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Shure Incorporated 222 Hartrey Avenue Evanston IL 60202-3696 U.S.A. T Wireless System 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 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 tables below. T4 RECEIVER SERVICE MANUAL REVISION HISTORY Release Part Number Date Code Color Original 25A1020 QG White Revision 1 25B1020 SB Pink Revision 2 25C1020 SI White Revision 3 25C1020 TF White Revision 4 25C1020 CC White Revision 5 25C1020 EA Red CHANGES EFFECTIVE JANUARY 13, 2005 REMOVE these pages from the T4 Service Manual INSERT these new Revision pages into the T4 Service Manual 21 & 22 21 & 22 E1999, Shure Incorporated 25–1020–1 (EA) Printed in U.S.A. ® Service Manual 25C1020 (EA) T4 Diversity Receiver Characteristics General This manual tells how to service and align the Shure T4 Diversity Receiver (Figure 1). This single-channel, crystal-controlled unit operates within the 169 MHz to 238 MHz VHF-FM band. Á Á ÁÁÁÁÁÁÁÁÁÁ ÁÁ Á Á ÁÁÁ Á ÁÁ ÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁ ÁÁÁ ÁÁ ÁÁ ÁÁ Á ÁÁÁÁÁÁÁÁÁÁ Á Á Á ÁÁ Á Á Á Á ÁÁ Á ÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁ ÁÁ 1 2 DC INPUT T4G SQUELCH MIN MAX 12-18 VDC 9 1 2 DC INPUT SQUELCH T4V 3 12-18 VDC MIN MAX 3 4 5 6 7 8 Figure 1. Controls and Connectors 1. “DC Input” jack 6. “Audio Peak” LED 2. Squelch control 7. Volume control 3. Antennas 8. Audio “Output” (1/4Ȃ phone jack) 4. “Power” LED 9. “Balanced Low Z” audio output (XLR) 5. “Diversity” LEDs E1999, Shure, Inc. Printed in U.S.A. 25C1020 (EA) 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. 1 Characteristics Shure T4 Diversity Receiver Circuit Description The Shure Model T4 is a single-conversion superheterodyne diversity FM receiver operating in the 169–238 MHz band. It is intended for use with the matching Shure T Series wireless transmitters. RF Stages Two complete, independent RF sections provide diversity reception. Signals enter via the single-element, quarter-wave antennas. Channel A: The signals pass through a double-tuned filter (L3 and L4) before entering MOSFET amplifier Q1. The output of this stage is double-tuned by L5 and L6, which also provide impedance-matching to Gate 2 of GaAs MESFET (gallium arsenide metal semiconductor field effect transistor) mixer Q3. Gate 1 receives the local oscillator signal from transistor Q5. A third-overtone quartz crystal in the 50–70 MHz range provides frequency control. The collector circuit of the oscillator is tuned by L8 to the third harmonic of the crystal (160–230 MHz) to provide the proper injection frequency for a 10.7 MHz intermediate frequency (IF). Channel B: This channel is identical in design to channel A. The signals from the antenna pass through a double-tuned filter (L12 and L13) before entering MOSFET amplifier Q6. The output of this stage is double-tuned by L14 and L15 and fed to Gate 2 of GaAs MESFET mixer Q8. Gate 1 receives the local oscillator injection from buffer transistor Q4, which is tuned by L7. The buffer stage helps isolate the diversity channels from one another by preventing crosstalk through the common local oscillator section. IF and Audio-Detection Stages Channel A: L2 tunes the output of mixer Q3 to 10.7 MHz before the signal enters ceramic filter FL3. Transistor Q2 provides IF amplification to make up for the losses in the filters. After passing through a second IF filter, FL2, the signal enters amplifier/detector U1. The detected audio from pin 6 is amplified by U105C. Channel B: L11 tunes the output of mixer Q8 to 10.7 MHz before the signal enters ceramic filter FL6. Transistor Q7 provides IF amplification before the signal passes through the second ceramic filter, FL5, and enters amplifier/detector U2. The detected audio from pin 6 is amplified by U108B. Noise-Operated Squelch A noise-operated squelch system provides both diversity-channel selection and muting. Noise signals are obtained from the additional detector outputs at pin 7 of U1 and U2. Noise Signals Channel A: The squelch level control (R16) adjusts the noise signal from U1 before it is amplified by U105A. Active high-pass filter UI05D removes audio components that could cause false triggering. The noise is then rectified by D101 and smoothed by C111 to provide a dc voltage that varies with the amount of noise present on the detected signal. Characteristics 2 25C1020 (EA) Shure T4 Diversity Receiver Channel B: This follows an identical scheme: noise signals from U2 are adjusted by squelch level control R41 before being amplified by U108C, filtered by U108A, rectified by D107, and smoothed by C140. Comparator Circuits U106C and U106D compare the dc noise signals from the two channels. When these signals are comparable, U106C and U106D direct analog switches U103C (Channel A) and U103B (Channel B) to allow both channels to pass through. The signals from each channel are correlated while the noise is uncorrelated, which makes possible a theoretical signal-to-noise improvement of 3 dB. When the dc noise signals are not comparable, the channel with less noise is chosen. U106A imposes an additional criterion on Channel A, and U106B does the same for Channel B. Each channel’s dc noise voltage is compared to a threshold set by user-adjustable R112 (Squelch). A channel whose noise exceeds this threshold is squelched. If both channels exceed their thresholds, the audio output of the receiver is squelched. Squelching is accomplished by tying together the outputs of U106A and U106C (Channel A) or U106B and U106D (Channel B). These outputs also control the yellow “Diversity” status indicators. Comparator U102 provides additional attenuation in the squelched state by shutting off compandor U3. Audio Output The audio signals from the two channels pass through analog switches U103C and U103D, are buffered by U109A, and enter U3, which provides a 2:1 logarithmic expansion. An additional IC amplifier (U109D) operates in conjunction with U3 to provide a lower noise floor. The output of this stage passes through the Volume control (R126) to the “Output” connector (J101). A bridging amplifier formed by U109B and U109C provides the “Balanced Low Z” output. “Peak” LED This red indicator warns the user when the transmitter deviation is approaching the limit of 15 kHz. This function is implemented by a window comparator (U102C and U102D) and a pulse stretcher (U102B) that makes short transients more visually apparent. Power The green “Power” LED indicates when the external power converter (or a battery pack) is supplying power to the receiver. The circuitry operates normally with an input of 12–18 Vdc. D10 provides reverse polarity protection, and U101 supplies voltage regulation. The “Dc Input,” audio “Output,” and “Balanced Low Z” output connectors are filtered to prevent local oscillator radiation from the cables. 25C1020 (EA) 3 Characteristics Shure T4 Diversity Receiver Notes Notes 4 25C1020 (EA) Shure T4 Diversity Receiver Preliminary Tests Listening Tests Before disassembling the unit, operate it to determine whether it is functioning normally. First and most important: Review the customer’s complaint (if available) and focus your tests on the problem. If this proves inconclusive or you want somewhat more extensive checks, perform the following functional tests. Functional Tests The following tests require partial disassembly of the unit: RF Test The following is the best “fast” test of a receiver’s RF performance. A receiver that passes this test can be removed from the list of suspects for any “dropout” or “range” problem. Initial Set-up 1. Set the receiver’s Squelch control to its middle position and the Volume control to its maximum position. 2. Set the RF signal generator to the receiver’s frequency. 3. Remove the receiver’s antenna (see “Disassembly,” page 7). Plug the BNC end of the 50 Ω test cable into the RF signal generator. Tack-solder the cable’s center conductor to the receiver’s antenna input (TPA1 or TPB1), and the shield to a ground plane as close as possible to the antenna input (TPA2 or TPB2). Test 1. Connect power to the receiver and turn it on. 2. Verify that the unit unsquelches with RF signals greater than –89 dBm. 3. When the unit unsquelches, verify that the “Diversity” LED glows. Audio Tests Initial Set-up 1. Set the RF generator as follows: Level: –60 dBm Deviation: 15 kHz Modulation: Ext 2. Set the audio analyzer as follows: Amplitude: 1.4 Vrms Frequency: 1 kHz 3. Using a 3.3 kΩ load, connect the receiver’s unbalanced audio output to the input of the audio analyzer, and engage the 400 Hz and 30 kHz fil- 25C1020 (EA) 5 Preliminary Tests Shure T4 Diversity Receiver ters. The receiver’s Volume control should still be in its maximum position. Tests 1. Verify the following receiver measurements: S Audio level is 400 mVrms, "90 mV. Record your measurement as a reference level for the next two steps. S Thd is <0.75%. 2. Change the audio analyzer’s frequency to 100 Hz, and disengage the audio analyzer’s 400 Hz filter. Verify that the receiver’s unbalanced audio output is within +2 dB, –1 dB of the reference level recorded in step 1. 3. Set the audio analyzer’s frequency to 10 kHz. Verify that the receiver’s unbalanced audio output is –7.5 dB to –10.5 dB of the reference level recorded in step 1. 4. Model T4V only: Place a 150 Ω load across the receiver’s balanced output, then connect this output to the audio analyzer. Verify that the output is 65 mVrms, "15 mV. Remove the 150 Ω load. 5. If you are finished testing the receiver, remove the test cable and reinstall the antenna (see “Reassembly,” page 8). Units that Pass If the receiver passes these tests, then it is functioning as expected and shouldn’t require alignment. If you did not use the customer’s microphone transmitter for these tests, check it for proper operation. If it also checks out of it it was not sent in with the receiver, inform the customer that the product has retested within specifications. Preliminary Tests 6 25C1020 (EA) Shure T4 Diversity Receiver Disassembly and Assembly To access the printed circuit (pc) board, disassemble the receiver. CAUTION Observe precautions when handling this static-sensitive device. Disassembly 1. Disconnect all power to the receiver. 2. Collapse the antennas and rotate them until they lie flat against the case. Place the receiver upside down. Remove and set aside the four screws securing the bottom of the case (Figure 2). Case mounting screws Case mounting screws Volume knob Antenna mounting screw Antenna mounting screw Figure 2. Bottom View of Case 3. Place the receiver in its normal operating position and rotate the antennas to their vertical positions. Note that an adhesive-backed nameplate at the at the rear of the unit holds the upper and bottom parts of the case together. To open the case, carefully separate the upper part from the bottom part at the front of the unit. Carefully swing the bottom part of the case away until the two halves are at a 90° angle, to allow removal of the circuit board and antennas (Figure 3). 4. After the circuit board has been removed, pull off and retain the Volume knob. 25C1020 (EA) 7 Disassembly and Assembly Shure T4 Diversity Receiver Antenna Case top Circuit board É É Case bottom Volume knob Mounting screw Figure 3. Reassembly 1. Slide the Volume knob back on: note how it is keyed to the flat part of the shaft. 2. Rotate the antennas to their vertical positions. Place the pc board, component-side up, inside the top half of the case: after feeding the antennas through their holes, make sure the notches in the case align with the Volume knob, the LEDs align with the holes in the upper half of the case, and that the board is fully seated on the studs. 3. Swing the two halves of the case together until they snap in place. 4. Rotate the antennas until they lie flat against the case. Turn the receiver upside down and secure the assembly with the four screws removed earlier (Figure 2, page 7). Check that the Volume knob rotates freely. Antenna Replacement The antennas can be replaced without disassembling the case. Rotate the antenna you are replacing to its vertical position, collapse it, and remove the mounting screw through its access hole in the bottom of the case (Figure 2). Insert the new antenna and start the screw from the bottom, leaving it loose enough for you to rotate the entire antenna between your fingers. Rotate the antenna in this way as you lightly press it into the case until you feel the base seat in the slot of the bracket on the pc board. Tighten the screw. Disassembly and Assembly 8 25C1020 (EA) Shure T4 Diversity Receiver Service Procedures Reference Material The Shure Wireless System T Series User’s Guide provides a description of the unit as well as operating instructions, troubleshooting suggestions, and technical data. Special Equipment and Tools In addition to the standard items described in the Service Equipment manual, you will need: S a wireless microphone with the same frequency (usually a T1, T2, or T11) to verify that the receiver is working properly S an audio amplifier with a high-impedance input (w10 kΩ) and a monitor speaker, for listening tests System Operating Frequencies Each receiver’s circuit board has a resistor next to the group letter (A–H, J–L) that identifies the range of frequencies on which the receiver can operate (see Figure 4). Table 1 shows the Group Letter and its associated frequencies. Note that this chart applies only to T4 receivers. Table 1 Pc Board Groups Group Frequency Range A 169.000–173.975 MHz B 174.000–179.975 MHz C 180.000–185.975 MHz D 186.000–191.975 MHz E 192.000–197.975 MHz F 198.000–203.975 MHz G 204.000–209.975 MHz H 210.000–215.975 MHz J 216.000–222.975 MHz K 223.000–229.975 MHz L 230.000–237.975 MHz Tables 2 and 3 provide information for identifying the system frequency. The Crystal Code, together with the appropriate Shure model number, identifies a specific operating frequency for transmitters and receivers. Note that, although a Crystal Code always designates a specific frequency, it may be used with different Group Letters on other products. 25C1020 (EA) 9 Service Procedures Shure T4 Diversity Receiver Table 2 FCC-Approved Operating Frequencies Group A Crystal Code Freq. (MHz) V 169.445 A W 171.845 B CA 176.200 B CC 177.600 C CE 182.200 C CF 183.600 D CG 186.200 E CL 192.200 F CQ 202.200 G CV 208.200 Table 3 ETSI-Approved Operating Frequencies Group Service Procedures Crystal Code Freq. (MHz) A B B B B B B B B C C C C C D D E F F F F G J AQ AY AZ ZZ BA NB BB ND NE NH NK NL CS S NP NR NX NY NZ PU PB PD PP 173.800 174.100 174.500 174.500 174.800 175.000 175.000 176.600 177.600 182.000 183.600 184.600 184.800 184.800 189.000 190.600 197.600 198.600 200.350 201.650 203.000 204.600 217.000 J PR 218.600 J PS 219.600 L PV 232.825 L PX 233.125 L PY 234.625 L PZ 237.325 10 25C1020 (EA) Shure T4 Diversity Receiver Changing the Frequency The operating frequency of the T4 Receiver may be changed within a specific group by changing the crystal on the pc board (for group information, see the preceding section). Check the receiver for proper operation before attempting to change its operating frequency. After installing the new crystal, perform the alignment procedures. Then run an operational test to ensure the receiver is functioning properly. Finally, update the label to show the new frequency and letter identification code. Note: To ensure proper operation, obtain the crystal from Shure and verify that it operates within the frequency range of the pc board. Since crystals are marked with the nominal oscillating frequency, not with a letter code, you can use the following equation to determine the frequency at which a receiver will operate with a given crystal: Carrier Frequency = (3 nominal crystal freq. in MHz) + 10.71 Alignment The alignment steps must be done together, as a single, continuous procedure. Before beginning, be sure to do the setup described in the following subsection, “Test Conditions.” Test Conditions The following are the standard test conditions for the T4 Receiver: S With a #1 Phillips screwdriver, remove the antennas. S Load the the unbalanced, audio output (J101) with a 3.3 kΩ resistor. S For RF adjustments, connect a 33 kΩ resistor between ground and the following points: Channel A: TPA4 (pin 13 of U1) Channel B: TPB4 (pin 13 of U2) S Set the potentiometers as follows: Volume (R126): Fully CW Squelch (R112): Midrange Audio level (R106 and R168): Midrange Mute level (R16 and R41): Midrange Test Cable 1. Obtain a 50 Ω coaxial cable for connecting the circuit boards to various test equipment. (To construct this cable, see “50 Ω Test Cable Assembly” in the Service Equipment manual.) Refer to Figure 4 for the locations of the test points, controls, and tuning components. 2. Tack-solder the cable to the pc board as follows: Channel A: Center conductor to the antenna input (TPA1) and shield to ground (TPA2) Channel B: Center conductor to the antenna input (TPB1) and shield to ground (TPB2) 25C1020 (EA) 11 Service Procedures Shure T4 Diversity Receiver Presettings Most field units should already be tuned closer to the desired settings than these approximations. However, you may need to preset units when you are changing the frequency or an RF coil, or when an unskilled person has attempted to retune them. Minimum inductance occurs when the core is level with the top of the can. Turning the core further counterclockwise or even removing it will not appreciably affect the inductance. Maximum inductance occurs when the core is about two turns less than its full clockwise rotation—about 3.2 mm (1/8 in.) below the top of the can. Never screw the core against the board. The manufacturer’s setting of the two smaller, IF coils (L2 and L11) is close to their ideal setting, so you generally would not preset them. For coils L3–L8 and L12–L15, refer to Table 2 or 3 (page 10) to determine where the desired frequency lies within the board’s group. For frequencies near the bottom of a group, use the maximum-inductance settings; for frequencies near the top of the group, use the minimum-inductance settings. Display Check 1. Connect an external 12–15 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 the 50 Ω cable you soldered to the pcb (antenna and ground). Set the generator’s controls as follows: S –20 dBm on the receiver’s operating frequency S "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. Service Procedures 12 25C1020 (EA) Shure T4 Diversity Receiver Antenna B TPB2 TPB1 Group designator (see Table 1) U101 D108 C150 XLR audio output connector (J102) D109 C145 Note: Used only on Presenter and Vocal Artist models R168 B U108 L108 Phone jack !/4-in. (J101) R41 L12 B B C118 C48 Edge of case bottom L13 B Volume control TPB4 Power input (J103) L14 U2 Note: Use Shure PS20 or PS20E R126 Knob B Channel B L15 B L11 U109 TPB3 B TP9 L7 Crystal (see Tables 2 and 3) B U102 “Audio Peak” (red) Y100 U3 L8 B “Diversity” (RF) (yellow) A (On earlier L2 U107 units only.) A Squelch control (R112) TPB7 TPA7 A L6 Channel A A U1 U103 “Power” (green) L5 TPA4 TPB5 A U104 U106 TPB6 L107 L4 A R16 A TP8 Note: L107 and L108 are not found on earlier units. TPA3 C6 TPA5 L3 A TPA6 R106 U105 A Antenna A TPA2 TPA1 Figure 4. Major Components 25C1020 (EA) 13 Service Procedures Shure T4 Diversity Receiver Coil Adjustments Each channel has to be adjusted separately. A: Channel A RF and IF 1. Disconnect the power to the receiver. Mute Channel B by grounding TPB7 (pin 14 of U106). Reconnect the power. 2. Adjust the signal generator’s 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 until 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 voltage at TPA4. Use a hex tuning wrench for all adjustments except L2, which requires a non-metallic screwdriver (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 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 detector 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 TPA5 (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 off the modulation of the signal generator. Set its output to the minimum 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 TPB7 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). Service Procedures 14 25C1020 (EA) Shure T4 Diversity Receiver 2. Connect power to the receiver. 3. Adjust 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 position 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 voltage 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 observe. 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, 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” 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 minimum position, then gradually increase the 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 “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. 25C1020 (EA) 15 Service Procedures Shure T4 Diversity Receiver Bench Checks Note: In this section, test points for Channel A are given first, and the corresponding test points for Channel B are enclosed in square brackets. DC Power n Check for 9 Vdc (±0.35 Vdc) at TP9 (pin 3 of U101): S 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 stage that is drawing excessive current. S If the voltage is zero: Check for solder bridges or shorted foil traces (defective pcb). S If the voltage is higher than normal or the other tests prove negative: Replace U101. n Check for 5 Vdc (±0.25 Vdc) at TP8 (pin 10 of U3). Tuning n First check that that the RF signal is being applied to the correct diversity channel and that the other channel is being muted with the jumper. n 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 obtain a reading of 1–2 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: S With the RF generator turned off, use a spectrum analyzer to measure the injection level at TPA3 [TPB3] for approximately –15 to –20 dBm. S 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 frequency of the receiver. Example: To receive 169.445 MHz, the local oscillator frequency should be 158.745 MHz (±.015 MHz). Crystal Y100 operates at a third of this frequency, or 52.915 MHz. The nominal crystal frequency, 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. n If any of the RF coils will not tune properly, check for frequency-dependent capacitors that are missing or have the wrong value. If the IF coil will not tune, check C9 [C52]. n 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 n With TPA7 [TPB7] connected to ground, the selected diversity channel should be squelched and the “A” [“B”] LED should be off, whether or not an RF input Bench Checks 16 25C1020 (EA) Shure T4 Diversity Receiver signal is present. If you obtain different results, compare the dc voltages at U106, U107 (earlier units only), U103, and U105 [U108] with those of a properly working unit, or replace the pc board. n If the muting circuit works but has insufficient adjustment range, set the RF generator for a –95 dBm signal and check TPA4 [TPB4] for 1–2 Vdc, as described in the preceding, “Tuning,” subsection. If you get a lower reading, consider the following: S Low RF levels at the input of U1 [U2] will cause inadequate noise at the output of U105D [U108A]. S 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). S If necessary, 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 n If there is no audio at the output of the receiver: S To verify that the receiver is not squelched, defeat the squelch circuit by rotating R16 [R41] fully CCW. There should be 9 Vdc at TPA7 [TPB7], and the yellow “A” [“B”] “Diversity” LED should be on. S If the preceding test does not yield the proper results, check for a problem in the squelch circuitry (see the “Muting” subsection, immediately above). n Next, check pin 6 of U1 [U2] for an audio signal of approximately –15 dBV. If there is no detected audio: 25C1020 (EA) S Check C1 [C44] and the components connected to pins 7–10 of U1 [U2]. S On earlier units only: Make sure that FL1 [FL4] is an 86A8920 ceramic discriminator and not an 86A8910 ceramic filter, which is similar in appearance. S Check the dc voltages at U1 [U2] against those of a known working unit. If no other problem is found, replace the IC. S 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 TPA5 [TPB5], use a 1 kΩ resistor in series at the test point to prevent loading the amplifier. S Check the Volume control (R126) and the components going to the audio output jack (J101). S On vocal models, check for a signal at the Low Z microphone-level output, J102. If no signal is present, check U109B, U109C, and associated components. S 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. 17 Bench Checks Shure T4 Diversity Receiver n If you cannot set the audio level properly with R106 [R168], make sure that the other diversity channel is squelched: only one channel should be activated during this adjustment. n 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 activated, check U103. n 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 specifications, repeak the quadrature coil, L107 [L108], for maximum ac output at TP5 [TP8] (see step 1 of “Channel A Audio,” page 14 [step 1 of “Channel B Audio,” page 15]). On earlier units only, which do not have L107, replace ceramic discriminator FL1 [FL4]. n If the audio circuitry works properly but the red audio 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. Bench Checks 18 25C1020 (EA) Shure T4 Diversity Receiver Notes: 25C1020 (EA) 19 Notes: Shure T4 Diversity Receiver 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 on 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 part for U105, U108, and U109 (manufactured by Raytheon) 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-dependent, and changed Q3 and Q8 from bipolar mixers to GaAs MESFET (gallium arsenide metal semiconductor field-effect 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. Should you replace the Harris detector with the Sanyo unit, be sure to remove those two resistors. Frequencies: The “G” version of the pc board introduced many new European frequencies, five additional board groups (E–J), and a consequent reassignment of some frequencies to different board groups. The revised board received 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 and FL4 with quadrature coils L107 and L108. Test Points: On earlier versions of the pc boards, the test points were designated as “TP1A,” “TP1B,” etc.; on newer boards, the designations are “TPA1,” TPB1,” etc. “J” Frequency Code: Starting in the summer of 1997, T Series transmitters and receivers tuned to 175.000 MHz have been labeled as “BB” rather than “J.” The change was made to avoid confusion with the different meaning of the “J” designation in the LX88 and ELX88 units. It is only a labeling change; the units are physically the same. “L” Frequencies: The “F” pcb assembly mainly addresses the addition of a new “L” group with new European frequencies. There were also a number of minor changes to capacitors, partly small corrections, mainly adaptations to simplify parts procurement and stocking. Replacement Parts and Drawings 20 25C1020 (EA) Shure T4 Diversity Receiver Parts Designations The following comments apply to the parts list and the schematic: Resistors: All resistors are surface-mount with 1/10 W rating and 1% tolerance. Capacitors: Unless otherwise noted, non-polarized capacitors are surfacemount NPO dielectric types with a 100 V capacity and a 5% tolerance, and polarized capacitors are tantalum types. Table 1 T4 Hardware Replacement Parts Reference Designation Description Shure Part No. A1 Printed Circuit Board Assembly 90_8550F [In the underlined space, insert the proper Group Code-Letter from Table 2 or 3, page 10.] E1 Antenna 95A8320 K1 Case Screws, Antenna Mounts & Antenna Screw Kit RPW612 Case Screw 30C1245A Antenna Mount Bracket 53A8322 Antenna Screw 30C1208A Hardware Kit 90VY1371 MP1 Case (top) 65B8198 MP2 Case (bottom) 65A8199 MP3 Knob (for Volume control) 65B8235 MP4 Screw, Hi–Lo, Pan (for case) 30C1245A MP5 Nameplate, Polycarbonate, Rear (Euro) 39A8368 MP6 Nameplate, Polycarbonate, Rear (Domestic) 39B8368 Table 2 T4 PCB Replacement Parts Reference Designation Description Shure Part No. C6, 48 Capacitor, Electrolytic, 470uF, 16V, 20% 86S629 C105,114,144, Capacitor, Electrolytic, SMD, 10uF, 35V, 149,151,153 20% 151BF106MC C111,116,127, Capacitor, Electrolytic, SMD, 1.0uF, 50V, 132,140,141, 10% 156 151BG105KB C118,145,150 Capacitor, Electrolytic, 47uF, 63V, 20% 86BE629 C129 Capacitor, Electrolytic, SMD, 4.7uF, 35V, 20% 151BF475MB C152 Capacitor, Electrolytic, SMD, 100uF, 16V, 20% 151BD107MD 25C1020 (EA) 21 Replacement Parts and Drawings Shure T4 Diversity Receiver D101,107,110, Diode, Signal, Switching, SOT–23, 100VDC 111,112,113 (MMBD7000L) 184A08 D108, 109 Rectifier, Silicon, 140VDC 184A20 FL2, 3, 5, 6 86A8910 Ceramic Filter, 10.7MHz J101 Phone Jack, Stereo, Right Angle, 1/4-inch 95A8329 J102 XLR connector (Vocal units only) 95A8400 J103 DC Power Jack 95A8328 L1,10,101,102 Ferrite Bead, SMD 805, 600 OHM ,103,104,105, 106 L2, L11 If Coil, 4.7uH 162A12 82A8005 L7, 8 Tunable, 10 mm, RF Coil, Red, 45nH L9 Inductor, SMD 1008, .22uH (220nH) L107, 108 Quadrature Coil, 10.7MHz 82A8003 162C06 82A8004 Q1, 6 MOSFET (metal-oxide-semiconductor fieldeffect transistor) SOT–143, (3SK131) Q2, 4, 5, 7 Transistor, UHF/VHF, RF, SOT–23, NPN, (MMBTH10L) Q3, 8 Amplifier, 2 Gate, Hi Gain, Lo Noise, SOT143 (3SK177) R16, 41, 106, Potentiometer, Linear Taper 5 kΩ 168 183A23 183A03 183A12 46C84 R112 Potentiometer, Linear Taper, 100 kΩ (Squelch) 46A8008 R126 Potentiometer, Log Taper, 10 kΩ (Volume) 46A8046 U1, U2 Integrated Circuit, FM IF, SO–16 (LA1235) 86A8877 U3 Compandor, SOL–16 (SA571D) U101 9 V Regulator (MC7809CT) 188A01 86A8944 U102, 106 Comparator, Quad, Low Power, SO–14 (LP339M) 188A123 U103 Switch, Multiplexer, Quad, SO–14 (HEF14066) 188A19 U104 LED Bar, Green/Yellow/Yellow/Red 95A8519 U105,108,109 Quad Op Amp, SO–14 (MC33179D) Y100 Crystal 188A49 40_8003A [In the underlined space, insert the appropriate Crystal Code from Tables 2 and 3, p. 10] Note: The tables on the following pages list frequency-dependent parts. Replacement Parts and Drawings 22 25C1020 (EA) Shure T4 Diversity Receiver In the following four-part table, “Grp” is the board’s frequency group, and “Desig” is the number of the resistor that designates the Group Number. The parts are listed across the tables in alphanumeric order. All capacitor tolerances are in picofarads. Table 3 Frequency-Dependent Parts I C8, C51 C10 C11 C12, C56 C17 C18 A R210 Not used 1 pF (0.1) 12 pF 18 pF 15 pF Not used Grp Desig B R211 1 pF (0.1 ) Not used 12 pF 15 pF 12 pF 1.8 pF (0.1) C R212 Not used 1 pF (0.1) 10 pF 15 pF 12 pF 1 pF (0.1) D R213 1.8 pF (0.1) NA 10 pF 12 pF 12 pF Not used E R214 1 pF (0.1) 1 pF (0.1) 20 pF 12 pF 10 pF 1 pF (0.1) F R215 Not used Not used 20 pF 12 pF 10 pF Not used G R216 Not used Not used 18 pF 10 pF 10 pF Not used H R217 1 pF (0.1) 1.8 pF (0.1) 15 pF 8.2 pF 8.2 p F 1 pF (0.1) J R218 1 pF (0.1) 1.8 pF (0.1) 15 pF 18 pF 15 pF 1.8 pF (0.1) K R219 Not used 1 pF (0.1) 15 pF 18 pF 15 pF 1.8 pF (0.1) L R220 1 pF (0.1) 1.8 pF (0.1) 12 pF 15 pF 15 pF Not used Frequency-Dependent Parts II Grp C19, C63 C20 C21 C33, C36 C40 C42 C54 A 56 pF 12 pF NA 15 pF 20 pF 20 pF 1 pF (0.1) B 56 pF 10 pF 1 pF (0.1) 15 pF 20 pF 20 pF NA C 56 pF 10 pF NA 12 pF 20 pF 20 pF 1 pF (0.1) D 56 pF 8.2 pF (0.25) 1 pF (0.1) 12 pF 20 pF 20 pF NA E 56 pF 8.2 pF (0.25) 1 pF (0.1) 10 pF 20 pF 20 pF 1 pF (0.1) F 56 pF 8.2 pF (0.25) NA 10 pF 20 pF 20 pF NA G 47 pF 6.8 pF (0.25) NA 8.2 pF (0.25) 20 pF 20 pF NA H 47 pF 5.6 pF (0.25) 1 pF (0.1) 10 pF 20 pF 20 pF NA J 56 pF 15 pF 1 pF (0.1) 6.8 pF (0.25) 10 pF 10 pF NA K 56 pF 15 pF NA 6.8 pF (0.25) 10 pF 10 pF 1 pF (0.1) L 56 pF 12 pF 1.8 pF (0.1) 5.6 pF (0.25) 10 pF 27 pF 1 pF (0.1) 25C1020 (EA) 23 Replacement Parts and Drawings Shure T4 Diversity Receiver Frequency-Dependent Parts III Grp C55 C60 C64 C61 C65 C77, C78 A 12 pF 15 pF 1 pF (0.1) 12 pF Not used 3.3 pF (0.1) B 12 pF 15 pF Not used 10 pF 1 pF (0.1) 3.3 pF (0.1) C 10 pF 12 pF 1.8 pF (0.1) 10 pF NA 1.8 pF (0.1) D 10 pF 12 pF 1 pF (0.1) 8.2 pF (0.25) 1 pF (0.1) 1.8 pF (0.1) E 20 pF 12 pF Not used 8.2 pF (0.25) 1 pF (0.1) 1 pF (0.1) F 20 pF 10 pF 1 pF (0.1) 8.2 pF (0.25) Not used 1 pF (0.1) G 20 pF 10 pF NA 6.8 pF (0.25) Not used 1 pF (0.1) H 18 pF 8.2 pF (0.25) 1 pF (0.1) 6.8 pF (0.25) Not used 1 pF (0.1) J 18 pF 18 pF Not used 15 pF 1.8 pF (0.1) 3.3 pF (0.1) K 15 pF 15 pF 1.8 pF (0.1) 15 pF 1 pF (0.1) 3.3 pF (0.1) L 12 pF 15 pF Not used 12 pF 1.8 pF (0.1) 3.3 pF (0.1) Frequency-Dependent Parts IV L3, L4, L6, L12, L13, L15 R24 R26 A 82A8003 82A8003 1.82 kΩ 24.9 kΩ Grp L5, L14 B 82A8003 82A8003 1.82 kΩ 24.9 kΩ C 82A8003 82A8003 1.82 kΩ 24.9 kΩ D 82A8003 82A8003 1.82 kΩ 24.9 kΩ E 82C8003 82A8003 1.82 kΩ 24.9 kΩ F 82C8003 82A8003 1.82 kΩ 24.9 kΩ G 82C8003 82A8003 1.82 kΩ 24.9 kΩ H 82C8003 82A8003 1.82 kΩ 24.9 kΩ J 82C8003 82C8003 1 kΩ 12.1 kΩ K 82C8003 82C8003 1 kΩ 12.1 kΩ L 82C8003 82C8003 1 kΩ 12.1 kΩ Replacement Parts and Drawings 24 25C1020 (EA) 1 TPB5 TPB2 TPB1 1 TPB4 1 1 TPB3 TP9 1 1 TPA3 TPB7 1 TPA7 TPA4 1 TPB6 TPA5 TP8 TPA6 1 TPA1 TPA2 Shure T4 Diversity Receiver Figure 5. T4 Receiver Pc Board, Component Side 25C1020 (EA) 25 Replacement Parts and Drawings Replacement Parts and Drawings 26 TP1A TP2A TP7A (U106, Pin 13) If 9 Vdc, Channel is ”ON” TP5A TP4A TP5B TP7A TP3A TP9 TP3B TP4B TP1B TP6B (Positive end of C40) 1 Vdc TP7B (U106, Pin 14) if 9 Vdc, Channel is ”ON” TP6A (Positive end of C111) 1 Vdc TP2B TP5B (U108, Pin 7) Audio TP5A (U105, Pin 8) Audio TP7B TP4B (U2, Pin 13) RF Alignment TP6B TP3B RF Test Point TP4A (U1, Pin 13) RF Alignment TP9 (U101, Pin 3) 9 Vdc TP2B 50 Ω Input Cable TP3A RF Test Point TP8 TP6A TP1B 50 Ω Input Cable Channel B TP2A 50 Ω Input Cable TP8 (U3, Pin) 5 Vdc TP – Test Points TP1A 50 Ω Input Cable Channel A Shure T4 Diversity Receiver Figure 6. Earlier Version of T4 Receiver Pc Board, Side 1 25C1020 (EA) N27 Channel A C4 .001 A101 TPA1 C8 N12 N24 N19 * C13 C12 C77 N87 1 53A8322 18 pF* 1 pF 3.3 pF* C19 1 L3 L4 1 56 pF* 3 3 4 4 TPA2 82A8003 R1 49.9k R6 49.9k 9V N4 N7 R7 33.2 N6 C7 0.5 pF N10 Q1 2 N15 C9 N16 DOT Q3 N14 R9 C14 N21 3 2 D 1 3 D N11 G2 3 1 82A8003* 4 C10 33.2 C11 47 pF N20 G1 3 1.8 pF* 12 pF* 3 N23 3 G1 183A12 2 150 pF 4 1 4 C15 3SK131/V12 4 1 S 4 R22 S N29 C17 C18 L2 6 R14 270 pF 183A23 L5 L6 1 15 pF* * TPA3 N26 20k C26 C165 7 9V 100 N27 1 8 R19 C22 9V C20 C21 R17 C24 .047 150 pF * 100 .001 100 N31 R20 12 pF* R15 .001 20k 100 C29 N202 .047 9V R5 1.82k N13 86A8910 FL3 Ceramic Filter C2 .047 N5 L1 162A12 R3 392 DOT 3 13 1 Q2 FL2 183A03 2 86A8910 2 N22 R11 Ceramic 825 R13 Filter 10 N30 R18 C25 499 .047 C3 .047 N17 1 2 4 L107 82A8004 3 1 6 N9 N2 11 8 R4 10k 9 10 N3 R8 4.99k 3 + C6 470 µF 16 V C5 .047 15 N18 U1 86A8877 C16 N25 7 LA1235 .01 R16 FM Detector N28 C30 14 5k 150 pF 2 5 13 6 N32 12 N33 16 4 TPA4 R174** C28 N36 4.99k .047 C27 .047 C31 Audio .001 R12 332 C23 .047 N8 8 CW Muting N34 L8 C76 C75 .001 82A8003 R24 N39 .001 N38 R23 4 C33 3 1.82k C32 1.82k C36 15 pF* 1 10 pF R172 15 pF* C37 R52 N86 49.9k N42 .001 R25 3 N40 R51 N43 N41499 49.9k N89 499 N85 C39 1 3 Q4 R173 Crystal 10 pF N44 1 Q5 183A03 Quad Coil 183A03 2 24.9k N46 L108 C40 2 N45 82A8004 R27 R26 Y100 20 pF C41 R28 2 24.9k 1.82k 4 C43 xxMHz 40-8003 33 pF 499 L10 N51 C42 N47 .001 N75 9V 3 1 6 C164 162A12 47 pF* L9 N50 I210 N210 R210 N212 R31 33 pF C45 R30 C46 Channel B A I212 220 nH N52 49.9k .047 .047 10k + C48 10k I211 N211 R211 N213 C47 R32 R44 R33 B I213 R34 .047 R35 11 392 9 8 10 C49 470 µF 4.99k 10k N203 1.82k N55 20k 1 N54 DOT R212 49.9k N53 N57 R36 .001 16V C50 U2 33.2 N56 C N59 TPB3 15 N58 N60 1 3 3 A102 TPB1 C51 N61 C52 R38 N64 N65 10k DOT 1 N62 2D R39 Q7 2 N63 L14 0.5 pF L15 N73 FL5 86A8877 R213 C53 N66 1 3 C58 7 * G2 1 4 D G2 332 C55 183A03 2 Ceramic D C57 C78 LA1235 Q6 C54 3 C56 Q8 33.2 1 47 pF CW 10k 12pF* 3 3 1 N67 N88 N68 2 N70 G1 3 FL6 R40 3 N71 .01 4 2 150 pF 1.8pF* Filter FM Detector R41 N72 C73 N75 4 3SK131/V12 4 1 S 825 R42 C59 G1 4 1 S 183A12 L11 6 Ceramic 53A8322 18 pF* 1 pF 3.3 pF* 1 C60 C61 I214 N214 R214 N216 Muting 86A8910 5k 150 pF 270pF 183A23 R43 82A8003* 82A8003 I216 E R50 2 4 5 13 L12 L13 6 16 C62 12 N76 10 Filter 4 10k 15 pF* * 1 N74 C63 N79 N77 .047 N69 20k I215 N215 R215 N217 TPB4 86A8910 C71 C166 7 8 9V 100 C64 C65 3 56 pF* 3 3 F I217 R45 R175** N80 C66 R46 C68 4 12 p* 1 N78 N83 R47 .047 150 pF N82 C69 TPB2 * C70 4.99k 100 499 .001 R21610k C67 9V .047 .001 100 .047 G R49 .047 10k 82A8003 C72 14 100 R217 C74 .047 H 5V .001 Audio 10k 9V 188A49 5 Pin 6 of U1 I218 N218 R218 U103A 1 7 14 10 J U105B N36 10k 13 12 R219 C102 U103D N220 2 K 6 11 188A19 I219 N219 10k N101 5V .33 188A19 TPA 5 7 188A49 R101 10 N90 R220 L I220 N102 8 N103 100k U105C 10k 9 8 9 C105 R103 R102 10 µF 6.81k U103C Pin 7 Channel A 35V N105 N104 40.2k 188A19 C104 + 6 9V (Pin 2 of R16) 120 pF D101 CW 9V R104 N34 R105 N106 N107 1 N108 200k B Channel Bias R107 5k 200k 20 mV ref. TPA6 C110 N110 R108 R106 1M 1 2 N113 150 pF N111 CW R112 C107 C108 R109 N117 N114 R110 N118 N115 1 2 R111 N116 N125 3 20k U105A 2 100k R114 5V 33 pF C111 + 10M 6 10M N171 499 N112 C109 184A08 C112 330 pF C113 100k N121 3 Mute Drive R115 49.9k 1.0 R117 188A49 3 150pF 1 .1 N123 5 188A49 R118 R113 50V 150pF R119 330pF U102A 100k 200k 1.5k C163 7 N128 R120 N126 +C114 N127 + C116 N125 20 mV ref. 4.75k N124 13 4 9V U109D 9V R121 7 188A04 1 10 µF, 35V 3 Volume C118 N132 R125 N133 J101 499 R122 10 10 C158 9V U105D 14 49.9k 50V R126 2 6 5V LP339MX 9V R123 R171 2.21k + C157 R128 188A49 C119 C120 .001 47 µF, 63V C121 3.32k 2 3 10k 12 11 .001 1 R127 6.81k N136 R129 CW .1 5 1 R130 .001 3 N135 100k N134 .0039 1M R131 R132 TPA7 9V N137 100k 100V N139 U106A 2 L101 9V N140 9V 16.5k 4 N138 24.9k R133 R134 162A12 R139 12 R136 N141 N131 1M * R137 D110 1k 188A04 * + 9V R138 1 49.9k LP339MX N201 9 1M C123 3 9V C124 N143 14 5V 11 2 3 Yellow * U102C U104B .001 13 8 184A08 9V 6 188A04 U106C 4 95A8519 N146 C126 10 5 16 7 13 2 LP339MX C161 8 * R141 1 N145 100k 188A04 188A04 9V C127 11 R142 U3 R143 R169 N147 .001 + 15 27.4k C128 LP339MX R145 U109A 1 R144 13 4 3 188A01 1k 12 1 µF, 7 0 N150 2 184A08 U102D .01 100k NE 571 D 2 N152 10k 3 10 188A49 N149 U102B 3 50V C129 N155 3 D111 14 N151 N153 Compandor TPB7 U106B 1 188A04 Pin 7 U2 Channel B + 7 C130 6 C131 2 10 LP339MX 12 1 4 11 R146 4.7 µF, 35V Red 188A04 5 .047 100 pF (pin 2 of R41) 49.9k 9 LP339MX N158 N157 C159 8 U104D 95A8519 N154 C125 9 R147 N80 .01 + N160 R148 N161 2 .01 C132 D107 14 N162 30.1k 200k C136 D112 1 R149 N166 8 U106D 1 9 150 pF 184A08 3 50V C134 188A04 5V TP8 N165 20k N167 C135 N168 TPB6 5V U108C 8 C137 LP339MX 33 pF 1 330 pF .01 C138 R151 R152 3 N170 N171 2 188A49 N164 6 C139 10 R155 + R154 330 pF Yellow 499 200k .1 N173 2 C140 5V N175 4.75k D113 U104C 95A8519 184A08 49.9k 1 1 Channel B N174 9V 5 1 U108A 50V N200 R156 3 C141 5V 12 188A49 5 C162 Pin 6 of U2 N83 188A49 U103B 2 R150 4 3 49.9k 1 + 13 4 .001 188A19 1k U108D 14 50V C144 N177 R157 N179 C145 N178 C143 184A08 14 N180 9V 13 .33 9V + R158 N119 U109C 4 3 5V 47 µF 10 µF 750 R159 L102 TPB 5 C160 L106 162A12 188A49 11 5 N93 R160 C146 12 100k 162A12 .001 63V N199 5V 35V N182 68.1 .001 188A49 100k N181 U108B 7 100V 2 3 J102 N176 11 D1 1 6 R162 C147 R161 Output 6.81k N183 .001 R163 68.1 R164 188A49 10 N184 Power 12-18Vdc D10 100V N185 40.2k C149 C150 R165 TP 9 N190 + N193 100k + C148 * Leave off R134, R136, C123. N189 U109B 8 C151 9V J103 D108 + R166 L103 750 N191 47 µF C156 10 µF, 35V 10 µF L104 + N188 I N187 O N186 2 9 On first production: 1 U101 1 N194 120 pF 10k 162A12 63V 35V 1 3 R167 D109 R170 2 50V R168 162A12 3 - 1 + C154 1k + UA7809C G N197 R17 = R45 = 49.9Ω CW 5k 10k N195 C152 C153 86A8944 .001 N198 3 1 Green R7 = R36 = 33.2Ω 100 µF N196 10 µF 16V L105 U104A 95A8519 35V C40 = 10 pF I92 C155 2 162A12 .001 **R174 and R175 are only used with the Harris FM Detector. I91 B Channel Bias 82A8003 4 L7 3 1 T4 Schematic (from 90-8550E-11) Channel A A101 TPA1 53A8322 C4 .001õF C8* C12* C77* C13 1 pF 1 3 4 * C19 TPA2 1 3 4 R6 49.9ĂkΩ C7 0.5 pF R7 33.2ĂΩ Q1 2 D G2 3 * C10 G1 3SK131/V12 4 1 S 183A23 * *C21 R17 C20 100ĂΩ * L3 * L4 *C11 9V R14 100ĂΩ C24 .001õF 4 3 1 3 4 * L5 C22 .001õF * L6 C9 R9 DOT 1 3 D 3 33.2 47 pF 3 183A12 2 150 pF G1 4 1 C15 4 R22 S L2 6 C18 270 pF * TPA3 20ĂkΩ .047õF C165 1 7 8 R19 9V C26 150 pF 100ĂΩ R20 R15 20ĂkΩ 100ĂΩ C29 .047õF 82A8003 4 L7 3 1 C76 .001õF R23 R24 1.82ĂkΩ 1.82ĂkΩ R172 C37 49.9ĂkΩ .001õF C33* R52 499ĂΩ 3 C39 10 pF Q4 183A03 2 R27 1.82ĂkΩ TPB1 A102 * C17 1 53A8322 C56* C63* TPB2 R35 49.9ĂkΩ C49 .001õF C57 *C78 1 pF 4 3 1 * L12 1 3 4 G2 G1 3 3SK131/V12 4 183A23 * *C65 R45 C64 100ĂΩ L13 * R36 33.2ĂΩ 2D Q6 *C54 1S C68 .001õF C75 .001õF R25 49.9ĂkΩ *C40 24.9ĂkΩ R26 Y100 xxMHz 40-8003 C55 * R43 9V 100ĂΩ 1 3 4 0.5 pF * L14 L15 * C102 0.33õF 5V 188A49 R101 10 8 100ĂkΩ U105C 9 R103 R102 6.81ĂkΩ 40.2ĂkΩ C104 C105 + 10 µF 120 pF 35V CW C60 * C43 .001õF L9 220 nH 4 L107 82A8004 1 6 R8 4.99ĂkΩ + C6 470 µF 16 V C5 .047õF 15 U1 86A8877 C16 7 LA1235 .01õF R16 FM Detector C30 14 5ĂkΩ 2 5 150 pF 13 6 12 16 4 TPA4 R174** C28 4.99ĂkΩ .047õF C27 .047õF Audio C31 .001õF 150 pF *C61 9V R44 20ĂkΩ 7 13 6 R34 1.82ĂkΩ DOT 1 3 DOT 1 Q7 1 3 183A03 2 2 FL6 R40 2 825ĂΩ C59 Ceramic R42 270ĂpF Filter 10ĂΩ 86A8910 R46 C69 499ĂΩ 9V .047õF R49 100ĂΩ 9V U103A 1 188A19 8 U103C 188A19 9V D101 R33 392ĂΩ C52 R38 2 D G2 47 pF 33.2ĂΩ Q8 3 1 4 G1 4 1 S 183A12 L11 6 R50 20ĂkΩ C71 C166 7 8 3 R47 .047õF 150 pF 100ĂΩ C72 .047õF 188A49 U105B TPA5 R18 499ĂΩ 1 3 CW Muting Quad Coil L108 82A8004 2 4 2 C58 5 2 2 3 C32 10 pF C66 .001õF Pin 6 of U1 R11 825ĂΩ 8 R4 10ĂkΩ 8 9 10 11 R51 499ĂΩ 3 Q5 183A03 R28 499ĂΩ C42* 1 86A8910 FL3 Ceramic Filter L8 82A8003 TPB3 4 3 R3 392ĂΩ 3 1 R5 1.82ĂkΩ 1 C50 5V Pin 7 Channel A (Pin 2 of R16) 4 3 1 * C36 R173 Crystal 24.9ĂkΩ C41 33 pF C164 33 pF R31 49.9ĂkΩ C51* 1 Q3 2 C14 9V Channel B L1 162A12 C2 C3 .047õF .047õF DOT 13 Q2 FL2 183A03 2 86A8910 Ceramic R12 332ĂΩ R13 Filter 10ĂΩ C23 C25 .047õF .047õF 9V R1 49.9ĂkΩ 12 2 14 10 7 11 9 6 C45 .047õF 3 L10 162A12 11 1 FL5 Ceramic Filter 86A8910 R39 332ĂΩ 3 C46 .047õF 3 24 C62 .047õF C70 .047õF 1 6 R30 10ĂkΩ 9 8 10 U2 86A8877 LA1235 FM Detector 5 12 13 6 16 TPB4 C67 14 .047õF + C48 470 µF 16V C47 R32 4.99ĂkΩ .047õF 15 7 C53 .01õF R41 C73 150 pF 5ĂkΩ R175** 4.99ĂkΩ C74 Audio .001õF CW Muting A B C D E F G H J U103D 188A19 K L I210 R210 I212 10ĂkΩ R211 I213 10ĂkΩ R212 10ĂkΩ R213 10ĂkΩ I214 R214 I216 10ĂkΩ I215 R215 I217 10ĂkΩ R216 10ĂkΩ R217 10ĂkΩ I218 R218 10ĂkΩ R219 N220 I219 10k R220 I220 10k I211 9V * R105 200ĂkΩ B Channel Bias R107 20 mV ref. 1ĂMΩ 1 2 CW R112 R109 C109 C107 C108 R110 1 2 R111 3 2 100ĂkΩ R114 5V U105A R113 33 pF C111 + 6 10M 330ĂpF 499ĂΩ 0.1õF 184A08 10ĂMΩ C112 3 330 pF Mute Drive 100ĂkΩ R115 1õF R117 188A49 3 C163 1 5 188A49 R118 150ĂpF 49.9ĂkΩ 50V R119 C113 U102A 100ĂkΩ 200ĂkΩ 1.5ĂkΩ 150ĂpF R120 7 + C116 +C114 13 4 20 mV ref. 4.75ĂkΩ 9V U109D 9V R121 7 188A04 1õF 10 µF, 35V 3 Volume 14 C118 499ĂΩ R125 R171 R122 10ĂΩ C158 J101 U105D 9V 49.9ĂkΩ 2.21ĂkΩ 50V R126 2 6 5V LP339MX 9V R123 10ĂΩ + C157 .0039õF R128 C119 10ĂkΩ 1 47 µF, 63V C121 3.32ĂkΩ 2 3 .001õF 100ĂkΩ 12 11 188A49 .001õF R127 CW 0.1õF R129 5 1 3 R130 .001õF 6.81ĂkΩ 1ĂMΩ R131 R132 C120 TPA7 9V 100ĂkΩ 100V U106A 2 L101 9V 9V 16.5ĂkΩ 4 R134 24.9k R133 162A12 R139 12 R136 N.S. 1ĂMΩ D110 1ĂkΩ 188A04 R137 N.S. R138 1 + 9V LP339MX 49.9Ăk 9 1ĂMΩ C123 3 9V C124 Ω 14 5V 11 2 3 Yellow N.S. U102C U104B .001õF 13 8 184A08 9V 6 C126 N.S. 188A04 U106C 4 95A8519 10 5 16 7 13 2 LP339MX C161 8 R141 1 188A04 188A04 9V C127 11 R142 U3 R143 R169 + 15 27.4ĂkΩ .001õF C128 LP339MX R145 U109A 1 R144 13 4 3 188A01 2 1ĂkΩ 12 1 µF, 7 184A08 100ĂkΩ U102D .01õF 0ĂΩ 100ĂkΩ NE 571 D 2 3 10 10Ăk 188A49 3 50V C129 D111 14 3 Compandor U102B TPB7 U106B 1 188A04 Pin 7 U2 Channel B ΩC130 + 7 6 C131 2 10 LP339MX 12 1 4 11 R146 4.7 µF, 35V Red 188A04 5 .047õF 100 pF (pin 2 of R41) 49.9ĂkΩ 9 LP 339 MX C159 8 U104D 95A8519 C125 9 R148 R147 + .01õF 2 C132 D107 .01õF 200ĂkΩ C136 30.1ĂkΩ U106D 14 D112 1õF R149 8 1 9 150 pF 184A08 3 50V C134 188A04 5V TP8 C135 TPB6 20ĂkΩ 5V U108C 8 C137 LP339MX 33 pF 1 330 pF C138 R151 .01õF R152 3 2 188A49 C139 10 6 49.9ĂkΩ + R154 330 pF Yellow 2 200ĂkΩ 499ĂΩ 0.1õF C140 5V 4.75ĂkΩ D113 U104C 95A8519 184A08 R155 1õF 1 Channel B 9V 5 1 U108A 50V C141 R156 3 5V 12 188A49 5 Pin 6 of U2 C162 .001õF 188A49 U103B 2 R150 49.9ĂkΩ 4 3 1õF + 13 4 188A19 1ĂkΩ U108D 14 50V C144 C145 C143 R157 184A08 9V 13 .33 9V U109C 14 + R158 4 3 5V 47 µF 10 µF 750ĂΩ R159 L102 C160 L106 162A12 11 5 188A49 TPB5 R160 63V C146 12 162A12 100ĂkΩ 5V 35V .001õF 7 .001õF 188A49 68.1ĂΩ 100ĂkΩ U108B 100V 2 3 J102 11 D1 1 6 C147 R162 R161 Output R163 .001õF 6.81ĂkΩ 68.1 R164 10 188A49 Power 12-18Vdc D10 100ĂV * FrequencyĆdependent parts: see TableĂ7 near the end of C149 40.2Ăk C150 R165 TP 9 + Ω C148 100ĂkΩ + U109B 8 C151 9V the manual. J103 D108 + R166 L103 750ĂΩ 47 µF C156 10 µF, 35V 10 µF L104 + I O 120 pF 2 9 U101 1õF 1 162A12 63V 10ĂkΩ **R174 and R175 are only used with the Harris FM Detector. 35V 1 R167 3 D109 R170 2 R168 162A12 50V 3 - 1 UA7809C G + C154 1k + CW 5ĂkΩ N.S. (not stuffed): Leave off R134, R136, C123, C126. 10ĂkΩ C152 C153 86A8944 .001õF 3 1 Green 100 µF 10 µF 16V L105 U104A On first production: 35V I92 C155 2 95A8519 162A12 R17 = R45 = 49.9ĂΩ .001õF R7 = R36 = 33.2ĂΩ I91 C110 150 pF R108 20ĂkΩ 200ĂkΩ R106 5ĂkΩ 1 TPA6 B Channel Bias R104 T4 Schematic C40 = 10 pF (from 90-8550F-11) Ceramic Discriminator 9V Antenna TP1A 1 A101 N24 C8 R6 24.9k 18pF* N19 C13 1pF C19 56pF* 4 3 1 L3 N87 C77 N20 N6 C20 12pF* D 2 C11 12pF* C7 100 C24 .001 N11 0.5pF N14 TP3A L6 4 N23 3 1 82A8003 3 4 82A8003 N27 C22 .001 R14 9V C21 * R17 100 N10 L5 1 499 G2 C10 3SK131/V12 G1 3 1.8pF* 1S 4 183A23 N26 3.3pF* L4 1 3 4 TP2A 82A8003 R7 N7 Q1 N12 C17 15pF* 183A03 Q3 C18 150pF * R15 7.5K L7 C39 1pF 4 3 1 C33 15pF* R52 N41 N43 1.0K Q4 183A03 3 N38 R23 C34 * N86 332 332 C35 * L2 R11 FL3 825 2 Ceramic Filter C15 270pF 64 1 R13 10 C26 N31 .047 C29 .047 C23 .047 3 C1 56pF 2 4 14 5 12 13 N32 TP4A C28 .047 C27 .047 9V R20 100 9 R26 Y100 12.1K xxMHz Crystal 40–8003 4 3 1 3 1 C30 .01 150pF N85 R28 499 N47 C43 .001 L9 220nH Ceramic Discriminator 1 N73 TP2B C51 * C56 18pF* C63 56pF* N59 N67 C57 C78 82A8003 C55 12pF* N75 R43 9V 100 N56 C50 N60 0.5pF L15 1 L14 4 3 3 N71 4 C60 1 82A8003 82A8003 15pF* C66 .001 TP3B C58 C61 * N69 N63 3 1 183A03 Q8 150pF R44 7.5K R38 N76 R47 499 R50 C52 N64 33.2 1 6 2 C71 .047 N65 47pF 4 L11 C59 270pF N62 86A8910 R40 2 FL6 825 Ceramic Filter DOT 1 3 78 3 N82 9V C72 .047 R49 100 N51 1 R42 10 R46 499 N54 DOT N55 3 1 3 86A8910 Q7 R39 FL5 183A03 332 2 2 Ceramic Filter N70 N72 C62 .047 N79 C69 .047 C44 56pF DOT 3 1 R29 287 86A8920 2 FL4 N50 R30 C46 .047 C45 .047 N57 499 Q6 2D G2 C54 N88 N68 3SK131/V12 G1 3 1.8pF* 4 1 3.3pF* 1pF 183A23 S N74 L12 L13 1 4 C64 C65 3 3 R45 C68 12pF* * 1 4 100 .001 82A8003 N61 162A03 R33 392 R34 1.82K R36 N49 L10 9V R35 N53 24.9k N34 Audio C32 1pF R31 49.9K C49 .001 Muting N33 N36 CW C31 .001 N75 Antenna A102 TP1B N25 R16 5K 6 16 N48 Channel B 26.7k C16 7 Q5 183A03 2 N45 C40 20pF C42 47pF* N18 15 + C6 470uF 16V R10 N40 N42 R51 1.0K N44 2 C5 .047 R8 2.21K 10 U1 86A8877 LA1235 FM Detector IC N28 N30 C25 .047 R18 499 1 332 N9 8 11 L8 82A8003 C36 15pF* R25 49.9K 1 C41 .001 47pF 3 N8 37.4K C75 N39 .001 N46 R27 1.0K N16 DOT 1 3 86A8910 Q2 FL2 183A03 N17 2 2 Ceramic Filter N22 R12 332 DOT 3 1 86A8920 2 FL1 N3 R2 287 R4 N5 3 78 R22 R24 C37 .001 R5 1.82K N13 DOT 1 3 86A8910 1 R19 499 9V 82A8003 N15 2 N29 82A8003 C76 .001 C9 33.2 3 N21 1 C14 R9 N2 162A03 C3 N4 C4 .001 * C12 R3 392 .047 R1 49.9K N1 C2 Channel A L1 .047 N27 N52 8 11 1 3 332 9 U2 86A8877 LA1235 FM Detector IC N77 C70 .047 2 4 14 5 R32 2.21K 10 12 13 6 16 TP4B N78 C74 C67 .001 .047 15 N58 C47 .047 R37 + C48 470uF 16V 26.7k C53 N66 7 C73 150pF .01 R41 5K CW Muting N80 N83 Audio 37.4K E 1999, Shure Brothers Inc. 27C1020 (SB) T4 Earlier Version Schematic (page 1 of 2) Pin 6 of U1 N36 N101 TP5A 188A120 10 RC4156M 8 U105 C 9 R103 R102 6.81K 22.1K N105 N104 C104 C105 + 220pF 10uF CW 35V N106 N34 C110 150pF R104 N107 N108 100K N111 R108 20k 5V U105 A 3 C107 1 188A120 330pF R119 4.75k RC4156M C113 330pF N124 C159 .001 6 3 U107 A 7 1 12 11 RC4156M 9V R135 100K 5V TP6A N113 3 2 184A08 R113 49.9K C109 R109 499 .1 4 9V C111 + 1.0 50V R121 49.9K 14 C157 .001 188A120 N114 N134 R107 1M R110 N117 10M R117 100K N125 R122 2.21K 9V 4 U107 B 2 188A04 5 C158 .001 5 N135 R140 100K 11 N144 C125 .01 14 12 N148 U103 D 7 C128 .01 R159 100K N181 188A120 TP5B 5 RC4156M U108 B 7 D107 1 C135 N167 188A120 330pF C139 R154 4156M 330pF 4.75k Channel B N174 (Pin 6 of U2) 5V N83 C143 .33 5V C134 LP339MX 10 7 LP339MX 33pF 2 N170 R152 C138 R151 200K .1 499 3 2 184A08 N173 1 U108 A 3 TP6B N168 N171 R155 49.9K RC4156M 4 188A120 188A04 9 LP339MX 14 U106 D N166 C137 .01 8 N125 8 LP339MX C163 14 U107 C 150pF 9 Move 150 pF close to pin 8 of NE571. N116 R114 N123 100K 5 C112 150pF + C116 1.O 50V 188A04 N201 3 Yellow N145 9V R145 100K 24.9k R139 1.0K 184A08 D101 1 3 2 5V U104 B R169 4 1 2 N154 2 D112 184A08 1 100K 184A08 3 D111 TP7B 188A120 2 3 188A04 U109 A 3 RC4156M C131 100pF N146 C126 16.5K R136 N141 * * 9V C123 + * C124 .001 C114 Volume N126 + N127 C118 10uF x 35V 3 10k 2 9V R126 C119 47uF x 63V 1 .1 R129 R130 CW 1M 100K R120 7 N128 188A120 6 R128 C120 6.81K .0039 N137 R132 R131 9V Mute Drive RC4156M U109 D N136 TP7A 1 6 20mV Ref. R123 R171 10 10 13 188A04 499 9V R134 R137 49.9K N143 N140 9V R133 1M 9 8 6 N164 1 6 U104C 95A8519 5 D101 1 N200 3 2 R150 1.0K 184A08 9V N175 R156 49.9K 9V N182 1 L101 162A03 9V C161 .001 N149 R144 4 10K C130 .047 3 U102 B R143 1.0K N153 2 7 Red U104 D 8 12 5 188A04 95A8519 R158 N119 100K 12 C162 .001 4 U109 C N177 C144 R157 N179 C145 N178 N180 + x 47uF x 63V L102 10uF 35V 750 162A03 R160 C146 68.1 .001 N176 100V 14 11 RC4156M C155 3 N139 9V D1 L105 162A03 N133 2 J101 9V 5V POWER 12–18VDC L103 162A03 J103 N186 + N187 2 3 – 1 162A03 C154 .001 N196 I91 3.32K R138 1M 188A04 5 C141 188A120 1.0 + 13 50V C160 .001 6 11 R162 6.81K N183 R163 N185 22.1K C151 + C148 10uF 35V 220pF N194 1 2 5K CW R168 3 R125 N131 14 U102 C LP339MX 8 16 7 13 N147 C127 11 15 R141 U3 2 + 12 27.4K 188A01 13 N150 0 1.0 x 50V N151 U102 D NE571D N152 14 Compandor IC + C129 N155 3 188A04 10 R146 4.7uF x 35V 4 11 9 10 LP339MX 1 N158 49.9K N157 R147 C132 + 1.0 30.1k 50V N162 TP8 5V * R142 N132 C121 .001 100V Yellow +C140 1.0 50V 4 188A19 5 3 U103 B 10 8 B Channel Bias 5V 3 U106 B N161 9V R127 100K 2 N138 U106 C 10 11 100K U108 C 9V LP339MX 2 188A19 R148 R118 1.5K 20mV Ref LP339MX Pin 7 U2 Channel B (Pin 2 of R41) N80 N160 C136 R149 150pF 9 N165 20k N171 10M 13 9V R105 200K 1 R112 100K 3 N110 CW 2 N121 U106 A 188A04 4 12 U103 A 9 B Channel bias R111 188A19 1 N142 188A04 12 LP339MX D101 N112 U105 D 5V 9V 9V 9V N118 33pF R115 200K 13 Note: Net name must be equal at each B Channel bias point. 1 5K R106 C108 N115 2 N103 6 Pin 7 Channel A (Pin 2 of R16) N102 188A19 8 100K U103 C C102 .33 R101 5V D10 R164 D108 9V D109 I O U101 3 1 G 86A8944 UA7809C N188 C153 + 10uF 35V I92 N184 10 TP9 + C152 100uF 16V R170 1.0K N198 1 Green 95A8519 2 U104 A *Leave off R134, R136, C123 First production assembled with R17=R45=49.9 ohms and R7=R36=33.2 ohms C40=10 pF 100K C156 1.0 50V + U109 B R166 10K 9 N197 R161 68.1 188A120 R167 8 C149 R165 + 10uF x 35V 750 N195 N193 L106 162A03 N199 2 3 1 C147 .001 100V C150 N189 47uF x 63V N190 J102 Output L104 162A03 N191 10K RC4156M .001 E 1999, Shure Brothers Inc. 27C1020 (SB) T4 Earlier Version Schematic (page 2 of 2)
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Key Features
- Single-channel, crystal-controlled
- 169 MHz to 238 MHz VHF-FM band
- Diversity reception
- Two independent RF sections
- Single-element, quarter-wave antennas
- Noise-operated squelch system
- Audio output
- Peak LED
Frequently Answers and Questions
What is the operating frequency range of the Shure T T4?
The Shure T T4 operates within the 169 MHz to 238 MHz VHF-FM band.
How many channels does the Shure T T4 have?
The Shure T T4 is a single-channel receiver.
What type of antennas does the Shure T T4 use?
The Shure T T4 uses two single-element, quarter-wave antennas for diversity reception.
What is the purpose of the noise-operated squelch system in the Shure T T4?
The noise-operated squelch system provides both diversity-channel selection and muting. It selects the channel with less noise and mutes the other channel during periods of low signal strength.
What is the function of the peak LED on the Shure T T4?
The red peak LED warns the user when the transmitter deviation is approaching the limit of 15 kHz.
How do I change the operating frequency of the Shure T T4?
The operating frequency of the T4 Receiver may be changed within a specific group by changing the crystal on the pc board. Check the receiver for proper operation before attempting to change its operating frequency.
What are the standard test conditions for the Shure T T4?
The standard test conditions for the Shure T T4 include loading the unbalanced audio output (J101) with a 3.3 kΩ resistor, connecting a 33 kΩ resistor between ground and specific test points for RF adjustments, and setting the potentiometers for volume, squelch and audio level to specific positions.