Shure Т1 User Manual

Shure Incorporated 222 Hartrey Avenue Evanston IL 60202-3696 U.S.A.

T Wireless System

SERVICE MANUAL CHANGE NOTICE

T1/TC1 WIRELESS BODY-PACK TRANSMITTER

Changes and corrections have been made to the Service Manual for the T1 Body-Pack Transmitter. To update your Service Manual, remove t he pages identified in the tables below a nd 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.

T1 BODY-PACK TRANSMITTER SERVICE MANUAL REVISION HISTORY

Release Part Number Date Code Color

Original 25A1016 QH White Revision 1 25B1016 SB Pink Revision 2 25C1016 SI White Revision 3 25C1016 TL White Revision 4 25C1016 AF White Revision 5 25C1016 BA White

Revision 6 25C1016 CC Red

CHANGES EFFECTIVE MARCH 17, 2003

REMOVE

these pages from the

T1 Service Manual

these new Revision pages into the

INSERT

T1 Service Manual

Page 22 Page 22

E1999, Shure Incorporated Printed in U.S.A. 25–1016–1 (CC)

T1/TC1 Body-Pack Transmitters

ББББББ

Characteristics

General

This section tells how to service and align the T1G, T1, TC1, and the discontinued T1P Body-Pack Transmitters (Figure 1). These single-channel, crystal-controlled units operate in the 169 Band.



25C1016 (CC)

MHz to 216 MHz VHF

Guitarist T1G

and TC1

mitter

Trans-

Figure 1.

1. Phone jack

2. Antenna

3. Tini “

4. Lavalier microphone

Presenter T1 Transmitter

Presenter T1P Transmitter

(discontinued model)

/4Ȃ (guitar or headset input)

Q-G” (Lavalier, headset, WA302 input)

Service Note: Shure recommends that all service procedures be

performed by a factory-authorized service center or returned directly

to Shure Brothers Inc.

E1999, Shure, Inc. Printed in U.S.A.

25C1016 (CC)

Licensing: Operation may require a user license. Frequency or

power-output modifications may violate this product’s approvals.

Contact your country’s communications authorities.

Characteristics

Shure T1 Body-Pack Transmitters

Circuit Description

The T1 transmitter contains one circuit board which comprises an audio and an RFsection. It is intended for use with the matching T3 and T4 receivers.

Audio Section

Input: Audio signals enter via a 1/4-in. phone jack, with the signal on the tip and the ground on the ring ( discontinued model

S Pin 1: Ground

S Pin 2: Supplies regulated 5 Vdc bias for electret condenser mi-

crophones

S Pin 3: Audio input

S Pin 4: 20 kΩ load resistor connected to pin 3 for Shure electret

microphones

Preamplifier Stage: This is centered in one section of the operational amplifier (U102C). An externally accessible potentiometer (R125) adjusts the voltage gain of this stage over a 40 dB range.

T1G), an attached microphone (the

T1P), or a four-pin, Tini Q-G



, connector (T1):

RF Section

Passive Pre-emphasis Network and Compandor: The network (R145, C110, C111, R112, and R115) has a pole at 63 microseconds and a zero at 1 microsecond. The (U101A) provides a 2:1 logarithmic compression of the audio signal.

Noise and Distortion: U102A lowers the noise floor, and an internal potentiometer (R130) nulls the system audio distortion. Operational amplifier U102B, operating as a two-pole, active, low-pass filter, restricts the bandwidth of the system to audio frequencies.

Limiting: signal leaving the audio section via U102B. Beginning in July 1995, this section was removed from the “A,” “B,” and “C” boards but left in a newly designated “T” board.

5 Vdc Bias and

channel (U101B) supplies regulated, low-noise 5 Vdc bias to various audio and protection” to the circuit. Q106 drives LED D101 (“Power On”), and Q107

LED D102 (“Low Battery”).

drives

Audio Input: Processed audio enters R217, an internal potentiometer that is adjusted for 15 kHz deviation (100% modulation) when the audio section provides a –2.2 dBV, 1 kHz tone.

PNP transistors Q103 and Q104 limit the level of the audio

LED Drive Circuits: The NE571D’s identical second

RF circuit points. Transistor Q105 provides “reverse battery

NE571D integrated circuit compandor

Oscillation: The audio then goes to varactor diode D201, which is part of the modulated oscillator-tripler stage (Q201). The latter’s baseemitter circuit operates as a crystal-controlled Colpitts oscillator in the

MHz region. Fundamental-mode crystal Y201 is tuned 10 kHz below

20 series resonance by the series combination of frequency-netting coil

2Characteristics

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Shure T1 Body-Pack Transmitters

L209, diode D201, capacitor C214, and capacitor divider C224 and C230.

Frequency and Temperature Stability: To ensure frequency stability despite changes in the battery voltage, regulated 5 Vdc bias is applied to the varactor diode and to the base of Q201. Temperature compensation is provided by C224, C230, and C214.

Tuned Circuits

Stage 1: The collector circuit of Q201 is tuned to the third harmonic

of the oscillator frequency (approximately 60 L202, C217, and C233. (The latter components also form a capacitivelytapped voltage divider for matching the signal to the base of Q203.) The output is double-tuned to provide high-spectral purity. Regulated dc bias is again employed to minimize changes in loading on the oscillator stage and to stabilize the drive levels.

Stage 2: Q203 operates as a frequency tripler, with its collector circuit tuned to the output frequency (for example, 180 L204, C215, C237, C236, L207, C235, and C222 perform tuning and impedance-matching functions. As in the preceding stage, regulated dc bias is applied to the base circuit to stabilize the drive level, and the output is double-tuned to provide spectral purity.

MHz) by L205, C225, C234,

MHz). In this case,

Stage 3: Q204 operates as a tuned amplifier. Resistive loading on the input provides stability. The output circuit consists of a resonant tank circuit (L203 and C213) capacitively coupled to a low-pass filter (C219, L206, and C218). C213 and C219 provide a capacitively tapped voltage divider for matching into the low-pass filter.

Transmitter Output

Transmitter: This can deliver up to +17 dBm (50 mW) to the an-

tenna. No user adjustment permits this value to be exceeded. The unit should be powered exclusively by a 9 Vdc dry battery (an alkaline type, such as a Duracell

Voltage Measurements: With 9 Vdc applied to the unit, the following voltages should appear at the terminals of the output transistor;

S Vc = 8.88 Vdc

S Vb = .450 Vdc

S Ve = .473 Vdc.

S Base current = .29 mAdc

S Emitter current = 21.5 mAdc

S Collector current = 21.8 mAdc

S Power input = 183 mW

The output power is +16.5 dBm (44.7 mW) into a 50 Ω load, at a frequency of 169.445 6 Vdc, the final collector current drops to 15 mAdc and the output power declines to +13.9 dBm (24.4 mW).

MN1604, is recommended).

MHz. At the minimum acceptable battery voltage of

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Characteristics

Shure T1 Body-Pack Transmitters

Antenna: This is a quarter-wavelength, permanently attached, flexible wire. The ground plane of the circuit serves as an untuned counterpoise capacitively coupled to the body of the user.

Spurious Emissions: To minimize the production and radiation of spurious emissions and harmonic energy, and to promote stable operation, the collector of each 9-volt supply by ferrite chokes, resistors, and bypass capacitors. The base circuits are similarly decoupled except that they use resistor-capac-

R-C) networks, whose higher-impedance levels are more appropri-

itor ( ate.

RF stage is separately decoupled from the

4Characteristics

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Preliminary Tests

Listening Tests

Before disassembling the unit, operate it to determine whether it is

functioning normally.

Focused Testing: First and most important: Review any customer complaint or request and focus your listening and functional tests on any reported problem. For example, for “short range” and “drop-outs” complaints, perform only the there is a strong indication that the customer is using the product incorrectly (e.g., not keeping the transmitter in the receiver’s line of sight, not avoiding metal enclosures or TV interference). Return the unit to the customer together with an explanation of the proper set-up procedures.

For complaints of distortion or other audio problems, try a “standard” lavalier or headset microphone (you should have one of each microphone on-hand for testing) and perform the audio tests in this section.

Functional Tests

Shure T1 Body-Pack Transmitters

RF tests in this section. If the unit passes these,

RF Tests

1. Remove the case top, mute the audio, and apply 9 Vdc to the battery terminals.

2. Measure the current drain: it should not exceed 35 mA.

3. Maximize the signal received on the spectrum analyzer by attaching a telescoping whip antenna to it. Then measure the near-field output power: it should be 7 dBm.

(If you are unsure of the results you obtain here, measure the output power conductively by soldering a 50 Ω cable to the out- put of the transmitter. Verify that the output power is 15 dBm, 2 dBm.)

4. Verify that the carrier frequency of the transmitter varies from its nominal value by no more than "6 kHz.

5. Check for an intermittent problem by shaking the transmitter and tapping on it. As you do so, try to keep it at a constant distance from the spectrum analyzer. Verify that the output power on the spectrum analyzer shows no large and sudden drops in power level (it will, however, vary a few dB with hand position).

6. Turn off the transmitter.

If the transmitter passes the above tests, its

working as designed.

RF circuits are

Audio Tests

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A: Verify the Matching Receiver

1. Connect the signal generator to the receiver through a 50 Ω cable. Tack-solder the center conductor to the antenna input and ground the shield of the cable to pcb ground.

Preliminary Tests

Shure T1 Body-Pack Transmitters

2. Set the

Amplitude: –20 dBm Modulation: 1 kHz Deviation: 15 kHz Frequency: T1 operating frequency

3. Connect the audio from the unbalanced output to the audio analyzer with a 3.3 kΩ load. Turn the Volume control all the way up.

4. For the associated T3 or T4, verify the following:

S audio level is 400 mVrms ("90 mV) S thd = <0.75%

RF generator as follows:

B: Check the Transmitter

1. Disconnect the signal generator from the receiver. Monitor the receiver’s unbalanced audio output with a 3.3 kΩ load and the audio analyzer. Check that the receiver’s Volume control is still at its maximum setting.

2. Unmute the transmitter and turn its gain to the minimum setting. Connect an input cable as follows:

T1 and T1G: Use adapter cables to input the audio to the bodypack input.

Units That Pass

good, then the system is functioning as expected and shouldn’t require tuning and alignment. Inform the customer that the product has retested within specifications.

T1P: Disassemble the case, remove the microphone, and attach the adapter cable to the four-pin header of the audio input.

3. Inject a 775 mV, 1 kHz signal from the audio analyzer into the adapter cable and verify the following:

S the amplitude from receiver’s unbalanced output equals

400 mVrms ("90 mV)

S thd = <0.75%

4. Change the frequency of the audio generator to 100 Hz and disengage the 400 Hz high-pass filter from the audio analyzer. Verify that the audio level is –1 dB ("0.7 dB) relative to the level measured in step 3.

5. Change the frequency of the audio generator to 10 kHz and reengage the 400 Hz high-pass filter. Verify that the audio level, relative to that measured in step 3, is 0 dB, "1 dB.

If the system components pass these tests and the microphone is

6Preliminary Tests

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Shure T1 Body-Pack Transmitters

Disassembly and Assembly

To access the printed circuit (pc) board, disassemble the transmitter.

CAUTION

Observe precautions when handling this static-sensitive device.

Disassembly

1. Slide open the battery-compartment cover and remove the battery.

2. With a #1 Phillips screwdriver, remove the four screws securing the back of the case, and set them aside.

3. Carefully separate the top and bottom halves of the case to expose and lift out the pc board. (If you have trouble separating the case, carefully slit the label covering the case separation inside the battery compartment.)

Reassembly

Reassemble the T1 Transmitter as follows:

1. Presenter connector into J104.

2. Place the pc board in the bottom half of the case.

3. Slide the battery-compartment cover into its slot.

4. Align the rubber grommets (antenna, lavalier) while positioning the top half of the case over the bottom half.

5. Make sure the two sections are properly seated before securing them with the four Phillips screws.

T1P transmitter only: Plug the lavalier microphone

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Disassembly and Assembly

Shure T1 Body-Pack Transmitters

Converting a T1P to a T1

Because direct replacements for the lavalier microphones used in

T1P are no longer available, the best way of replacing the micro-

the phones in these earlier units is to replace the lavalier header with a male

Q-G connector, which will allow the unit to accept a WL93 or other

Tini microphone that has a mating connector. Changing the connectors in effect converts the

Parts Needed

Microphone with a female Tini Q-G connector (e.g., Shure WL93). Part order RPW262 for all the following items:

T1P into a T1 unit.

S male Tini S spacer S nut

Q-G connector with a pcb assembly

Conversion Procedures

1. After separating the two halves of the case, remove the pc board and the microphone. Pull the female connector wired to the microphone from the pcb header, J104.

2. Remove the header by unsoldering its four pins from the bottom of the pcb (the side with fewer components). Make sure the four holes in the pcb are open.

3. Orient the pcb assembly with the top (major-component) side up, the switches and

4. Pull off the pre-cut insulation from the ends of the connector assembly’s ribbon cable. From the top of the transmitter board, insert the cable wires into the four holes vacated by the header: the black coded lead goes into the hole nearest the right edge of the pcb (towards the pcb number).

5. Solder the wires to the bottom of the pcb and cut off the excessive leads.

LEDs to the left, and the antenna to the right.

6. After replacing the transmitter’s pcb in the bottom half of the case, insert the connector into the front slot. Place the spacer and start the nut on the part of the connector that protrudes from the case.

7. After completing the reassembly, tighten the nut on the Tini connector.

8Disassembly and Assembly

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Q-G

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