Shure T1 User manual

Shure Incorporated

222 Hartrey Avenue

Evanston IL 60202-3696 U.S.A.

T Wireless System

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

25–1016–1 (CC)

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 up-

date 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.

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

INSERT

these new Revision pages into the

T1 Service Manual

Page 22 Page 22

1Characteristics

25C1016 (CC)



T1/TC1 Body-Pack Transmitters

25C1016 (CC)

Characteristics

General This section tells how to service and align the T1G, T1, TC1, and the

discontinued T1PBody-Pack Transmitters (Figure 1). These single-chan-

nel, crystal-controlled units operate in the 169 MHz to 216 MHz VHF

Band.

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Guitarist T1G

and TC1 Trans-

mitter

Presenter T1

Transmitter

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Presenter T1P

Transmitter

(discontinued

model)

Figure 1.

1. Phone jack 1/4Ȃ(guitar or headset input)

2. Antenna

3. Tini “Q-G”(Lavalier, headset, WA302 input)

4. Lavalier microphone

Service Note: Shure recommends that all service procedures be

performed by a factory-authorized service center or returned directly

to Shure Brothers Inc.

Licensing: Operation may require a user license. Frequency or

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

Contact your country’s communications authorities.

E1999, Shure, Inc.

Printed in U.S.A.

Shure T1 Body-Pack Transmitters

2Characteristics 25C1016 (CC)

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 (T1G), an attached microphone (the

discontinued model T1P), or a four-pin, Tini Q-G, connector (T1):

SPin 1: Ground

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

crophones

SPin 3: Audio input

SPin 4: 20 kΩload resistor connected to pin 3 for Shure electret

microphones

Preamplifier Stage: This is centered in one section of the operation-

al amplifier (U102C). An externally accessible potentiometer (R125) ad-

justs the voltage gain of this stage over a 40 dB range.

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 NE571Dintegrated circuit compandor

(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 am-

plifier U102B, operating as a two-pole, active, low-pass filter, restricts the

bandwidth of the system to audio frequencies.

Limiting: PNP transistors Q103 and Q104 limit the level of the audio

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 LED Drive Circuits: The NE571D’s identical second

channel (U101B) supplies regulated, low-noise 5 Vdc bias to various

audio and RF circuit points. Transistor Q105 provides “reverse battery

protection”to the circuit. Q106 drives LED D101 (“Power On”), and Q107

drives LED D102 (“Low Battery”).

RF Section Audio Input: Processed audio enters R217, an internal potentiom-

eter that is adjusted for 15 kHz deviation (100% modulation) when the

audio section provides a –2.2 dBV, 1 kHz tone.

Oscillation: The audio then goes to varactor diode D201, which is

part of the modulated oscillator-tripler stage (Q201). The latter’s base-

emitter circuit operates as a crystal-controlled Colpitts oscillator in the

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

series resonance by the series combination of frequency-netting coil

Shure T1 Body-Pack Transmitters

3Characteristics

25C1016 (CC)

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

C230.

Frequency and Temperature Stability: To ensure frequency sta-

bility despite changes in the battery voltage, regulated 5 Vdc bias is ap-

plied to the varactor diode and to the base of Q201. Temperature com-

pensation 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 MHz) by L205, C225, C234,

L202, C217, and C233. (The latter components also form a capacitively-

tapped 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 cir-

cuit tuned to the output frequency (for example, 180 MHz). In this case,

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.

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 MN1604, is recommended).

Voltage Measurements: With 9 Vdc applied to the unit, the fol-

lowing voltages should appear at the terminals of the output transistor;

SVc = 8.88 Vdc

SVb = .450 Vdc

SVe = .473 Vdc.

SBase current = .29 mAdc

SEmitter current = 21.5 mAdc

SCollector current = 21.8 mAdc

SPower input = 183 mW

The output power is +16.5 dBm (44.7 mW) into a 50 Ωload, at a fre-

quency of 169.445 MHz. At the minimum acceptable battery voltage of

6 Vdc, the final collector current drops to 15 mAdc and the output power

declines to +13.9 dBm (24.4 mW).

Shure T1 Body-Pack Transmitters

4Characteristics 25C1016 (CC)

Antenna: This is a quarter-wavelength, permanently attached, flex-

ible wire. The ground plane of the circuit serves as an untuned counter-

poise 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 opera-

tion, the collector of each RF stage is separately decoupled from the

9-volt supply by ferrite chokes, resistors, and bypass capacitors. The

base circuits are similarly decoupled except that they use resistor-capac-

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

ate.

Shure T1 Body-Pack Transmitters

5Preliminary Tests

25C1016 (CC)

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”com-

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

there is a strong indication that the customer is using the product incor-

rectly (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 cus-

tomer 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 micro-

phone on-hand for testing) and perform the audio tests in this section.

Functional Tests

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 at-

taching 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 Ωcable 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 RF circuits are

working as designed.

Audio Tests 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.

Shure T1 Body-Pack Transmitters

6Preliminary Tests 25C1016 (CC)

2. Set the RF generator as follows:

Amplitude: –20 dBm

Modulation: 1 kHz

Deviation: 15 kHz

Frequency: T1 operating frequency

3. Connect the audio from the unbalanced output to the audio ana-

lyzer with a 3.3 kΩload. Turn the Volume control all the way up.

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

Saudio level is 400 mVrms ("90 mV)

Sthd = <0.75%

B: Check the Transmitter

1. Disconnect the signal generator from the receiver. Monitor the

receiver’s unbalanced audio output with a 3.3 kΩload 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 body-

pack input.

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:

Sthe amplitude from receiver’s unbalanced output equals

400 mVrms ("90 mV)

Sthd = <0.75%

4. Change the frequency of the audio generator to 100 Hz and dis-

engage 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 re-

engage the 400 Hz high-pass filter. Verify that the audio level,

relative to that measured in step 3, is 0 dB, "1 dB.

Units That Pass If the system components pass these tests and the microphone is

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.

Shure T1 Body-Pack Transmitters

7Disassembly and Assembly

25C1016 (CC)

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 bat-

tery.

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 ex-

pose 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 T1Ptransmitter only: Plug the lavalier microphone

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.

Shure T1 Body-Pack Transmitters

8Disassembly and Assembly 25C1016 (CC)

Converting a T1Pto a T1

Because direct replacements for the lavalier microphones used in

the T1Pare no longer available, the best way of replacing the micro-

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

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

microphone that has a mating connector. Changing the connectors in

effect converts the T1Pinto a T1 unit.

Parts Needed

Microphone with a female Tini Q-G connector (e.g., Shure WL93).

Part order RPW262 for all the following items:

Smale Tini Q-G connector with a pcb assembly

Sspacer

Snut

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 mi-

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

4. Pull off the pre-cut insulation from the ends of the connector as-

sembly’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 exces-

sive leads.

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 Q-G

connector.

Shure T1 Body-Pack Transmitters

9Service Procedures

25C1016 (CC)

Service Procedures

Reference Material

The Shure Wireless Systems: T Series User’s Guide provides a de-

scription, information on operation and troubleshooting, and technical

data.

Special Equipment

The Wireless Service Equipment manual covers the standard items

needed for servicing the transmitters. If you do not have the modified

SC4 receiver described there, you will need an appropriate receiver (usu-

ally T3 or T4) to verify that the transmitter is working properly.

System Operating Frequencies

Each transmitter circuit board is marked with a group letter (A, B, C,

or T) that identifies the range of frequencies on which the transmitter can

operate. Table 1 shows the Group Letter and its associated frequencies.

Note that this chart applies only to the T1 series.

Table 1

(90_8552F) Pc Board Groups

Group Frequency Range

A 169.000–183.975 MHz

B184.000–198.975 MHz

C199.000–215.975 MHz

T“AC,”“V,”& “W”frequencies

Used with pcb assembly 90_8552F

(pcb marking 34A8459F)

Table 2 provides information for identifying the system frequency.

The Crystal Letter Code, when used with the appropriate Shure model

number, identifies a specific operating frequency for both transmitters

and receivers. Note that, although a Crystal Letter Code always desig-

nates a specific frequency, it may be used with different Group Letters on

other products.

Group T: Beginning in July 1995, “V”and “W”frequencies, formerly

assigned to the “A”board, were reassigned to a newly designated “T”

board (see the “Audio Alignment”subsection in “Service Procedures”).

Shure T1 Body-Pack Transmitters

10Service Procedures 25C1016 (CC)

Table 2

T1 Series System Operating Frequencies

Group Crystal Code Freq. (MHz)

T V 169.445

T AC 170.245

T W 171.845

A CA 176.200

A CC 177.600

A CE 182.200

A CF 183.600

B CG 186.200

B CL 192.200

C CQ 202.200

C CV 208.200

Changing the Frequency

The operating frequency of the T1 transmitter may be changed with-

in a specific group by changing the crystal on the pc board. (For Group

information, see the preceding section.) Check the transmitter for proper

operation before attempting to change its operating frequency. After in-

stalling the new crystal, perform the alignment procedures. Then run an

operational test to ensure the transmitter 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 their nominal oscillating frequency,

not a letter code, you can use the following equation to determine

the frequency at which a transmitter will operate with a given crystal:

Carrier Frequency = (9 nominal crystal freq. in MHz) –.09

Alignment The RF and audio alignments are generally 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 test conditions apply unless otherwise specified (see

Figure 2):

SAn external 9-volt supply is connected to the battery terminals

(J101 and J102).

SThe Power On/Off switch is off.

SThe Mute switch is set to “Mute.”

Shure T1 Body-Pack Transmitters

11 Service Procedures

25C1016 (CC)

SThe Gain pot (R125) is preset to its midpoint.

SThe 400 Hz high-pass and the 30 kHz low-pass filters on the

audio analyzer are activated.

Spectrum Analyzer

Frequency Counter

T1P(Connector J104)

Pins

T1G(1/4I

phone jack,

J103)

LED (red)

“Low Battery”

(D102) Mute

switch

(S101)

Power On/Off

switch (S102)

“Power On”

LED (green)

(D101)

Battery

terminals

J101 –

J102 +

TP4

TP3

C215C217Y201

L209

R217

R125

R130

ÊÊ

34T1 (Tini “Q-G,”J201—solder side)

T1 (Tini “Q-G”) pins:

1: Ground

2: +5 V

3: Audio

4: 20 kΩto ground (connected

to pin 3 in the microphone)

Figure 2. Pc Board: Key Parts Locations

Test Cable Use a 50 Ωcoaxial test cable to connect the pc board with various

test equipment (see Figure 2). To construct the 50 Ω test cable, see the

Wireless Service Equipment manual.

1. Unsolder the antenna lead from the pc board.

2. Attach the center conductor of the 50 ΩRG174 cable to the antenna

solder pad, and the shield to ground.

3. Turn on the T1.

Shure T1 Body-Pack Transmitters

12Service Procedures 25C1016 (CC)

TP2

Test Points

TP1Audio In, J104, pin 3, Model T1-P.

TP2Audio In, J103, center conductor

of 1/4-in. phone jack, Model T1-G.

TP3Audio

TP4Antenna Output

TP5Intermediate Output

TP69 Vdc

TP75 Vdc

TP8(+) Battery

TP9(–) Battery

TP1TP5TP4

TP3

TP9 (–)

TP8 (+)

TP6

TP7

Limiter components

(not in all units)

Figure 3. Pcb Side 1

Display Checks 1. Connect the 9 Vdc power supply: the green LED should glow.

2. Reduce the power supply voltage to 6 Vdc: the red LED should

glow.

3. Return the power supply voltage to 9 Vdc.

4. Verify that 9 Vdc 〈±0.35 Vdc) is present at TP6.

5. Verify that 5 Vdc 〈±0.25 Vdc) is present at TP7.

RF Alignment A: RF Power and Frequency

1. Connect the 50 Ω output cable to the spectrum analyzer. Make

sure S101 is in the “Mute”position.

2. Set the spectrum analyzer as follows:

SCenter Frequency: transmitter’s

SSpan: 1 MHz

SReference Level: +20 dBm

SScale: 10 dB/div

3. The output power should measure 15 dBm ( ±2 dBm) taking into

account cable losses. If the power is within specification, skip to

step 6.

4. Adjust C217 for maximum (peak) output power on the spectrum

analyzer.

Note: Once the signal is close to its maximum, setting the spec-

trum analyzer scale (under the amplitude menu) to 2 dB/div may

make fine adjustments easier.

5. Adjust C215 for maximum output power on the spectrum analyz-

er. The output power should measure 15 dBm (±2 dBm) taking

into account cable losses.

Shure T1 Body-Pack Transmitters

13 Service Procedures

25C1016 (CC)

6. Connect the 50 Ωoutput cable to the frequency counter. If the

frequency is off by more than 5 kHz, adjust L209 to set the carri-

er frequency to FC ±1 kHz.

7. Reconnect the 50 Ωoutput cable to the spectrum analyzer. Con-

firm that the output power remains within specification. If neces-

sary, readjust C217 and C215.

B: Spurious Emissions

1. Set the scale on the spectrum analyzer back to 10 dB/div.

2. Check the level of spurious emissions up to 1 GHz. Set the start

frequency of the spectrum analyzer to 10 MHz and the stop fre-

quency to 1 GHz. All spurs must be at least 35 dB below the

carrier level. If necessary, adjust C217 and C215 until the power

and spurious response are both within specification.

C: Current Drain

1. Using a milliammeter, make sure that the transmitter’s current

drain is less than 35 mA. If it is too high, try detuning C215, tak-

ing care that the power and spurious response remain within

specification.

2. Disconnect the power supply from the T1.

3. Unsolder the 50 ΩRG174/Utest cable, and resolder the antenna

lead to the RF board.

Audio Alignment This section continues the procedures of the preceding subsections.

D: Gain

1. Reconnect the power supply to the T1, and set its Mute switch to

“On.”

Set the audio analyzer output as follows:

Frequency: 1 kHz

Amplitude: 70 mV

2. Connect the audio analyzer’s output to the transmitter’s micro-

phone input. Select the cable with the proper termination:

(a) T1: Tini Q-G (quick-ground) connector

(b) T1G:1/4-in. phone plug

J104; shield to ground

3. Adjust the Gain pot (R125) for 775 mVac, ±10 mVac (0 dB,

±0.1 dBu) at TP3 (turning counterclockwise increases the gain).

Record the voltage at this setting.

Note: At this point you may want to press the audio analyzer’s

Log/Lin button (to measure logarithmically) and activate the Ra-

Shure T1 Body-Pack Transmitters

14Service Procedures 25C1016 (CC)

tio button to perform the relative measurement in the next sub-

section.

out Audio Analyzer in

T1P(connector J104)

Pins

T1G(1/4I

phone jack,

J103)

LED (red)

“Low Battery”

(D102) Mute

Switch

(S101) Power On/Off

Switch (S102)

“Power On”

LED (green)

(D101)

Battery

Terminals

J101 –

J102 +

C215C217Y201

L209

R217

R125

R130

TP4

TP3

Receiver

34T1 (Tini “Q-G,”J201—solder side)

Figure 4. Audio Test Configuration for T1

E: Audio Frequency Response

1. Change the frequency of the audio analyzer to 100 Hz.

2. Deactivate the audio analyzer’s 400 Hz high pass filter.

3. Check that the audio level is equal to –1 dB (0.5 dB) relative to

the level measured at TP3 in step 3 of subsection D (“Gain”).

4. Activate the 400 Hz high pass filter on the audio analyzer.

5. Change the frequency of the audio analyzer to 10 kHz. Because

the limiter circuitry was removed from most units made after

June 1995, the audio level will vary with the unit you have:

SAll “V”And “W”frequency units: +3.1 dB (±0.5 dB)

SAll units made through 6/95: +3.1 dB (±0.5 dB)

SAll non-“V”and “W”units made after 6/95: +4.85 dB

(±0.5 dB)

Note: pc boards with the limiter components (see Figure 3)

should have the lower (+3.1 dB) audio output level.

6. Disengage the ratio function.

Shure T1 Body-Pack Transmitters

15 Service Procedures

25C1016 (CC)

F: Deviation Reference Voltage

1. Turn off the transmitter.

2. Set the RF signal generator as follows:

(a) Enter the carrier frequency.

(b) Select FM modulation and enter the following:

Modulation Source: Int 1 kHz

FM Deviation: ±15 kHz

Amplitude: –38 dBm

3. Select a receiver for the T1, making sure it is set to the same

frequency as the transmitter. Disconnect the receiver’s antenna

(non-diversity) or antennas (diversity).

4. Solder the 50 Ωcable to the receiver’s antenna pads:

T3: Center conductor to TP1, and shield to TP2

T4: Center conductor to TPA1, and shield to TPA2

5. Connect the BNC end of this cable to the output of the RF signal

generator.

6. Set the Volume control on the front panel of the receiver to its

maximum position (fully clockwise). Then turn on the receiver

and set its Squelch control to the midpoint position.

7. Measure the rms voltage developed across the unbalanced out-

put of the receiver. You should find approximately 775 mVac.

This is the audio output voltage that corresponds to a deviation

level of 15 kHz.

Record this voltage as the deviation reference voltage.

Note: At this point you may want to press the audio analyzer’s

Log/Lin button (to measure in dBm) and activate the Ratio button

to perform the relative measurement in the next subsection.

G: Deviation Adjustment

1. Turn off the RF switch on the RF signal generator.

2. Remove the test cable from the receiver and reconnect the an-

tenna(s) to the receiver board.

3. Turn on the T1 and set its Mute switch to “On.”

4. Reconnect the output of the audio analyzer to the input of the

T1.

5. Reset the frequency of the audio analyzer to 1 kHz. Make sure

that 775 mV is still present at TP3.

6. Measure the voltage at the unbalanced output of the receiver.

Adjust R217 for 0 dB (±1 dB) relative to the deviation reference

voltage measured in step 7 of the preceding subsection.

Shure T1 Body-Pack Transmitters

16Service Procedures 25C1016 (CC)

7. Set the audio analyzer to measure distortion. Verify that the au-

dio distortion at the unbalanced output of the matching receiver

is less than 0.5%. If necessary, adjust R130 to obtain minimum

distortion.

Note: For T1Gtransmitters Only: After completing the alignment,

turn the audio Gain potentiometer (R125) all the way down (fully

clockwise as viewed from the top side of the circuit board).

Shure T1 Body-Pack Transmitters

17 Bench Checks

25C1016 (CC)

Bench Checks

Dc Power

nVerify that 9 Vdc (±0.35 Vdc) is present at TP6. If this voltage is

low, trace the circuitry back to the power supply to see where the

loss occurs. Check:

Spower switch

Sbias on Q105

SL101

Scircuit-board ground for 0 V

nIf you have a short to ground from 9 V, try isolating different parts

of the circuit. Narrow it down to the RF or audio section. Look for

foil shorts, solder bridges, and capacitors that have been

installed backwards.

nCheck for 5 Vdc (±0.25 Vdc) at TP7 (pin 7 of U101). If the correct

voltage is not present, check:

Spin 13 of U101 for 9 V

Svalues of R133, R135, and R137

Audio All the steps in this section comprise a methodical way of determin-

ing where the audio signal is being interrupted:

nCheck for audio at pin 7 of U102. If it is not present, check that

the dc bias at pins 5, 6, and 7 of U102 is `4.5 Vdc (half the lev-

el of the supply voltage). If the correct voltage is not present:

STrace the circuitry: this bias derives from the 9 V line through

voltage divider R103 and R105, then through R106 to pin 5.

SLook for foil shorts, incorrect parts, and bad connections.

nIf there is audio at pin 7 of U102 but not at pin 14, check the dc

bias at pins 12 and 13 (`1.8 Vdc) and pin 1 (`3.7 Vdc). If the

correct voltage is not present:

STrace the circuitry: this dc bias proceeds from pin 9 of U101

through R107 to pin 12 of U102.

SCheck (a) the parts in the feedback path from pin 14 to

pin 13, (b) the parts connected to pin 7, and (c) the connec-

tions from U102 to U101.

nCheck the connections from pin 14 of U102 to the next stage, to

the limiter (Q103), and to pin 15 of U101.

Shure T1 Body-Pack Transmitters

18Bench Checks 25C1016 (CC)

nCheck the bias voltage (`4 Vdc) on pins 8, 9, and 10 of U102. If

the correct voltage is not present:

SMake sure the Mute switch is set to “On.”

STrace the bias circuit from the 5 V line through R104 to

pin 10 of U102.

SCheck the values in the feedback path from pin 8 to pin 9 of

U102, and the path to Q104 and pin 16 of U101.

Frequency Problem

nMake sure the RF carrier is at least 10 dB higher than the spuri-

ous emissions, to allow the frequency counter to lock on.

nCheck L209 for the proper group and make sure its core is not

cracked.

nMake sure the crystal (Y201) has the correct frequency.

nCheck the dc bias for Q201 against the readings of a unit known

to be operating correctly.

nMake sure that D201 is the correct varactor and has 5 Vdc on its

cathode.

nCheck the parts and values of the oscillator circuit (from TP3 to

TP5).

nLook for shorts and opens.

Low Output Power

nCheck the carrier output power after the oscillator stage (TP5). If

there is no signal, refer to the preceding subsection, “Frequency

Problem.”

The remaining steps perform basically similar diagnostics for each of

the three RF stages:

nStage 1: Make sure that rotating C217 360 degrees in either di-

rection produces two separate peaks in the carrier output ampli-

tude. If there is only one peak, check the color (value) of C217

and the values of L205, C225, C234, L202, and C233. Check

the bias on Q201. Lastly, replace Q201.

nStage 2: Make sure that rotating C215 360 degrees in either di-

rection produces two separate peaks in the carrier output ampli-

tude. If there is only one peak, check the color (value) of C215

and the values of L204, C237, C236, L207, C235, C222, and

C226. Check the bias on Q203. Lastly, replace Q203.

nStage 3: Check the dc bias on Q204 and the values of all the

parts from the base of Q204 to TP4. Lastly, replace Q204.

nIf the power is slightly low and the spurious levels are high,

check for wrong or open coils at L202, L207, and L206.

Shure T1 Body-Pack Transmitters

19 Bench Checks

25C1016 (CC)

Excessive Current Drain

nTry readjusting C215 for lower current drain while maintaining

output power to specification. If the current drain is still exces-

sive, check for the following:

Sshort

Swrong resistor value

Sshorted capacitor

nAs a last resort, try changing Q204.

Deviation

nIf R217 cannot be adjusted to obtain a "15 kHz deviation, try to

isolate the problem to the audio or RF section by doing the fol-

lowing:

SIf TP3 does not measure –2.2 dBV (775 mV), refer to the

“Audio”subsection, above.

SIf TP3 has the right level, check R217, C220, C227, R208,

R216, D201, R209, L209, and C214. Also make sure that

the cathode of D201 is being supplied with a 5 Vdc bias from

the 5 V Line through R216 and R208. The value of C214 is

critical to the deviation sensitivity.

nAs a last resort, try replacing D201 and Y201.

nMake sure the carrier is good: you need that to get any devi-

ation.

Distortion

nMake sure the analyzer’s 400 Hz high-pass and 30 kHz low-

pass filters are ”In.”

nPin 9 of U101 should read about 1.8 Vdc.

nAs you turn R130, the dc level on its wiper should change from

about 1.5 V to 3.5 V. If it does not, check R129, C125, R130,

R141, R140, R126, and the parts tied to pin 9 of U101.

nCheck the audio level.

nLastly, replace D201 and Y201.

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