Shure T1, TC1 Service 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)
1
Characteristics
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 T1P Body-Pack Transmitters (Figure 1). These single-channel, crystal-controlled units operate in the 169
MHz to 216 MHz VHF
Band.
Á
Guitarist T1G
and TC1
Trans-
mitter
Presenter T1
Transmitter
Á
ББББББ
ББББББ
ББББББ
Presenter T1P
Transmitter
(discontinued
model)
1
2
3
4
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):
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.
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
NE571D integrated 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 amplifier 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 potentiometer 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 baseemitter 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
3
Characteristics
25C1016 (CC)
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
MHz) by L205, C225, C234,
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
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 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
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, 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
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-capacitor (
R-C) networks, whose higher-impedance levels are more appropri-
ate.
Shure T1 Body-Pack Transmitters
5
Preliminary 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” complaints, 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 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
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
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 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%
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.
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.
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
7
Disassembly 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 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
T1P transmitter 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 T1P to a T1
Because direct replacements for the lavalier microphones used in
the
T1P are 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
T1P into 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:
S male Tini
Q-G connector with a pcb assembly
S spacer
S nut
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
LEDs to the left, and the antenna to the right.
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.
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.
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