Shure slx2 User Manual
SLX2 Wireless Transmitter Service Manual
SLX2 WIRELESS HANDHELD TRANSMITTER
PRODUCT DESCRIPTION
The Shure Model SLX2 is a µP (microprocessor) controlled frequency agile UHF
handheld transmitter operating over the frequency range of 518 to 865 MHz (in eight
different 24 MHz-wide frequency bands). The transmitter will operate for a minimum of 8
hours using two "AA" alkaline batteries. The User Interface includes "mode" and "set"
buttons, and an LCD that displays battery status, group/channel, and transmitter/
receiver frequency synchronization. The SLX2 has a plastic enclosure, and utilizes an
internal antenna for optimum range and reliability. This product is intended for use in
entry-level presentation, installed, and performance markets.
25A1090
FEATURES
SLX
mute select
1. Frequency agile; microprocessor controlled. Model number extensio n determines frequency band of operation.
2. Minimum of 12 compatible systems per SKU in the U.S. Additionally, a minimum of 12 compatible systems in the top 50 U.S. markets across all three domestic SKU's (H5, J3, and L4).
3. Operating frequency programmable locally or from the receiver using a built-in IR link.
4. Designed for use with "AA" alkaline batteries (2 required). May also be used with rechargeable "AA"
batteries. Note: battery condition indicator is calibrated for alkaline batteries and may not be accurate with rechargeable types. Electrical reverse battery protection is included.
5. Minimum battery life of 8 hours with new "AA" alkaline batteries.
6. Designed for use with SM58, BETA 58, SM86, and BETA 87A&C microphone heads. Compatible with "active load" or standard heads (active load circuitry to be incorporated in heads).
7. Tone key squelch.
8. Power/Mute and Select buttons with LCD display for frequency group/channel selection and control. LED backlight for easy reading of LCD display.
9. Bicolor, green/red LED for power "on" and low battery, mute and infrared link indications.
10. Rugged plastic construction.
11 . Utilizes Shure Patented ARC (Audio Reference Companding) audio processing.
©2006, Shure Incorporated
25A1090 (Rev.3)
DETAILED DESCRIPTION
1
2
SLX
3
4
mute select
5
Features
1 Interchangeable microphone head (SM58 pictured)
2 Power / Infrared (IR) / Mute indicator
Green: ready
Amber: mute on
Flashing red: IR transmission in process
Glowing red: battery power low
Pulsing red: battery dead (transmitter cannot be turned off until batteries are changed)
3 LCD screen
4 On-off / mute switch
Press and hold to turn on or off. Press and release to mute or unmute.
5 Select switch
6IR port
Receives infrared beam to synchronize frequencies. When using multiple systems, only one
transmitter IR port should be exposed at a time.
SLX
mute select
6
Adjusting Gain
Access the gain adjustment switch a by unscrewing the head of the microphone.
Two gain settings are available on the SLX2. Choose a setting appropriate for vocal volume and for the performing environment. Use the tip of a pen or a small screwdriver to move the switch.
•
0dB:
For quiet to normal vocal performance.
•
–10dB
: For loud vocal performance.
BIAS
AUDIO
-10dB
0dB
a
b
SLX
25A1090 (Rev.3)
mute select
2
a
MASTER LIST
GROUP
i8 i8
b
MASTER LIST
GROUP
i8 i8
Incompatible
CHANNEL
select
Incompatible
CHANNEL
select
SLX2 Transmitter Programming
Manually Select a Group and/or Channel
select
5
1. Press and hold the select button until the GROUP and CHANNEL displays begin to alternate.
a
2. To change the group setting, release the select button while GROUP is displayed
. While GROUP
is flashing, pressing select increases the group setting by one.
b
3. To change the channel setting, release the select button while CHANNEL is displayed
. While
CHANNEL is flashing, pressing select increases the channel setting by one.
Incompatible
MASTER LIST
CHANNEL
GROUP
i8 i8
Incompatible
MASTER LIST
CHANNEL
GROUP
i8 i8
Incompatible
MASTER LIST
CHANNEL
GROUP
i8 i8
Incompatible
MASTER LIST
CHANNEL
GROUP
i8 i8
Lock or Unlock Transmitter Settings
select
+
Press the mute/ and select buttons simultaneously to lock or unlock the transmitter settings. When
locked, the current settings cannot be changed manually. Locking the transmitter does not disable in-
frared synchronization.
Battery Status
Indicates charge remaining in transmitter batteries.
Master List Indicator
Indicates that a master list frequency is currently in use. No group or channel information is displayed.
Note: the transmitter cannot be used to change master list settings.
INCOMPATIBLE Frequency Warning
The INCOMPATIBLE warning indicates that the receiver and transmitter are transmitting on different
frequency bands. Contact your Shure retailer for assistance.
25A1090 (Rev.3)
3
AUDIO/RF BLOCK DIAGRAM
A
Converte
A
A
A
IR
Photodetector
LCD
LCD
Driver
EPROM
Audio Input
(mic head)
32.768
LPF
Supply
Microcontroller
Channel
Select,
A Battery
User Gain
Control Switch
Tone Key
RF
mp
DC-DC
r
Preemphasis
Frequency
Synthesizer
control
RF Muting
Pad
0-4 dB (Band
dependent)
+5V DC
Source
VCA
Compressor
udio Muting
RF
mp
2-pole,
17kHz,
LPF
Limiter
Deviation Trim
and Tone Key
Sum Amp
RMS
Detector
Pad
0-4 dB (Band
dependent)
VCO (Carrier
Range)
Frequency
Synthesizer
Loop
Filter
16
MHz
CIRCUIT DESCRIPTION
AUDIO CIRCUIT DESCRIPTION
AUDIO SECTION
Audio enters the transmitter board through pin 4 of the mic-jack board connector (CON100).
Pin 2 of the connector provides 5 Vdc bias for the mic head. Pin 6 supplies the ground connection. The audio preamp (IC150-2) provides either 0 or 10 dB of gain (user switchable via
SW100). Capacitor C140 couples the signal into a pre-emphasis network formed by R140, R141,
and C141.
Next, the audio signal enters the patented Shure ARC™ processor. The main elements in this
section are the VCA (IC100-5) and the RMS Detector (IC100-4). The VCA, or Voltage Controlled
Amplifier, is a DC controlled amplifier. Following the VCA, the signal enters a 3-pole 17kHz lowpass filter stage (IC100-2) that protects the RMS detector from energy above the audio band.
Next, the signal is coupled to the RMS detector (IC100-1), which converts it to a DC voltage. A
+1 dB increase at the input to the detector produces a +6 mV increase at its output. The detector
output is fed to the compression threshold stage (IC150-2). This stage provides the transition
from uncompressed to compressed signal. At low levels, the audio is uncompressed because
diode D169 is turned off. As the AC level increases, the output of IC150-2 decreases enough to
turn the diode on. As D190 conducts, the compression ratio changes from 1:1 to 5:1. Once D190
is turned fully on, the audio compression ratio remains fixed at 5:1. An additional diode in the bias
25A1090 (Rev.3)
4
network (D162) provides temperature compensation for changes in the VY, or "cut-in" voltage of
D190. After the compression threshold stage, the DC control signal is amplified by a 40 dB fixed-
gain stage (IC100-5). It is then sent to the VCA control voltage input (EC+).
Following the ARC™ processor section, the audio signal must pass through a muting network
consisting of R199, R200, C205, and Q205. A trim pot (TR200) allows the audio deviation level
to be set. Next, audio enters the tone key summing amp (IC150-4). Here, tone-key is added to
the audio before passing to the RF section for transmission. The tone key signal is used in the
receiver to provide audio output only when the tonekey signal is present with the transmitted signal; therefore, if the tone key or the transmitter is turned off, the receiver will be muted. The tone
key squelch will eliminate receiver noise associated with loss of the carrier, which usually sounds
like a "pop". The tone key signal is generated by a square wave from the mP (IC300). It is then
filtered by active filter stage Q185 and attenuated by R188/R189 (under µP control) before being
fed to the summing amplifier. The combined audio/tone-key signal is then sent to the VCO
through R504.
POWER SECTION
Two "AA" batteries supply power to the transmitter through FET Q410, which provides electrical reverse battery protection. Next, power enters switching boost converter IC400, which supplies regulated 5V power. To turn on the transmitter, SW325 shorts the base of Q480 to ground,
enabling the converter and powering up the unit. The microprocessor keeps Q480 disabled until
shutdown.
Power is turned off by a "shutdown" signal from the microprocessor, which can be initiated
manually by the user (by holding down SW325 for 2.2 seconds) or automatically by the system
(e.g., when the battery is too weak for proper operation). At this time, the microprocessor enables
Q480 and shuts down the converter. When the unit is off, Q480 and its bias circuitry draw less
than 30 µA, so the effect on battery life is negligible. The converter and microprocessor are disabled.
shutdown, and will not turn the system back on until a voltage greater than 2.25 V is present. The
hysteresis keeps the system in a controlled state when the batteries are low, and also helps prevent weak batteries from being used from the start.
RF CIRCUIT DESCRIPTION
frequency modulation. Processed audio enters the VCO through a passive "reflection" network
before being applied to the varactor diode (D500) through choke L503. The VCO is shielded to
prevent external RF fields from affecting its operation, and to help control radiated emissions of
its harmonics. Power for the VCO and PLL circuitry is supplied by the main 5 V regulator. Power
and signal lines in the VCO area are heavily decoupled and bypassed to remove noise.
range of approximately 1 to 4 volts. The VCO employs separate stages for the oscillator (Q502)
and buffer (Q501) to minimize phase noise and load pulling. The VCO output is isolated by capacitive and resistive dividers, before being applied to the frequency control pin of the PLL synthesizer (IC501) through C538. The synthesizer's internal circuitry divides the RF signal down as
necessary to achieve a tuning precision of 25 kHz. The synthesizer circuit contains a quartz-controlled reference oscillator operating from a 16 MHz reference crystal (Y801) that is adjusted by
means of trimmer CV501. The transmitter output frequency is user selectable in groups of compatible channels within each of the eight available bands. Frequency selection is made via microprocessor controller IC300, which interfaces with the user by means of the Group and
Channel switches, SW324 and SW325. The output of the synthesizer is a series of pulses that
are integrated by a passive loop filter consisting of C532, R514, C533, R513, and C531 to produce the control voltage signal.
of R602, C614, and L610. R600 and R603 provide base bias for the transistor, while R605 sets
its operating current. RF choke L600 provides power and decoupling for the stage, in conjunction
LOW BATTERY SHUT DOWN:
A software battery shutdown routine allows the battery supply to run down to 2.05 V before
RF SECTION
The system block diagram is shown above. The SLX2 uses a PLL system with direct carrier
The VCO has a tuning bandwidth of more than 30 MHz on all bands, with a tuning voltage
The VCO output is coupled to the RF buffer stage (Q600) by a matching network consisting
25A1090 (Rev.3)
5
with C600 - C604. The collector of Q600 feeds the power amplifier stage via an impedance
matching network consisting of L602, C611, and C618.
The bias voltage for the RF power amplifier (Q601) is supplied by R601 and R604. Its operating current is controlled via emitter resistor R606. RF choke L601 provides power and decoupling
for the stage, in conjunction with C605-C609. For Japanese systems only, the output power is
trimmed via TR640. L603, C612, and L604 provide the output impedance matching into the low
pass filter, which consists of L604, L605, L606, C615, C616, and C617. The low pass filter output
couples to the battery antenna via C641 and L607. Connector CON640 and C613 are only used
for Japanese (JB) units. Coupling capacitor C610 is used to ensure that both batteries are driven
equally.
The transmitter is capable of delivering up to +15.0 dBm to the antenna (depending
on band and country). During transmitter power-up and frequency selection, the RF
output is muted by bringing the base of Q631 low, which removes bias from Q630
and shuts down power to the RF stages. The RF output is also muted during the
transmitter power-down sequence. This is done so that the carrier signal will not
interfere with other transmissions when the loop becomes unlocked.
DIGITAL CIRCUIT DIAGRAM
Backlight
LED
RF Band
DC Level
Battery DC
Level
Power Mute
Button
Select
Button
Softstart
Shutdown
Microprocessor
(Motorola
MC68HC908GR16)
Power LED
LCD Driver
(Rohm
BU9729k)
Sythesizer
(National
Semiconducter
LMX2335)
RF Power
Tonekey
Squarewave
LCD
VCO
25A1090 (Rev.3)
Infrared
Photodetector
(Sharp GP1U10X)
EEPROM
(MicroChip
93AA46 )
Audio Mute
Tonekey
Level
6
DIGITAL SECTION
ACCESSING DIFFERENT MODES
ATE MODE
If TP_PB0 is held to TP_EGND, or logic level 0, at startup, the microcontroller will enter ATE
Mode. T o ensure proper operation, TP_P A0 and TP_P A1 should be held to TP_EGND at startup.
In ATE Mode, each band has a three test frequencies that are control led by the logic levels at
test points TP_PA0 and TP_PA1.
Frequency TP_PA0 TP_PA1
Low 00
Center 01
High 11
Test Frequencies (MHz) H5 J3 JB L4 P4 Q4 R5 S6
SLX2 Low 518.400 572.400 806.125 638.400 702.100 740.125 800.525 838.100
Center 529.500 583.500 807.500 649.500 714.000 746.325 810.275 851.300
High 541.800 595.800 809.750 661.800 725.900 751.875 819.800 864.800
RF BAND RESISTORS
Two resistors (RA and RB) are responsible to start the microcontroller in a RF band. They determine the voltage at test point TP_RFBAND.
This table shows R
reflect the operating RF band.
's and RB's reference designators and how the voltages at the test points
A
SLX Reference Designators
SLX2
R
A
R
B
R319 R320
This figure depicts the voltage divider feeding the microprocessor analog to digital converter.
.
25A1090 (Rev.3)
7
This table shows the variant resistor values and resulting voltages at TP_RFBAND for each band.
RF BAND Rb TP_RFBAND(+/- 0.10V) H5 1.00k 0.30V J3 2.99k 0.76V L4 4.99k 1.10V R5 7.50k 1.41V S6 12.10k 1.81V P4 18.2k 2.13V Q4 30.1k 2.48V JB 49.9k 2.75V
Note: Voltages are calculated with a 3.30V (+/- 0.10V) reference from the power
supplies. If power section supports less than 3.30V, thresholds need to be adjusted.
µC DECISIONS BASED ON ANALOG VOLTAGES
Continuous Operation Battery Thresholds
BATTERY_A2D RF Level Display Logic Voltage (V)
Measured @ 3V
- dBC >= 2.25
block battery clips
- dBC < 2.25
- dBC < 2.14
-8 dBC < 2.05
Note: There is a dead battery lock voltage set at 2.30 Volts. If the transmitter is powered
on with a voltage of less than 2.30 Volts, the system will lock, forcing the user to either
recharge or replace the batteries. During the dead battery lock out, the battery gauge is
empty and the red led flashes.
25A1090 (Rev.3)
8
NOTES
25A1090 (Rev.3)
9
FUNCTIONAL TEST
REQUIRED TEST EQUIPMENT (OR APPROVED EQUIVALENT OR SUPERIOR MODELS):
Spectrum analyzer or power meter HP8590L/Agilent E4403B/Agilent E4407B Digital multimeter Fluke 87 Audio Analyzer HP 8903B Frequency Counter HP 53181/HP 5385A Power Supply Power Supply must be able to supply 3Vdc
Shielded test lead Shure PT1838F BNC (Male) to BNC (Male) cable (1) Shure PT1838A UA820 Antenna Frequency Dependent Audio Test Head PT1840
Brass Ring PT1838Y
LISTENING TEST
Before completely disassembling the transmitter, operate it to determine wether it is functioning normally and try to duplicate the reported malfunction. Refer to pages 2 and 3 for operating instructions, troubleshooting, and specifications.
Review any customer complaint or request, and focus the listening test on any reported problem. The following, more extensive, functional tests require partial disassembly.
FUNCTIONAL TEST
Refer to the Disassembly section to partially disassemble the transmitter for the following functional tests.
with an internal ammeter.
TEST SETUP
1. Remove the PCB from the handle.
2. Set gain switch to “0” dB.
3. Connect the (+) terminal of the power supply through a milliammeter to the (+) battery terminal and
the (-) power supply terminal to the (-) battery terminal.
4. Connect a DC Voltmeter across the power supply and set the power supply for 3Vdc.
5. Connect the audio analyzer to the microphone via the microphone test head (PT1840) as needed.
DISPLAY TEST
1. Power unit ON.
2. Verify that all display segments are displayed for approximately 2 seconds. This includes a full bat-
tery indication and "1818" displayed for group and channel.
REVERSE BATTERY PROTECTION TEST
1. Adjust power supply to -3.0 ± 0.1 V dc.
2. The current should be less than 0.5 mA.
VOLTAGE REGULATION TEST
With power applied properly, and the unit switched on, measure the DC voltages at the following test points. All test points are located on the top side of the PCB. Refere to the component diagram.
• TPBATT+ (Battery input) = 3 ± 0.2 Volts
• TP5V (Power Converter) = 5 ± 0.2 Volts
• TP3.3V (Power Converter) = 3.3 ± 0.2 Volts
• TPA1 (Audio Preamp) = 2.5 ± 0.2 Volts
• TPA3 (Tone Key Summing Amp (IC150 Pin 14)) = 2.5 ± 0.2 Volts
• TPVREF (IC100 Pin 5) = 2.5 ± 0.1 Volts
25A1090 (Rev.3)
CURRENT CONSUMPTION TEST
1. With +3V applied to the battery terminals and the unit powered on.
2. Verify the current drain is 130 ± 15mA.
10
FREQUENCY RESPONSE TEST
1. Set the audio generator as follows:
•
Frequency = 1 kHz
• Amplitude = -20 dBu
• Filters = 30 kHz LPF
2. With the audio analyzer, probe TPA2 (top side), it should read -3.4dBu ± 0.5dB. Record this level
using the Ratio button. This level will be used as your reference level for the following test.
3. Change the generator's frequency to 100Hz and measure the level at TPA2 to be -2.2dB ± 0.2dB
relative to the 1kHz reference level.
4. Change the generator's frequency to 10kHz and measure the level at TPA2 to be +2.3dB ± 0.2dB
relative to the 1kHz reference level.
5. Disengage the Ratio button.
DISTORTION TEST
1. Set the audio generator frequency to 1kHz with an amplitude of -20.0dBu.
2. Activate the 30kHz LPF on the audio generator.
3. Measure the total harmonic distortion and noise (THD+N) at TPA2 to be less than 0.7%.
RADIATED RF OUTPUT POWER AND FREQUENCY STABILITY TEST
1. Choose any group and channel free of interference. Using a spectrum analyzer with the appropri-
ate-band UA820 antenna, measure the approximate near field radiated power as follows:
• SPAN=100 MHz
• REF LVL=10dBm
• FREQUENCY=(Look at tables on pages 18 thru 23)
2. Extend the UA820 away from the analyzer into the horizontal plane (straight out). Align the SLX2
antenna parallel to the UA820 as close as possible. Move the unit along the UA820 antenna until
you find a maximum peak.
3. Do a peak search and measure the power to be at least 2 dBm for H5, J3, L4, and P4 bands and at
least 0 dBm for Q4, R5, JB, and S6 bands.
4. Set SPAN to 200 KHz. Measure the frequency to be within +/- 3 kHz of the nominal frequency you
are testing. (See frequency tables on pages 19 to 24).
TONE KEY LEVEL TEST
1. Set Power Supply to 3.0VDC
2. Find transmitting carrier on the spectrum analyzer with a span of 200 kHz. Use the "Peak Search,
Marker Delta, Next Peak" soft-keys on the analyzer.
3. Measure the 32.768 kHz tone key level to be -21 dBc ± 1.5 dB.
4. Set Power Supply to 2.1 V (1 segment on LCD battery icon).
5. Measure the 32.768 kHz tone key level to be -14 dBc ± 1.5 dB.
OCCUPIED BANDWIDTH TEST (JB model only)
1. Set transmitter gain to maximum.
2. Set up the HP-8591E spectrum analyzer to measure Occupied Bandwidth with the following set-
tings:
• Percentage Power = 99.5%
• Channel Spacing = 250 kHz
• Bandwidth = 110 kHz
3. Connect the audio generator to TQG connector CON90. Use a 1 kHz tone with a level that gives -
23.47 dBu (52mV) at TPA3.
4. Increase the audio level by 36dB.
5. Measure Occupied Bandwidth to be less than 110 kHz.
ADJACENT CHANNEL POWER TEST (JB model only)
1. Set the spectrum analyzer, and audio input level to the same settings as stated in “Radiated RF
Output Power and Frequency Stability” and “Distortion Test”.
2. Measure Extended Adjacent Channel Power to be less than -60 dB.
25A1090 (Rev.3)
IF ALL TEST PASSED, THIS MEAN S T H E UN IT IS P R OP ERL Y FU NCT IONING, AND
NO ALIGNMENT IS REQUIRED.
11
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