AKG WMS 40 SINGLE/DUAL User manual

Page 1 of 24
WMS 40
Service Manual
*
11/07
Last modifications:
Parts canceled, no longer available
New part number pos. 15 page 6
Correction of part number's page 6
New part number pos.17 page 12
Part number for XL1, page 20
Designation of KR3 crystal corrected from 19115330 to 19115530
Page 22 connector: remark added
HT40: parts added
Page 20: CF1,3 part number corrected from 17001073 to 17201073
___________________________________________________________________________
AKG Acoustics GmbH, A Harman International Company, Lemböckgasse 21 - 25, A-1230 Wien Austria
Tel.: +(43 1) 86654 - 0; Fax.: +(43 1) 86654 - 1514; [email protected]

WMS 40
a Harman international company
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The complete WMS 40 system:
The actual frequency is not differentiated by item number!
WMS 40 HT/US – Set with US power supply: 7611X0001
WMS 40 HT/EU – Set with EU power supply: 7612X0001
WMS 40 HT/UK – Set with UK power supply: 7613X0001
WMS 40 PT/US – Set with US power supply: 7611X0002
WMS 40 PT/EU – Set with US power supply: 7612X0002
WMS 40 PT/UK – Set with US power supply: 7613X0002
WMS 40 PT/US/Aerobic – Set with C444 and US power supply: 7611X0003
WMS 40 PT/EU/Aerobic – Set with C444 and EU power supply: 7612X0003
HT 40, handheld transmitter only: 7600X0001
PT 40, bodypack transmitter only: 7600X0002
SR40/US, receiver only with US power supply: 7601X0003
SR40/EU, receiver only with EU power supply: 7602X0003
SR40/UK, receiver only with UK power supply: 7603X0003
General remarks
This manual contains technical information on the system functions and
design. Exploded views and lists of all available mechanic parts and electronic
assemblies are added. Further a list of electronic components for one specific
frequency for both handheld and bodypack transmitters and receiver is added
for better technical understanding and trouble shooting. However we do not
stock or sell electronic components contained in those electronic components
lists. When ordering frequency depending boards please state part number
plus required frequency.
All measurement values are nominal if not otherwise specified. All
data subject to change without prior notice . All rights reserved. The
contents of this manual shall be used for service purposes only. Any
use of the information given herewith by third parties without
permission of the copyright owner is strictly forbidden!
©2000 by AKG Acoustics GmbH, A Harman International Company,
A-1230 Wien, Austria.
Contacts:
e-mail: [email protected]

a Harman international company
a Harman international company WMS 40
Page 3 of 24
Short description Transmitter HT40:
Audio part:
The dynamic unit (D880) is connected via L1-L2-C6-C7 (RF-filter), to the MICAMP stage.
The MICAMP is built as an amplifier, which is a part of the NE575- integrated circuit and has
a gain of 8.8dB. It also forms the LOCUT
filter at 30 Hz. Then the signal is fed to the
COMPressor.
Here the dynamic of the amplitude is reduced to its half value, expressed in dB. This
compressor is built with the integrated circuit NE575 from Signetics. In the feedback loop of
the amplifier (Pin 12 and 14) there is the variable gain cell inserted. The variable gain cell
is controlled by the rectified output voltage of the amplifier. C60 smoothes the rectified
signal an controls the variable gain cell. C60 defines the so called time constant of the
compressor. This feedback loop leads in an compression of the input signal. R7-R8-C10
build the DC path in the feedback loop.
The second amplifier is used to build the PREEMphasis circuit, which boosts the higher
frequencies with an time constant of 50usec and a fixed gain of 7.9dB at the lower
frequencies.
The DEViation ADjustment is realized with the potentiometer R16. Here at an input level of
100mV/1kHz the deviation is adjusted to 15kHz, which is the nominal modulation. Also at
MUTE-position of the main switch, the signal is here shorted.
Q2 with the additional parts form the HICUT filter at app. 25 kHz/3rd order.
Via C29-R28-C30-R30 the signal modulates the CCO.
RF part:
The UHF Signal is generated by a crystal controlled oscillator CCO and multiplier amplifier
stages (AMP1, AMP2, AMP3, AMP4).
The third harmonic of the CCO is filtered by BPF1, after 3 doubler stages Ftransmit/2 is
filtered by BPF2. After the output amplifier AMP5 the signal is filtered by LPF and a ceramic
filter BPF3.
SETCode Transmitter Frequency Crystall Frequency Color
US54 710,400MHz 14,800MHz reddish brown
US58 734,600MHz 15,304MHz purple
EU62 802,525MHz 16,719MHz warm red
EU63 812,800MHz 16,933MHz yellow
UK69A 854,900MHz 17,810MHz violet
UK69B 858,200MHz 17,879MHz green
ISM1 863,100MHz 17,981MHz melon yellow
ISM2 864,375MHz 18,008MHz cool gray
SP1 848,750 MHz 17,6822 MHz skyblue
SP2 851,750 MHz 17,7447 MHz yellow green
KR3 745,650 MHz 15,5344 MHz mintgreen
KR4 750,900 MHz 15,6438 MHz dark grey
Power supply:
The internal voltage of 3.9V is generated from 2 AA size batteries with a DC/DC converter.

WMS 40
a Harman international company
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LPF
1
2
Order1
3.1KHz
2 wires
DC
DC
UBatt
3.9V
HT40-block schematics
Ftransmit/48
UHF-frequency rangeAF-frequency 40Hz ... 20KHz
Order3
23KHz
Order
2
40Hz
ON OFF
MUTE
MUTE OFF doubler doubler doubler doubler
Ftransmit/16 Ftransmit/2 Ftransmit
Ftransmit
XT2
CCO AMP1 AMP5 LPF
ANT
MIC COMP PREEMWIRE
DC/DC
LOWBATT
BATTERY
HICUTLOCUT
SWITCH
AMP3 AMP4AMP2MICAMP BPF1 BPF2 BPF3

WMS 40
a Harman international company
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3
4
1
8
2
5
6
7
9
16
12
17
13
10
11
15
14
18
16
19
Part nbr. :31404010
Attention: Before
reassembly twist
stranded wires
leading to capsule
in counter-
direction to the
way of screwing in
the threaded
sleeve. Otherwise
the wires will
break.
Achtung: Vor dem
Zusammenbau die
Litzen zur Kapsel
im Gegensinn zur
Schraubrichtung
der Gewindehülse
verdrillen, da sonst
die Anschlüsse
abreissen! 20

WMS 40
a Harman international company
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Short description Transmitter PT40:
Audio part:
The input signal is connected at Pin2 via L13L14C44C72 (RFfilter), to the MICAMP stage
(with Pin1 = ground). The supply voltage of 3.9V for the microphones is connected via R68
at pin 3 of the connector . For microphone application Pin2 and Pin3 has to be shorten in
the connector of the microphone. The MICAMP is built as an amplifier, which is a part of the
NE575 integrated circuit and has a variable gain of 0dB to 21dB. It also forms the LOCUT
filter at 30 Hz and the MIC/LINE switch is situated here, which reduces the input signal by
app. 14dB at line position.
Then the signal is fed to the COMPressor. Here the dynamic of the amplitude is reduced to
its half value, expressed in dB. This compressor is built with the integrated circuit NE575
from Signetics. In the feedback loop of the amplifier (Pin 12 and 14) is the variable gain
cell inserted. The variable gain cell is controlled by the rectified output voltage of the
Description Part number Item
Printed circuit main board, complete, tested 80004012 1
Printed circuit dc/dc board, complete, tested 80004013 2
ON/MUTE/OFF switch 92100400 3
Cr
y
stal 14.8003MHz
(
For US54
,
710.400MHz
)
reddish brown
19114801 4
Crystal 14.8128MHz (For US54B, 711,000MHz) skyblue 19114811 4
Crystal 15.3045MHz (For US58, 734.600MHz) purple 19115301 4
Crystal 15.354MHz (For US58B, 736.975MHz) yellowgreen 19115350 4
Crystal 15.602 MHz (For US60A, 748.875MHz) green 19115600 4
Crystal 15.6576MHz (For US60B, 751.550MHz) dark purple 19115650 4
Crystal 16.7196MHz (For EU62, 802.525MHz) warm red 19116710 4
Crystal 16.7732MHz (For EU62B, 805.100MHz) pink 19116772 4
Crystal 16.9336MHz (For EU63, 812.800MHz) yellow 19116930 4
Crystal 16.9399MHz (For EU63B, 813.100MHz) light red 19116931 4
Crystal 17.8107MHz (For UK69A, 854.900MHz) violetblue 19117810 4
Crystal 17.8795MHz (For UK69B, 858.200MHz) green 19117871 4
Crystal 17.9815MHz (For ISM1, 863.100MHz) melon yellow 19117980 4
Crystal 18.0081MHz (For ISM2, 864.375MHz) cool gray 19118000 4
Crystal 18.0180MHz (For ISM3, 864.850MHz) violet 19118011 4
Crystal 15.5344MHz (For KR3, 745.650MHz) mint green 19115530 4
Crystal 15.6438MHz (For KR4, 750.900MHz) dark gray 19115640 4
Crystal 17.6822MHz (For SP1, 848.750MHz) 19117680 4
Crystal 17.7447MHz (For SP2, 851.750MHz) 19117740 4
Crystal 16.846MHz (For JP1, 808.625MHz) greenbrown 19116840 4
Crystal 16.857MHz (For JP2, 809.125MHz) light blue 19116850 4
Ceramic Filter 710.151MHz (For US54) 19307100 20
Ceramic Filter 734.151MHz (For US58) 19307340 20
Ceramic Filter 747.141MHz (For KR3) 19374710 20
Ceramic Filter 750.141MHz (For KR4) 19307500 20
Ceramic Filter 802.151MHz (For EU62) 19308020 20
Ceramic Filter 812.151MHz (For EU63) 19308120 20
Ceramic Filter 854.151MHz (For UK69A) 19308540 20
Ceramic Filter 858.151MHz (For UK69B) 19308580 20
Ceramic Filter 864.152MHz (For ISM1) 19308640 20
Ceramic Filter 864.152MHz (For ISM2) 19308640 20
Ceramic filters for further frequencies on request 20
Battery compartment 24200010 5
Battery contact (helical spring) 36304010 6
Battery contact (plate) 36205150 7
Housing tube, printed 27004010 8
Antenna cover, black 21504010 9
Antenna cover, orange 21504013 9
Antenna cover, yellow 21504014 9
Antenna cover, red 21504012 9
Antenna cover, brown 21504011 9
Antenna cover, pink 21504017 9
Antenna cover, green 21504015 9
Antenna cover, violet 21504016 9
Antenna cover, grey 21504018 9
ON/MUTE/OFF label with LED lens 22004010 10
ON/MUTE/OFF slider 25204010 11
Frame for ON/MUTE/OFF slider 22204010 12
Battery door 20104040 13
Capsule 2610Z0034 14
Top grill 9999N07180 15
Housing screw 33002060 16
Rubber plate 65045140 17
Ring 36104010 18
Cover 30818090 19
Stand adapter 23200010 --

WMS 40
a Harman international company
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amplifier. C18 smoothes the rectified signal an controls the variable gain cell and is the so
called timeconstant of the compressor. This feedback loop leads in an compression of the
input signal. R45R46C24 build the dcpath in the feedback loop.
The second amplifier is used to build the preemphasis circuit, which boosts the higher
frequencies with an time constant of 50usec and a fixed gain of 7.9dB for the lower
frequencies.
The deviationadjustment is realized with the potentiometer VR3. Here at an inputlevel of
300mV at 1kHz (and the inputgain set to 0dB=minimumgain) the deviation is adjusted to
15kHz, which is the nominal modulation. Also at MUTEposition of the main switch, the
signal is here shorted.
Q7with the additional parts form the HICUTfilter at app. 25 kHz / 3. order.
Via C25R69C26R17 the signal modulates the CCO.
RF part:
The UHF Signal is generated by a crystal controlled oscillator CCO and multiplier amplifier
stages (AMP1, AMP2, AMP3, AMP4).
The third harmonic of the CCO is filtered by BPF1, after 3 doubler stages Ftransmit/2 is
filtered by BPF2. After the output amplifier AMP5 the signal is filtered by LPF and a ceramic
filter BPF3.
Power supply:
The internal voltage of 3.9V is generated from 2 AA size batteries with a DC/DC converter.

WMS 40
a Harman international company
Page 8 of 26
LPF
GC
1
2
Order1
3.1 KHz
3 Pins
DC
DC
UBatt
3.9V
-22...0dB
PT40-block schematics
Ftransmit/48
UHF-frequency rangeAF-frequency 40Hz ... 20KHz
Order3
23KHz
Order
2
40Hz
ON OFF
MUTE
MUTE OFF doubler doubler doubler doubler
Ftransmit/16 Ftransmit/2 Ftransmit
Ftransmit
0dB -14dB
XT2
CCO AMP1 AMP5 LPF
ANT
MIC
MICAMP
COMP PREEM
CON
DC/DC
LOWBATT
BATTERY
GAINPOT
HICUT
LOCUT
SWITCH
AMP3 AMP4AMP2
ATT
MIC/LINE
BPF1 BPF2 BPF3

WMS 40
a Harman international company
Page 9 of 26
Description Part number Item
Printed circuit board, complete, tested 80000402 1
Antenna 83200820 2
ON/MUTE/OFF switch 92100700 3
MIC/LINE switch 92100190 4
Sensitivity trimmer potentiometer 11001043 5
Crystal: see parts list for HT40, Pos 4 6
Housing, bottom shell 21600400 7
Housing, top shell, printed 20300400 8
Battery door 20100400 9
Battery contact (single helical spring) 36300400 10
Battery contact (plate) 36200400 11
Battery contact (plate with helical spring) 36003340 12
Belt clip 36400151 13
Housing screw 33026120 14
Mic socket 90605030 15
Ceramic Filter: see parts list for HT40, Pos 20 16
1
2
3
4 6 5
9
8
7
10
13
11
12
14
15
16

WMS 40
a Harman international company
Page 10 of 26
Short description Receiver SR40:
The SR40 is a stationary non diversity receiver applying a double conversion conception.
The receiver is non switchable, his reception frequency in the UHF range is:
SET CODE FRx: FLO1: XT1: FIF1: FLO2=XT2: FIF2:
US54 710,400MHz 654,400MHz
36,356MHz
56,0MHz
45,3MHz 10,7MHz
US58 734,600MHz 678,600MHz
37,700MHz
56,0MHz
45,3MHz 10,7MHz
EU62 802,525MHz 746,525MHz
41,474MHz
56,0MHz
45,3MHz 10,7MHz
EU63 812,800MHz 756,800MHz
42,044MHz
56,0MHz
45,3MHz 10,7MHz
UK69A 854,900MHz 798,900MHz
44,383MHz
56,0MHz
45,3MHz 10,7MHz
UK69B 858,200MHz 802,200MHz
44,567MHz
56,0MHz
45,3MHz 10,7MHz
ISM1 863,100MHz 807,100MHz
44,839MHz
56,0MHz
45,3MHz 10,7MHz
ISM2 864,375MHz 808,375MHz
44,910MHz
56,0MHz
45,3MHz 10,7MHz
The elements determining the reception frequency are the band pass filter BPF1 and the
crystal of local mixer oscillator XT1
RFPart:
The front end consists of a ceramic pass band filter BPF1, a bipolar transistor amplifier
AMP1 and a low pass filter LPF. The 1st MIXER1 converts the RF signal to the 1st
intermediate frequency of 56MHz, the 2nd MIXER2 converts the signal to the 2nd
intermediate (demodulation) frequency 10.7MHz.
The 2nd intermediate frequency is band pass filtered (BPF2,3), amplified (AMP2) and gets to
the input of the demodulator IC (LIMAMP and DEMOD).
The 1st mixer oscillator (CCO1) is designed as a crystal controlled oscillator (the 3rd
harmonic is filtered out by BPF4) and multiplier amplifiers AMP3 and AMP4. The LO signal is
filtered by BPF5, BPF6 and is 56MHz below the reception frequency.
The 2nd mixer oscillator (CCO2) is crystal controlled too, his frequency is 45,3MHz.
AudioPart:
The audio signal from DEMODulator (BA4110IFdemodulator) is amplified by AFAMP with
U11Pin123. Here the output signal is adjusted to 500mV/1kHz at 15kHz deviation.
Then the signal runs to the MUTEstage, which is the second half of U11. Muting is realized
with Q29, which shortens the feedback path. Q29 is controlled by the RSSI signal.
The RSSIsignal comes from the IFcircuit BA4110. U7 forms an COMPARATOR, which
switches the MUTEtransistor Q29 at RSSIlevel lower than 98dBm. This value can be
adjusted via SQUELCHpotentiometer VR1.
Q25 builds an HICUTfilter at 20 kHz/2nd order. Amplifier Pin17/18/19 of NE575 forms the
DEEMphasis circuit. The frequencies above 3 kHz are decreased with first order
(timeconstant 50 µsec).
Then the signal is expanded with the EXPander circuit NE575. Here the original level
behavior of the input signal at the transmitter input is restored. The expander time
constant is defined by C48.
The second free amplifier of NE575 is used as buffer before the volume control section.
With VR2 (VOLUME) the output level can be adjusted from line level (500mV) to mic. level
(35mV). The next stage is a amplifier with a gain of 3.9dB OUTAMP.
C39 separates the dcvoltage from the signal and then the signal is fed to the XLR and
6.3mm JACK. Q31 and Q32 build a CLICKSUPPRessioncircuit. In the OFFposition of the
main switch this transistors are turned on. If the receiver is turned ON, the transistors
remain ON for a short time (by C50), so the clicksignals caused by the amplifiers is
suppressed.
The balanced output has symmetrical impedance, which is built by R84/R87 and R88/R89.
The receiver is powered by an external device which is to be connected at the rear panel (DC
jack POWER) and can be turned on and off by a switch at the front panel (ON/OFF). The
internal used voltage (+8V) is stabilized by the DC circuitry (VREG).