Sennheiser EM 500 G2, EM 300 G2, EM 100 G2 Service Manual

Service manual

EM 100 G2 EM 300 G2 EM 500 G2

SA 040818

SET

POWER

300

EM 100 G2

SET

EM 300 G2

500

SET

Short Description

The three stationary receivers EM 100 G2, EM 300 G2 and EM 500 G2

,True Diversity’ receivers and are equipped with the HDX noise reduction

are system. Each receiver has a switching bandwidth of 36MHz in the UHF band.

EM 500 G2

Features

• 1440 UHF frequencies available for interference-free reception.

• Direct channel selection via presets.

• Scan function for finding free receive channels.

• Low battery warning on transmitter and receiver.

• Squelch pilot tone for interference-free operation.

• Sound check mode for checking transmission conditions

(only EM 500 G2).

Subject to alterations

Sennheiser electronic GmbH & Co. KG • 30900 Wedemark Phone: +49 (5130) 600 0 • Fax: +49 (5130) 600 300 1/32

Safety requirements

Observe safety regulations.

Observe ESD instructions while handling electrostatically endangered components.

Only skilled persons are allowed to alter and repair. For repairs and exchanges only approved components according to the current spare parts list are allowed.

It is forbidden to alter the product unauthorised. If not observed the adaptor is legally liable for possible results of damage.

repairs/exchanges The following instructions for overhaul and testing must be followed. In case of

unusual problems please contact your Sennheiser distributor.

EM 500 G2, EM 300 G2, EM 100 G2

2/32 08/2004

Table of contents

1 Controls and indicators .................................................................................4

2 Technical data................................................................................................. 5

2.1 General.................................................................................................................... 5

2.2 RF part..................................................................................................................... 5

2.3 AF part .................................................................................................................... 6

3 Description ...................................................................................................... 7

3.1 Mainboard .............................................................................................................. 7

3.2 RF module............................................................................................................... 8

3.3 Display module...................................................................................................... 9

3.4 Monitor module (only EM 500 G2).................................................................... 9

4 Exploded view...............................................................................................10

4.1 Exploded view: EM 100 G2................................................................................ 10

4.2 Exploded view: EM 300 G2, EM 500 G2 .......................................................... 11

5 Test and alignment instructions................................................................ 13

5.1 Measuring and test equipment .......................................................................13

5.2 Measuring set-up................................................................................................13

5.3 Test table..............................................................................................................14

5.4 Reading out/changing unit data via the “DATA“ service interface .........17

6 Circuit diagrams ...........................................................................................19

Block diagram ...................................................................................................................19

Mainboard, circuit diagram, part 1/3...........................................................................20

Mainboard, circuit diagram, part 2/3...........................................................................21

Mainboard, circuit diagram, part 3/3...........................................................................22

RF board, circuit diagram, part 1/3..............................................................................23

RF board, circuit diagram, part 2/3..............................................................................24

RF board, circuit diagram, part 3/3..............................................................................25

Monitoring module MOD.A020, circuit diagram........................................................26

Interconnector assignmet ..............................................................................................27

Mainboard, component side ..........................................................................................28

Mainboard, solder side....................................................................................................29

RF board, component side..............................................................................................30

RF board, solder side .......................................................................................................31

Monitoring module: MOD.A020, component side .....................................................32

Monitoring module: MOD.A020, solder side...............................................................32

EM 500 G2, EM 300 G2, EM 100 G2

3/32 08/2004

1 Controls and indicators







Front

쐃 Headphone output, ¼

(only EM 500 G2)



SET

DATA

쐅쐈 쐉 씈 씉

(6.3mm) jack socket (PHONES)

쐇 Headphone volume control (VOL)

(only EM 500 G2)

쐋 Display 쐏 Button  / 

(two separate buttons on EM 100 G2)

쐄 Button SET 쐂 Button ON / POWER

Back panel

쐆 Cable grip for mains unit connector cable 쐊 DC socket for power supply unit connection (DC IN) 쐎 XLR socket for AF output (AF OUT BAL) 쐅 Audio output jack socket (AF OUT UNBAL) 쐈 RJ45 socket as service interface (DATA) 쐉 BNC socket as antenna input 2 (ANT II) 씈 Type plate 씉 BNC socket, antenna input 1 (ANT I)

EM 100 G2, EM 300 G2, EM 500 G2 08/2004 4/32

2 Technical data

2.1 General

Nominal output ______________________ +12V Operating voltage ____________________ +10.5 ... +16V Current consumption at nominal voltage ___ typ. 200mA Quiescent current consumption (standby) __ typ. 50mA Temperature range ___________________ -10°C ... +55°C Dimensions (in mm)___________________ 212 x 145 x 38 Weight: ____________________________ approx. 1200g Approval ___________________________ D801 488L RF Max. audio output level (balanced/unbalanced)

3-pin XLR socket_________________ +19dBu

1/4 " (6.3 mm) jack socket_________ +13dBu Headphone output (only EM 500 G2) THD (at nominal deviation, 1 kHz) Control range (only EM 500 G2) _________ 40dB

_____¼

__________ ≤ 0.9%

(6.3 mm) jack socket, stereo

2.2 RF part

Receiver principle _____________________ true diversity Frequency ranges_____________________ 518 – 554MHz

626 – 662MHz 740 – 776MHz 786 – 822MHz

830 – 866MHz Switching bandwidth __________________ 36MHz Receive frequencies ___________________ 1440 Channel separation ___________________ > 400kHz Channel grid_________________________ 25kHz

1. Oscillator frequency _________________ f

1. Intermediate frequency ______________ 241MHz

2. Oscillator frequency _________________ 230.3MHz

2. Intermediate frequency ______________ 10.7MHz Modulation__________________________ wideband FM Nominal/peak deviation________________ ±24kHz / ±48kHz Frequency stability Adjacent channel selection

EM 100 G2 _____________________ EM 300 G2 EM 500 G2

Intermodulation attenuation

EM 100 G2 _____________________ EM 300 G2 EM 500 G2

________________________ ≤ ±15ppm

__________________________ ≥ 68dB __________________________ ≥ 70dB

= fe + 241MHz

Osc

≥ 65dB

EM 100 G2, EM 300 G2, EM 500 G2

5 08/2004

Blocking

EM 100 G2, EM 300 G2 EM 500 G2

Squelch _____________________________off, low: 5dBµV,

Squelch pilot tone _____________________adjustable S/N = 52 dBA (unweighted with HDX) _____< 2.5µV (typ. 1.4µV) S/N = 80 dB (unweighted with HDX) _______< 10µV (typ. 6µV) S/N max (peak deviation with HDX) _______> 120dB(A) (typ. 124dB(A) Antenna inputs ______________________RF input: 2 BNC sockets, 50

_________________________ ≥ 75dB

______________ ≥ 70dB

mid: 15dBµV high: 25dBµV

2.3 AF part

Compander system ____________________HDX S/N (AF OUT)

EM 100 G2 EM 300 G2 EM 500 G2

AF output voltage (nominal deviation)

Unbalanced _____________________1.25V = +4dBu Balanced _______________________2.45V = +10dBu

AF output voltage (peak deviation)

Unbalanced 3.4V = +13dBu

Balanced 6.8V = +19dBu AF frequency response _________________50Hz ... 18kHz; -3dB Monitor output level/load _______________> 100mW/32 AF outputs ______________________¼" (6.3mm) jack socket

Pilot tone

Pilot tone frequency ______________32.768kHz

Pilot tone deviation _______________

_____________________ ≥ 110dB(A) _____________________ ≥ 112dB(A) _____________________ ≥ 115dB(A)

Ω (only EM 500 G2)

Unbalanced XLR-3M, balanced

≥ 1.5kHz

Ω

EM 100 G2, EM 300 G2, EM 500 G2 08/2004 6/32

3 Description

The receiver has a modular structure and comprises the following boards:

• Mainboard

• Display module

• RF module

• Monitor module (only EM 500 G2)

The display, RF and monitor modules are each connected to the mainboard via a 15-pin ribbon connection. The following sections explain the principal functions.

3.1 Mainboard

The mainboard is a single-sided PCB assembly. It is manually screwed to the side walls, the front and the back panel wall and the RF module. The mainboard performs the following functions:

• Conditioning of power supply

• Conditioning of AF signals

• Provision of power supply to additional modules

• Control of own functions and the RF and monitor module via the

microprocessor

3.1.1 Processing the diversity signal

The signal from the RF module with the highest field strength is switched by the U50 or U51 diversity switches and reaches four signal conditioning blocks that are connected in parallel.

3.1.2 U52 squelch switch with AF conditioning

If the squelch threshold you set is exceeded, U1 uses U52 to switch the AF signal and activates the AF high pass filter with U75-1, the AF low pass filter with U75-2 and U76-1, the HDX expander with U100 and the AF stages U101-1, U101-2 and U76-2.

With EM 500 G2 the AF stages U101-1 and U101-2 are used via analog switch U300 as LOW-CUT filters with a threshold frequency of 200Hz and with U301 as HI-BOOST filters with an increase of approx. 5dB at 10kHz. Control is via U1, Q300-1 and Q300-2.

The peak detector is connected to the level indicator behind U76-1 with U100 operational amplifiers (U100-2 and U100-1) whose output signal DEV_L is available to microprocessor U1 for evaluation.

The two AF signals AF_0 (U76-2) and AF_180 (U101-2) both reach a divider resistance chain at the inputs of analog switches U175 and U176, via which eight AF signal switching stages are set by the user. The structure is strictly balanced and is laid behind the active stages to guarantee full signal to noise ratio even if the AF signal is weakened by approx. 40dB. From the two outputs, the AF signal then reaches across various components to protect from ESD parasitic signals and phantom voltage at AF sockets P175 and J175.

EM 100 G2, EM 300 G2, EM 500 G2

7 08/2004

3.1.3 Evaluation of the TX battery signal

The battery telegram sent by the transmitter reaches the U60-2 trigger stage, at whose output appropriate square wave signals are available for evaluation by U1, via the 4Hz low pass filter with U60-1.

3.1.4 Evaluation of the pilot signal

The 32.768kHz pilot signal sent by the transmitter is filtered from the signal mix by the active crystal filter with Q95, Y95 and U95-1, rectified via the D95 diode and made available for evaluation by U1 via trigger stage U96-1.

3.1.5 Functions of microprocessor U1

The receiver is controlled by the 8-bit U1 microprocessor, which contains in its flash memory the control program and uses a sub-area as an EEPROM for saving data even in the event of power failure. The microprocessor uses a 4MHz crystal to generate both its own internal 8MHz cycle and the reference frequency for the RF module PLL. It processes the signals already described in line with the program specifications and the user specifications that can be set on an individual basis via a menu.

3.1.6 Service interface (RJ45 socket)

The service interface “DATA“ with RS485 protocol, located on the back panel of the unit, fulfills an important function. The RJ45 socket allows the relevant EEPROM parameters on the RF module and the simulated EEPROM to be read out and modified in the microprocessor. This interface also enables a software update as part of the hardware options. For example, the RJ45 socket enables you to read unit data and write-in after replacing a board. The necessary service software is available for download free of charge on our Internet homepage:

www.sennheiser.com > Service & Distributors > Service Documentation > Download

3.2 RF module

The RF module is a single-sided PCB assembly that is fixed to the back panel via the BNC input sockets and to the mainboard via a sheet metal brace. The RF module performs RF conditioning until demodulation of the IF signal. The module is connected to the mainboard via a 15-pin ribbon connection; the following functions are performed by the plug-in connection:

• Incoming power supply of 5V DC from the mainboard.

• Incoming system cycle (4MHz) from mainboard microprocessor.

• 2 x outgoing AF voltage to mainboard

• 2 x RSSI voltage to mainboard.

• Communication between the mainboard microprocessor and

the EEPROM or the PLL for the RF module.

EM 100 G2, EM 300 G2, EM 500 G2 08/2004 8/32

3.2.1 RF module shielded compartments

The shielded compartments on the RF module perform the following functions:

• The two compartments between the BNC sockets contain the second mixer,

the 10.7MHz limiting amplifier and the FM demodulator.

• The compartment directly behind the BNC socket contains RF conditioning

up to an including the SAW filter for the first IF.

• The middle compartment performs frequency conditioning for the first

oscillator with VCO, buffer and PLL for both diversity channels.

The input filters are assembled outside the shielded compartments to ensure that parasitic LO frequency currents cannot be coupled directly to the RF input. The input filters are relatively complex owing to the integrated IF and LO cases, but nevertheless do not require alignment.

3.2.2 Alignment of the RF module

The only components still to be adjusted are

• C540 for alignment of VCO voltage at center frequency,

• C330 for setting the LO2 crystal oscillator,

• The L310 and L410 discriminator coils, and

• The two level adjusters for the AF outputs.

For communication with the processor on the mainboard, the RF module contains the U700 EEPROM, in which the relevant frequency range data, the RSSI table and other status data are stored. Communication is processed via the same bus used by the microprocessor to communicate with the PLL U500 (frequency setting).

3.3 Display module

The display module for the status displays is connected to the mainboard via a 15-pin ribbon connection.

3.4 Monitor module (only EM 500 G2)

The monitor module (MOD.A020) is a single-sided PCB assembly and is connected to the mainboard via a 15-pin plug-in connector. The monitor module PCB has a jack socket for connecting headphones, and an appropriate volume control. The monitor module also has a complete U1 and U2 amplifier for each AF phase; the volume can be adjusted via R1.

The monitor module is primarily intended for stereo operation, but in phase configuration is possible for mono operation. If you want to minimize the volume differences in mono operation between the left and right channel (this may occur as a result of the tolerances of R1), you must close the M1 solder bridge.

You must not close the M1 solder bridge if you are using the monitor module in stereo mode.

EM 100 G2, EM 300 G2, EM 500 G2

9 08/2004

4 Exploded view

4.1 Exploded view: EM 100 G2

003

007

006

incl.:

Pos. 006

017

018

013

017

018

002

001

020

008

013

016

012

019

011

009

003

005

004

002

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+ 22 hidden pages