Sennheiser EM 100 G2 Service Manual download pdf (Page 7)

EM 100 G2, EM 300 G2, EM 500 G2

7 08/2004

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 ope-

rational 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.

1 2 3 4 5 6 7 8 9 10 11 12 ... 31 32

No comments

Sennheiser EM 100 G2 Service Manual Page 7