Audio tuner control unit, component description - GF82.62-P-3132SXS

MODEL 216.3, 221.0/1 with CODE (494) USA version up to Model Year 8

MODEL 216.3, 221.0/1 with CODE (498) Japan version up to Model Year 8

MODEL 216.3, 221.0/1 with CODE (810) Sound system up to Model Year 8

Illustrated on model 221

Fig 1: Identifying Audio Tuner Control Unit - Illustrated On Model 221

Courtesy of MERCEDES-BENZ USA

Location

The audio tuner control unit is located on a bracket in the luggage compartment on the left side wall behind the paneling.

Task

The audio tuner control unit is the radio component and simultaneously the sound version of the audio system and is connected to the Media Oriented System Transport (MOST). 2 radio receivers are integrated in the audio tuner control unit, which ensure the reception of the country-specific radio stations. The audio tuner control unit administers all audio sources integrated in the vehicle (e.g. radio tuner, DVD changer) and processes their audio signals.

Design

The following components and interfaces are integrated in the audio tuner control unit:

2 radio receivers for reception of radio signals
MPEG decoder for processing of audio signals in DVD mode (audio or video DVD)
Integrated sound amplifier
MOST interface

Function

The audio tuner control unit receives, depending upon the national version, high frequency (HF) signals for different frequency ranges (e.g. ultra-short wave (FM), medium wave (MW)). These HF signals are sent to the audio tuner control unit via a HF line directly from the rear window antenna amplifier module (A2/12). There, the incoming signals are processed, amplified and output via the speaker system.

Moreover, dynamic volume adjustment is possible in combination with the audio tuner control unit. During dynamic volume adjustment, the noise level in the vehicle is measured via a separate microphone, the sound amplifier microphone (B25/6). The measured value is used to dynamically adjust the volume level to the background noise in the vehicle. The microphone signals are read in discretely in several steps.

Diagnosis

The audio tuner control unit has its own fault memory. All faults that have occurred during operation are stored there in a non-volatile memory.

In the event of a request via STAR DIAGNOSIS, all diagnostic data are forwarded via the MOST to the COMAND controller unit (A40/3) which serves as the interface to the central CAN.

The requested diagnostic data are then forwarded to the central gateway control unit (N93) via the central CAN where they can be read out at the data link connector (X11/4).