AKG WMS 40 Service Manual

Revision: 11/07

System Overview

The AKG WMS 40 system is a wireless microphone system available in various configurations, including handheld (HT40) and bodypack (PT40) transmitters, and a stationary receiver (SR40). The system operates in the UHF band and offers different frequency sets for various regions.

WMS 40 System Configurations

HT/US Sets: US power supply (7611X0001)
HT/EU Sets: EU power supply (7612X0001)
HT/UK Sets: UK power supply (7613X0001)
PT/US Sets: US power supply (7611X0002)
PT/EU Sets: US power supply (7612X0002)
PT/UK Sets: US power supply (7613X0002)
PT/US/Aerobic Sets: With C444 and US power supply (7611X0003)
PT/EU/Aerobic Sets: With C444 and EU power supply (7612X0003)
HT 40 Transmitter only: (7600X0001)
PT 40 Transmitter only: (7600X0002)
SR40/US Receiver only: US power supply (7601X0003)
SR40/EU Receiver only: EU power supply (7602X0003)
SR40/UK Receiver only: UK power supply (7603X0003)

General Remarks

This manual provides technical information on system functions and design, including exploded views and parts lists. It also includes a list of electronic components for specific frequencies. AKG Acoustics GmbH does not stock or sell individual electronic components listed in this manual. All measurement values are nominal and subject to change without prior notice. The contents of this manual are for service purposes only.

Transmitter HT40 - Audio Part Description

The audio signal from the dynamic unit (D880) is processed through an amplifier (MICAMP), a compressor, and a pre-emphasis circuit. The deviation adjustment is controlled by a potentiometer, and a HICUT filter is implemented. The signal then modulates the CCO (Crystal Controlled Oscillator).

Transmitter HT40 - RF Part Description

The UHF signal is generated by a CCO and multiplier amplifier stages. Filters (BPF1, BPF2, LPF, BPF3) are used to shape the signal before it is transmitted.

Transmitter HT40 - Power Supply

The transmitter is powered by 2 AA batteries, with an internal voltage of 3.9V generated by a DC/DC converter.

Transmitter HT40 - Exploded View and Parts List

The manual includes an exploded view of the HT40 transmitter with numbered components and a corresponding parts list detailing descriptions, part numbers, and item references. Key components include the capsule, housing, switches, and various electronic parts.

Transmitter PT40 - Audio Part Description

The PT40 transmitter's audio signal is processed similarly to the HT40, involving an amplifier (MICAMP), compressor, and pre-emphasis circuit. It also features a deviation adjustment and a HICUT filter.

Transmitter PT40 - RF Part Description

The RF section of the PT40 utilizes a CCO and multiplier amplifier stages, with filtering stages (BPF1, BPF2, LPF, BPF3) to condition the UHF signal.

Transmitter PT40 - Power Supply

Power is supplied by 2 AA batteries, with a DC/DC converter providing the internal 3.9V.

Transmitter PT40 - Exploded View and Parts List

An exploded view and parts list are provided for the PT40 transmitter, detailing components such as the printed circuit board, antenna, switches, housing, battery contacts, and various electronic components.

Receiver SR40 - Description

The SR40 is a stationary non-diversity receiver with a double conversion design. It operates within the UHF frequency range and is not switchable.

Receiver SR40 - RF Part Description

The receiver's front end includes a ceramic pass band filter (BPF1), amplifier (AMP1), and low-pass filter (LPF). It uses two mixers (MIXER1 and MIXER2) to convert the RF signal to intermediate frequencies of 56MHz and 10.7MHz, respectively. Local oscillators (CCO1 and CCO2) are crystal-controlled.

Receiver SR40 - Audio Part Description

The audio signal is amplified by an AFAMP, processed through a mute stage controlled by the RSSI signal, and then passes through a HICUT filter and a de-emphasis circuit. An expander circuit restores the original signal level, followed by volume control and an output amplifier. A click suppression circuit is included to minimize noise during power transitions.

Receiver SR40 - Power Supply

The receiver is powered by an external 12V DC power supply connected via a rear panel DC jack.

Receiver SR40 - Block Schematics

Block diagrams illustrate the internal signal flow for both the transmitter (HT40/PT40) and receiver (SR40), showing the arrangement of audio frequency (AF) and UHF frequency components, including filters, amplifiers, mixers, oscillators, and control circuits.

Receiver SR40 - Exploded View and Parts List

An exploded view and detailed parts list are provided for the SR40 receiver, identifying components such as the tuner, main board, antenna, power switch, volume potentiometer, LEDs, sockets, housing parts, and screws.

Parts Lists (Resistors, Capacitors, etc.)

Extensive parts lists are included, detailing specific resistor (R), capacitor (C), inductor (L), transistor (T, Q), diode (D), integrated circuit (U), switch (SW), and crystal (XT) components used in the WMS40 system, often specifying their values, tolerances, and part numbers. These lists are organized by component type and sometimes by frequency or model.

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