Sony WM-EX422 Service Manual

Product Overview

The Sony WM-EX422 is a portable cassette player. This document provides detailed service information.

Model Name Using Similar Mechanism: NEW

MD Mechanism Type: MF-WMFX495-147

Specifications

Design and specifications are subject to change without notice.

Battery life* (approximate hours):

* Measured value by the standard of JEITA (Japan Electronics and Information Technology Industries Association). (Using a Sony HF series cassette tape)

**When using a Sony LR6(SG) "STAMINA" alkaline dry battery (produced in Japan).

Note: The battery life may be shorter depending on the operating condition, the surrounding temperature and battery type.

Document Information: 9-877-095-02, 2003L02-1, ©2003.12

Publisher: Sony Corporation, Personal Audio Company, Published by Sony Engineering Corporation

Table of Contents

• Specifications
• 1. Servicing Note
• 2. General
• 3. Disassembly (Cabinet, Main Board, Mechanism Deck, Cassette Holder)
• 4. Adjustments (Mechanical, Electrical)
• 5. Diagrams (Block, Printed Wiring, Schematic, IC Block)
• 6. Exploded Views (Cabinet, Mechanism Deck)
• 7. Electrical Parts List

Flexible Circuit Board Repairing Notes: Keep soldering iron temperature around 270°C; avoid touching the same conductor multiple times; be careful with force during soldering/unsoldering.

Notes on chip component replacement: Never reuse disconnected chip components; be cautious with tantalum capacitors as they can be damaged by heat.

1. Servicing Notes

The unit uses a photo reflector (PH751) on the MAIN board to detect idler gear rotation. If the MAIN board is removed, the motor (M601) cannot be controlled. The MD switch (S601) is also on the MAIN board, affecting mechanism position detection. For voltage checks with the MAIN board removed, follow these steps:

1. Setting: Remove the MAIN board. Connect it to the motor (M601) using jumper wires (extension tool Part No. 1-769-143-11 recommended). Connect an AF oscillator to TP52 and BT401 (BATT-). Supply 1.5V to battery terminals via a regulated power supply.
2. Preset State: Ensure the slider (NRA) and MD switch (S601) are centered. If not, set the MD switch (S601) to match the slider (NRA) position. The slider (NRA) moves when the power supply switch is toggled OFF then ON; set the MD switch (S601) according to this timing to center position.
3. FF, REW Modes: Verify preset state. Input square or sine wave to TP52 and BT401 (BATT-). Press the [FF] or [REW] button.
4. PLAY Mode: Verify preset state. Input square wave to TP52 and BT401 (BATT-). Press the [PLAY] button (represented by a symbol like ▶️) once; move MD switch (S601) to align with slider (NRA) movement for FWD mode. Press [PLAY] again; move MD switch (S601) according to slider (NRA) movement for REV mode.

Note 1: If these steps fail, repeat from the preset stage.

Note 2: When using headphones, beep sounds can help time MD switch (S601) adjustments.

Diagrams:

• MAIN Board (Component Side): Shows PH751 (photo sensor) and S601 (MD CONT).
• MAIN Board (Conductor Side): Shows TP52, BT401 (battery terminal), AF oscillator connection for square wave (2 Hz, 2 Vp-p), and connection to motor (M601).

2. General

This section is extracted from the instruction manual and describes the player's controls:

• OPEN: Button to open the cassette compartment.
• HOLD: Button to lock controls.
• AVLS: Automatic Volume Limiter System button.
• MEGA BASS: Bass enhancement button.
• BATT: Battery compartment indicator.
• DIRECTION: Button to control tape direction (e.g., ▶️ for forward, ◀️ for reverse).
• VOL: Volume control knob (has a tactile dot for volume up direction).
• REW: Rewind button.
• FF: Fast Forward button.

Hand Strap Attachment: A point is indicated for attaching a hand strap (supplied with European models only).

Note: The button labeled 'VOL' has a tactile dot to indicate the direction for increasing volume. The button labeled 'DIRECTION' also has a tactile dot.

3. Disassembly

The equipment can be disassembled following these general steps:

Set -> Cabinet center -> MAIN board -> Mechanism deck -> Cassette holder sub assy -> Cabinet (front) sub assy.

Note: Follow the numerical order for disassembly.

3-1. Cabinet (Front) Sub Assy

The front cabinet assembly is removed by unscrewing screws and releasing claws.

• Step 1: Release cabinet center.
• Step 2: Remove Screw (B 1.7 x 9), tapping.
• Step 3: Remove Screw (B 1.7 x 9), tapping.
• The cabinet center has 6 claws. The front cabinet sub assy has 5 claws.

3-2. Main Board

The main board is accessed after removing the front cabinet. It involves unscrewing the board and disconnecting wires.

• Step 1: Unsolder HEAD flexible board.
• Step 2: Unsolder leads from the motor (four places).
• Step 3: Remove Screw (1.7 x 2.5), tapping.
• The main board is connected to the cabinet (center) assy.

3-3. Mechanism Deck

The mechanism deck is removed from the cabinet center assy.

• Step 1: Release claws.
• Step 2: Unsolder leads from motor (four places).
• Step 3: Remove Mechanism deck.
• The mechanism deck is connected to the cabinet (center) assy.

3-4. Cassette Holder Sub Assy

Installation of the cassette holder sub assy requires care with the spring (lid up) fitting into cabinet center holes. Removal involves pressing clips from the rear of the cabinet center.

• Use caution when installing the cassette holder assy with the spring (lid up) to fit into the holes on the cabinet center.
• Press on the left & right clips from the rear of the cabinet center and remove the boss.

4. Adjustments

4-1. Mechanical Adjustments

PRECAUTION:

• Clean playback head, capstan, pinch roller, and rubber belt with a denatured-alcohol-moistened swab.
• Demagnetize the playback head using a head demagnetizer. Do not use a magnetized screwdriver.
• Perform measurements and adjustments with the rated power supply voltage (1.5 V) unless specified otherwise.

Torque Measurement:

4-2. Electrical Adjustments

PRECAUTION:

• Supplied voltage: 1.5V.
• Switch and control position: MEGA BASS: NORMAL, VOLUME control (RV301): maximum, AVLS: OFF, HOLD: OFF, PB EQ: NORMAL.
• TAPE SECTION: 0 dB = 0.775V.

Tape Speed Adjustment:

• Test Tape: WS-48A (3kHz, 0dB).
• Procedure: Use a test tape (WS-48A). Set up a frequency counter connected to the headphone jack (J301).
• 1. Playback the tape in FWD state and adjust RV601 until the frequency counter reads 2,985Hz (Standard: 2,970-3,000Hz).
• 2. Playback the tape in REV state and check if the frequency counter reading is within ±1.5% of the FWD reading.

Adjustment Location: MAIN BOARD (SIDE B) - RV601: Tape speed adjustment.

5. Diagrams

5-1. Block Diagram

The block diagram illustrates the main functional blocks of the WM-EX422, including:

• System Control (IC701): Manages overall operations, including photo detection (PH751), battery control, key inputs, and motor control.
• Pre/Power Amp (IC301): Handles audio amplification, volume control (RV301), AVLS, and MEGA BASS functions, processing signals from the playback head (HP601).
• Motor Drive (IC601): Controls the capstan/reel motor (M601) for tape transport functions (PLAY, FF, REW) and speed regulation (RV601).
• Switches (S301-S303, S601, S701-S705): Control various functions like tape detection, AVLS, MEGA BASS, direction, hold, and mode selection.
• Power Supply: Includes battery input (BT401), voltage regulators (IC702, IC704), and switching regulation.

Signal paths are indicated by lines, with playback (PB) paths shown with a specific marker (Σ).

5-2. Printed Wiring Boards

The document shows the layout of the MAIN BOARD on Side A (component side) and Side B (conductor side). It details the placement of various components like ICs, transistors, resistors, capacitors, and switches, along with a semiconductor reference list indicating component locations.

5-3. Schematic Diagram

The schematic diagram provides a detailed circuit layout, showing interconnections between components such as ICs (TA2160FN, MM1279XVBE, ML63512-CFX1749, XC6371C251PL, PST9008, S-81211SG), transistors, resistors, capacitors, switches, the playback head (HP601), and the motor (M601). It details power supply lines (+2.5V, +1.3V, VBAT) and signal paths.

5-4. IC Block Diagrams

Detailed block diagrams are provided for key integrated circuits:

• IC301 TA2160FN (EL): Shows its internal functions for pre/power amplification, motor control, and various input/output signals.
• IC601 MM1279XVBE: Illustrates its role in capstan/reel motor drive, including speed control and start functions.

Notes on Schematic Diagram: Capacitors are in µF unless noted; resistors are in Ω. Power voltage is 1.5V DC. Voltages and waveforms are DC with respect to ground under no-signal conditions. VOM input impedance is 10 MΩ. Circled numbers refer to waveforms.

Notes on Printed Wiring Board: 'X' indicates parts from the component side; 'a' indicates through holes; ' ' indicates pattern from the side enabling seeing.

Waveforms:

• Waveform 1 (IC701 PHOTO CTRL): Shown as a square wave with approximately 1.0 Vp-p, measured with VOLT/DIV: 1V AC and TIME/DIV: 20msec.
• Waveform 2 (IC701 XT1): Shown as a sine wave at 32.768 kHz, approximately 1.3 Vp-p, measured with VOLT/DIV: 0.5V AC and TIME/DIV: 10 µsec.

6. Exploded Views

6-1. Cabinet Section

This section provides an exploded view of the cabinet assembly, listing part numbers and descriptions for components like knobs, screws, springs, levers, and the main PC board.

6-2. Mechanism Deck Section (MF-WMFX495-147)

This section provides an exploded view of the mechanism deck, listing part numbers and descriptions for components like pinch levers, wheels, belts, gears, springs, clutches, washers, and the motor.

7. Electrical Parts List

This section lists electrical components with their part numbers, descriptions, and specifications. It includes Capacitors, Diodes, Ferrite Beads, ICs, Jacks, Coils, Reflectors, Transistors, Resistors, Network Resistors, Variable Resistors, Switches, Thermistors, and Vibrators.

Revision History