The Kenwood DP-M87 is a compact disc player, designed to be integrated into a larger audio system, as indicated by its compatibility with various Kenwood amplifier, tuner, cassette deck, graphic equalizer, and speaker models (e.g., K-77M, K-88M, K-99M, MIDI M-57M, MIDI M-77M, MIDI M-97M). It features a multi-disc magazine system, allowing for continuous playback of multiple CDs.
Function Description:
At its core, the DP-M87 functions as a digital audio compact disc player. It utilizes a semiconductor laser to read digital audio data from compact discs. The player incorporates a 1-bit D/A converter with 8fs (352.8kHz) oversampling for digital-to-analog conversion, aiming for high fidelity audio output. The mechanism supports a variable playing rotation speed from 200rpm to 500rpm (CLV - Constant Linear Velocity).
The internal circuitry includes a Microprocessor (SC75217GF-642), a Servo IC (CXA1782BQ), and a Digital Signal Processor (CXD2517Q). These components manage disc loading, playback, error correction, and overall system control. The microprocessor handles user input, display functions, and communication with other system components. The servo IC controls the laser pickup's focusing, tracking, and feed mechanisms, ensuring accurate data retrieval from the disc. The digital signal processor is responsible for EFM demodulation, error correction, and generating the digital audio stream for the D/A converter.
The player supports various control inputs, including disc selection (DISC 1-6, DISC P), playback controls (PLAY, STOP, FF, FB, REPEAT, RANDOM, SPACE), and utility functions (UP, DOWN, EDIT, TIME). It also features a multi-disc magazine system, allowing for sequential loading and playback of up to six discs.
Important Technical Specifications:
- System: Compact disc digital audio system
- Laser: Semiconductor laser
- Number of channels: 2 channels
- Playing rotation: 200rpm ~ 500rpm (CLV)
- D/A conversion: 1 Bit, 8fs (352.8kHz) oversampling
- Dynamic range: More than 90dB
- Total harmonic distortion: Less than 0.005%
- Channel separation: More than 90dB
- Wow & Flutter: Unmeasurable limit
- Output level/impedance (Fixed): 1.2V / 1kΩ
- Frequency response: 20Hz ~ 20kHz, ±1.0dB
- Signal to noise ratio: More than 96dB
- Dimensions (W x H x D): 360mm x 90mm x 353mm
- Weight (net): 4.1kg
Usage Features:
The DP-M87 is designed for ease of use within a Kenwood audio system. It comes with several accessories to facilitate its integration and operation:
- Magazine: A multi-disc magazine (J19-3394-13) is packed with the CD player, allowing users to load multiple CDs for continuous playback.
- Antennas: FM indoor antenna (T90-0175-05) and AM loop antenna (T90-0174-05) with a stand (J19-2815-04) are included, suggesting potential integration with a tuner component. An antenna adaptor (T90-0185-05) for 75Ω/300Ω T,E type is also provided.
- Cables: Audio cords (E30-0505-05, E30-0615-05) and system control cords (E30-2627-05, E30-2628-05) are supplied for connecting the player to other audio components.
- Power Adaptor: An AC plug adaptor (E03-0115-05) of M type is included for units with a European AC plug in areas other than Europe.
- Remote Control: A remote control unit (X94-1011-41 or X94-1050-11) is provided, along with AAA/R03 batteries and a battery cover (A09-0126-03 or F07-0721-23), enabling convenient operation from a distance.
- Display: The front panel features a fluorescent display that shows disc number, track number, and various playback statuses (e.g., REPEAT, RANDOM, PGM, SPACE, TIME).
- Controls: Front panel buttons allow for direct control of disc loading, playback, and other functions. The "EDIT" key, for example, opens the door and ejects the P1 tray.
Maintenance Features:
The service manual provides detailed information for maintenance and repair, indicating a design that supports serviceability:
- Test Mode: The unit includes a "TEST MODE" accessible by short-circuiting specific test pins (#2 and #3) on the microprocessor. This mode allows technicians to check various servo functions (focusing, tracking, feed), laser operation, and display functions. Different input keys (STOP, REPEAT, RANDOM, TIME, PLAY, DISC 1, DISC 2) trigger specific diagnostic displays and actions within this mode.
- Circuit Descriptions: Detailed circuit diagrams and pin function descriptions for the main ICs (Microprocessor SC75217GF-642, Servo IC CXA1782BQ, Digital Signal Processor CXD2517Q) are provided, aiding in troubleshooting and component-level repair.
- Adjustment Procedures: The manual outlines specific adjustment procedures for "Tracking Error Balance," "Focus Error Balance," "Focus Gain," and "Tracking Gain." These adjustments, performed using test discs (e.g., SONY YEDS-18 TEST DISC) and oscilloscopes/VTVMs, are crucial for maintaining optimal playback performance. The procedures involve connecting test equipment to specific points (e.g., CN3 pins for RF and TE signals) and adjusting potentiometers (VR1, VR2, VR3, VR4) to achieve desired waveforms and voltage readings.
- Exploded Views and Parts List: Exploded views of the unit and mechanism (both Japan-made and Singapore-made versions) are included, along with comprehensive parts lists. These resources are invaluable for identifying and ordering replacement parts.
- Safety Precautions: The manual emphasizes safety during maintenance, particularly regarding laser radiation ("DANGER: Laser radiation when open and interlock defeated. AVOID DIRECT EXPOSURE TO BEAM.") and electrical safety ("CAUTION: For continued safety, replace safety critical components only with manufacturer's recommended parts (refer to parts list). Indicate safety critical parts/components. To reduce the risk of electric shock, leakage current or resistance measurements shall be carried out (exposed parts are acceptably insulated from the supply ground) before the appliance is returned to the customer."). It also advises using a specific power supply jig (RM-90PS) or an A-848's power transformer for 9V AC supply during repair, rather than a "RHEOSTAT."
- Serial Number Information: The service manual specifies that it covers changing information from serial No. 31240001 onwards, indicating ongoing support and updates for the product line. It also refers to the DP-MA5/MA9 service manual for more detailed descriptions, suggesting commonality in design and service procedures across related models.
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