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LIFESTYLE® MODEL 20 MUSIC CENTER (CD-20)

©

1999 Bose Corporation

Service Manual
Part Number 183884 REV. 02

Last updated 9/20/00 Includes S4, S5, S6, S8, and S9
Updated page 46 on 02/06/2001 Updated page 46, U2 on 9/19/01

Contents

Safety Information ............................................................................................................................ 2 Electrostatic Discharge Sensitive (ESDS) Device Handling ........................................................ 3 CD-20 Manual Revision Overview .................................................................................................. 3 Specifications ................................................................................................................................ 4-7 Theory of Operation .................................................................................................................... 8-13 Figure 1. CD-20 Block Diagram ..................................................................................................... 13 Disassembly/Assembly Procedures ....................................................................................... 14-15 Figure 2. Disassembly/Assembly View .......................................................................................... 16 Figure 3. Exploded View of Door ................................................................................................... 17 RC-20 Remote Disassembly/Assembly........................................................................................ 18 Figure 4. RC-20 Disassembly/Assembly View ............................................................................... 18 CD Mechanism Disassembly Procedures ............................................................................... 19-23 Test Procedures ........................................................................................................................ 24-28 Figure 5. Tuner Alignment Locations .............................................................................................. 28 Remote Control Alignment ............................................................................................................ 29 Figure 6. RC-20 Tuning Locations ................................................................................................. 29 Alignment Procedures .............................................................................................................. 30-31 Part List Notes ................................................................................................................................ 32 Main Part List .................................................................................................................................. 33 Figure 7. CD-20 Exploded View ..................................................................................................... 34 CD Mechanism Part List ................................................................................................................ 35 Figure 8. CD Mechanism Exploded View ....................................................................................... 36 Electrical Part List ..................................................................................................................... 37-48 Figure 9. RC-20 Remote Exploded View ....................................................................................... 48 RC-20 Remote Part List ................................................................................................................. 49 RC-20 Remote Electrical Part List ........................................................................................... 49-50 Packaging Part List ........................................................................................................................ 51 Figure 10. Packaging Exploded View ............................................................................................ 51 Accessory Part List ........................................................................................................................ 52 Figure 11. Accessory Packaging ................................................................................................... 52 IC Block Diagrams and Pinouts ............................................................................................... 53-55 CD Mechanism IC Block Diagrams .......................................................................................... 56-59 CD Mechanism IC Pin Configuration Tables .......................................................................... 60-66 CD Mechanism IC and Transistor Voltage Tables .................................................................. 67-68 CD Mechanism Troubleshooting ............................................................................................. 69-86 CD-20 Troubleshooting Waveforms ........................................................................................ 87-91

REV01-02 CHANGED MAGAZINE PART NUMBER

CAUTION: THE BOSE® MODEL 20 (CD-20) MUSIC CENTER CONTAINS NO USER-SERVICEABLE PARTS. TO PREVENT WARRANTY INFRACTIONS, REFER SERVICE TO WARRANTY SERVICE STATIONS OR FACTORY SERVICE.

1

SAFETY INFORMATION
1. Parts that have special safety characteristics are identified by the symbol on schematics or by special notes on the parts list. Use only replacement parts that have critical characteristics recommended by the manufacturer. 2. Make leakage current or resistance measurements to determine that exposed parts are acceptably insulated from the supply circuit before returning the unit to the customer. Use the following checks to perform these measurements: A. Leakage Current Hot Check-With the unit completely reassembled, plug the AC line cord directly into a 120V AC outlet. (Do not use an isolation transformer during this test.) Use a leakage current tester or a metering system that complies with American National Standards Institute (ANSI) C101.1 "Leakage Current for Appliances" and Underwriters Laboratories (UL) 1492 (71). With the unit AC switch first in the ON position, then in the OFF position, measure from a known earth ground (metal water pipe, conduit, etc.) to all exposed metal parts of the unit (antennas, handle bracket, metal cabinet, screw heads, metallic overlays, control shafts, etc.), especially any exposed metal parts that offer an electrical return path to the chassis. Any current measured must not exceed 0.5 milliamp. Reverse the unit power cord plug in the outlet and repeat test. ANY MEASUREMENTS NOT WITHIN THE LIMITS SPECIFIED HEREIN INDICATE A POTENTIAL SHOCK HAZARD THAT MUST BE ELIMINATED BEFORE RETURNING THE UNIT TO THE CUSTOMER. B. Insulation Resistance Test Cold Check-(1) Unplug the power supply and connect a jumper wire between the two prongs of the plug. (2) Turn on the power switch of the unit. (3) Measure the resistance with an ohmmeter between the jumpered AC plug and each exposed metallic cabinet part on the unit. When the exposed metallic part has a return path to the chassis, the reading should be between 1 and 5.2 Megohms. When there is no return path to the chassis, the reading must be "infinite". If it is not within the limits specified, there is the possibility of a shock hazard, and the unit must be repaired and rechecked before it is returned to the customer.

PROPRIETARY INFORMATION THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION OF BOSE® CORPORATION WHICH IS BEING FURNISHED ONLY FOR THE PURPOSE OF SERVICING THE IDENTIFIED BOSE PRODUCT BY AN AUTHORIZED BOSE SERVICE CENTER OR OWNER OF THE BOSE PRODUCT, AND SHALL NOT BE REPRODUCED OR USED FOR ANY OTHER PURPOSE.

2

ELECTROSTATIC DISCHARGE SENSITIVE (ESDS) DEVICE HANDLING
This unit contains ESDS devices. We recommend the following precautions when repairing, replacing, or transporting ESDS devices: · Perform work at an electrically grounded work station. · Wear wrist straps that connect to the station or heel straps that connect to conductive floor mats. · Avoid touching the leads or contacts of ESDS devices or PC boards even if properly grounded. Handle boards by the edges only. · Transport or store ESDS devices in ESD protective bags, bins, or totes. Do not insert unprotected devices into materials such as plastic, polystyrene foam, clear plastic bags, bubble wrap or plastic trays.

CD-20 MANUAL REVISION OVERVIEW
This service manual contains information about changes to the CD-20 PCB assemblies. It also includes the original service manual as well as the supplements (183884-S1, 183884-S2, 183884-S3) concerning the CD-20. The following PCB assemblies (as well as the original CD20 PCB) are covered by this service manual. PCB part number 199827 (has a slight change to the AM circuit to enable the use of a new AM antenna), PCB part number 250736 (incorporates a new FM section).

3

SPECIFICATIONS
Physical Dimensions: Weight: Top Cover: Bottom Cover: Display: Power Input: Line Level Inputs: Line Level Outputs: Zone 1: 2.6"H x 15.5"W x 8"D (6.6 x 39.4 x 20.3 cm) 5.9 lbs. (2.7kg) Brushed aluminum finish Plastic, Black Vacuum fluorescent 5mm coaxial power jack Tape, Aux, Video 1, Video 2 Tape Miniature 8-pin DIN connector Detachable power-pack, 12VAC, 1.6A RCA Jack pairs Right=Red, Left=White RCA Jack pair Right=Red, Left=White L/R fixed line level audio, L/R variable line level audio, DC turn on signal, speaker command data out, audio ground, and data ground L/R fixed line level audio, L/R variable line level audio, DC turn on signal, speaker command data out, audio ground, and data ground data out, data in, and ground 2.5mm mono jack USA/CSA "F" type EURO "PAL" type JAPAN "F" type Variable level output

Zone 2:

Miniature 8-pin DIN connector

Serial Data Port: Antenna Input:

3.5mm miniature stereo jack AM FM, 75

Headphone Connector:

3.5mm stereo jack FM Tuner (per IHF-T-200)

Channel Spacing:

US: 200 kHz EURO: 50 kHz JAPAN: 100 kHz US: 87.5 MHz-107.9 MHz EURO: 87.50 MHz- 108.00 MHz JAPAN: 76.00 MHz-90.00 MHz U.S./ Military version: 75µs EURO version: 50µs JAPAN version: 50µs US: 12 dBf nominal/ 17 dBf limit EURO: 17 dBf nominal/ 22 dBf limit JAPAN: 12 dBf nominal/ 17 dBf limit 4

Band Limits:

De-emphasis:

Usable Sensitivity:

SPECIFICATIONS
FM Tuner (per IHF-T-200) (continued) 50 dB Quieting Sensitivity; Mono: US: 15 dBf nominal/ 20 dBf limit EURO: 20 dBf nominal/ 25 dBf limit JAPAN: 20 dBf nominal/ 25 dBf limit US: 37 dBf nominal/ 42 dBf limit EURO: 42 dBf nominal/ 47 dBf limit JAPAN: 37 dBf nominal/ 42 dBf limit Mono: 75 dB nominal/ 70 dB limit Stereo: 65 dB nominal/ 60 dB limit Mono: 0.2% nominal/ 1.0% limit Stereo: 0.3% nominal/ 1.5% limit 1.5 dB nominal/ 2.5 dB limit 60 dB nominal/ 50 dB limit US: 70 dB nominal/ 65 dB limit EURO: 75 dB nominal/ 70 dB limit JAPAN: 70 dB nominal/ 65 dB limit US: 45 dB nominal/ 40 dB limit EURO: 85 dB nominal/ 70 dB limit JAPAN: 45 dB nominal/ 40 dB limit 60 dB nominal/ 50 dB limit 55 dB nominal/ 45 dB limit ± 0.5 dB nominal/ ± 1.5 dB limit 40 dB nominal/ 25 dB limit 32 dBf ± 3 dB 12 dB nominal/ 7 dB limit AM Tuner (per IHF-T-100) Channel Spacing: US: 10 kHz EURO: 9 kHz JAPAN: 9 kHz US: 530 kHz - 1710 kHz EURO: 522 kHz - 1611 kHz JAPAN: 522 kHz - 1629 kHz 55 dBµV/m nominal/ 60 dBµV/m limit 60 dB nominal/ 50 dB limit 45 dB nominal/ 35 dB limit 40 dB nominal/ 30 dB limit 5 IHF standard test loop at 45 dBf 30 Hz - 15 kHz at 1 kHz at 45 dBf at 45 dBf at 65 dBf US = ± 75 kHz deviation EURO = ± 40 kHz Deviation at 65 dBf

Stereo:

Signal to Noise Ratio:

Harmonic Distortion: Capture Ratio: AM Rejection: Alternate Channel Selectivity: Image Rejection:

RF Inter-modulation: Sub-carrier Product Rejection: Frequency Response: Stereo Channel Separation: Auto Stop Level: Adjacent Channel Selectivity:

Band Limits:

Usable Sensitivity: Alternate Channel Selectivity: Adjacent Channel Selectivity: Image Rejection Ratio:

SPECIFICATIONS
Signal to Noise Ratio: Distortion: Frequency Response: Auto Stop Level: AM Tuner (per IHF-T-100) (continued) 50 dB nominal/ 45 dB limit 1.0% nominal/ 2.0% limit 40 Hz: -3 dB nominal/ -6 dB limit 2 kHz: -3 dB nominal/ -6 dB limit 60 dBuV/m ± 3 dB Preamplifier Input Impedance: Output Impedance: Output Voltage: AUX/ VIDEO 1, 2 = 33k TAPE = 48k Zone 1, 2 =:220 TAPE: = 220 FM: 0.6 Vrms AM: 0.4 Vrms CD: 2.0 Vrms 31 mW ±2 dB 2.0 Vrms ± 2 dB .02% nominal/ .08% limit ± 0.5 dB nominal/ ±1.0 dB limit 115 dB nominal/ 100 dB Limit 70 dB nominal/ 50 dB limit 1 mV nominal/ 10 mV limit -100 dB nominal/ -90 dB limit CD Player Digital to Analog Process: Maximum Output Level: THD + Noise: Signal to Noise Ratio: Channel Separation: Frequency Response: Low-level Linearity Error: Dynamic Range: 4X Over-sampling, dual one bit D/A 2.0 V ± 2 dB 0.03% nominal/ 0.12% limit 90 dB nominal/ 85 dB limit 70 dB nominal/ 50 dB limit ± 0.5 dB nominal/ ± 1.0 dB limit 5.0 dB nominal/ 10.0 dB limit 95 dB nominal/ 90 dB limit at 1 kHz, 0 dB A-weighted at 1 kHz 20 Hz - 20 kHz -90 dB pk, max. vol. ±30%, 1 kHz, max volume ±40%, 1 kHz, max volume ±10%, 1 kHz, max volume Mono/ 75 kHz dev. 30% mod., 100 dBuV/m ABEX TCD-782 TNO2 32 load, 1 Vrms Aux input THD <0.15% 1 kHz, THD < .12% Output = 1 Vrms 20 Hz- 20 kHz A-weighted, max volume at 100 dBµV/m at 100 dBµV/m at 100 dBµV/m, 0 dB @ 400 Hz

Headphone Output: Maximum Output Level: THD: Frequency Response: Signal to Noise Ratio: Channel Separation: Switching "pops" and "clicks": Muting, Zone 1 and 2 outputs:

6

SPECIFICATIONS
CD Player (continued) Defect Tracking (interruption): Defect Tracking (black dot): Defect Tracking (scratch): Defect Tracking (finger print): Defect Tracking (warped disc): 1.0 mm nominal/ 0.8 mm limit 1.0 mm nominal/ 0.8 mm limit 1.6 mm nominal/ 1.0 mm limit 75 µm nominal/ 65 µm limit 1.0 mm nominal/ 0.7 mm limit ABEX Test Disk TCD-725R ABEX Test Disk TCD 725R ABEX Test Disk TCD-721R ABEX Test Disk TCD-725R ABEX Test Disk TCD-732RA ABEX Test Disk TCD-714R Phillips TS4, TNO 1-15

Defect Tracking (eccentric disc): 210 µm nominal/ 140 µm limit Cueing Time: De-emphasis Error: Disc Access Time: Disc Unload Time: 2 sec nominal/ 3 sec limit 5 kHz: -4.53 dB ± 2 dB 16 kHz: -9.04 dB ± 2 dB 5 seconds nominal/15 seconds limit 5 seconds nominal/15 seconds limit

Any disc playing to any other disc playing Any disc playing or stopped to ejected magazine

7

THEORY OF OPERATION
1.0 Overview The CD-20 is a self-contained CD player with a 6-disc changer, AM/FM tuner, preamplifier, and control center for use with Bose® powered speaker systems. In addition to the two internal sources (CD and tuner), it allows for up to four external audio sources to be connected (Tape, Aux, Video 1 and Video 2). It uses an RF remote control, allowing it to be operated from different rooms within a house without the line-of-sight restrictions of an IR remote. No CE-1 type functionality has been included. All Smart Speaker data commands (i.e.-for AM-25P) have been implemented. The CD-20 has two independent output zones, similar to CD-10, accessible through circular DIN connectors in the back of the product. This allows Zone 1 to play any of the six possible audio sources, while Zone 2 plays the same source (or any other audio source) simultaneously. The only restriction is that AM and FM cannot be played simultaneously (there is only one tuner source, usable in only AM or FM mode at a given time). 2.0 Power Supply Electronics (Schematic Diagram Sheet 1) The unit is powered by an external 12 VAC power supply capable of delivering 1.6 Amps RMS. D12, D1 and C3 form a positive half-wave rectifier that supplies voltage to the CD_VCC regulator transistor Q10 (which powers the CD mechanism). Feedback components R23, D13 and R24 sample the CD output voltage, divide it down, and apply it to Q11's emitter. Q11 keeps Q10 turned on until the CD_VCC voltage reaches the desired level. Once CD_VCC reaches about 14.5 volts, Q10 goes linear and keeps the output voltage from going any higher. To disable the CD_VCC supply, the CD_RES line is set to +5V by the microprocessor, which turns Q1 and Q2 on. Q1 keeps Q11 turned off, while Q2 quickly shorts CD_VCC to ground (turning the CD mechanism off immediately). R2, D4 and C6 form a positive half-wave rectifier that supplies voltage to +5V regulator IC U1. The +5V circuit powers the microprocessor and EEPROM. The microprocessor monitors the DETECT line (via comparator U402) in case of a power failure. D5 and C10 form a positive half-wave rectifier that supplies voltage to +10V regulator IC U2. The +10V supply powers all the audio circuitry, the tuner, and the enable lines for the external powered speakers. C24, R28, R29 and C21 form a resistor/capacitor AC voltage divider that provides the 4.2 VAC for the VFD (display) filament. The -30 Vdc and -24 Vdc supplies are also for the VFD, and are generated using a negative voltage tripler. D6, D9, D7, C15, C23, and C18 form the tripler. R11 and zener diode D18 regulate the tripled voltage to -30V. The -24 Vdc supply is divided down from the -30 Vdc by R26, R12 and R14. The enable lines (also referred to as +10V control lines) for the powered speakers (Z1_ENBL and Z2_ENBL) are powered by Q102 and Q104. Q101 and Q103 provide base turn-on current when the microprocessor sets Z1_ENBL or Z2_ENBL to +5V. The output of the enable lines is current-limited to less than 100 mA by R134 and R138. This protects against accidental shortcircuits in the speakers or their cables.

8

THEORY OF OPERATION
3.0 Control Electronics (schematic Diagram Sheet 3) The audio circuits, tuner, CD mechanism, display, EEPROM, remote receiver, push buttons, and AC power status are all overseen by microprocessor (micro) U400. The micro is clocked by an 8 MHz ceramic resonator (X401) and is given a reset pulse by U403 (the reset IC). This occurs whenever the +5V power supply falls below about 4.75V and automatically at power-up. The micro communicates with all three audio chips (U100, U101, and U102) using a three wire interface (clock, data and ground). In all three cases, the clock line is the ACLOCK line, port P35 on the micro. Depending on which chip is being addressed, the micro may use either the ADATA_1 or ADATA_2 lines to send the data. The data is sent in I2C format to all three chips. The micro sends commands to the audio chips whenever new input sources are selected, or the volume needs to change, or a zone needs to mute or unmute. The micro changes AM and FM tuner stations by writing to the PLL (Phase-Locked Loop) chip U302. This information is sent using the same clock and data lines used for the audio chips (ACLOCK and ADATA_2). However, the PLL chip enable (PLL_CE) must also be high for the chip to receive the message. The micro can tell when a station is strong enough to stop seeking by monitoring the RF_SIG/ line from U300 (the LA1851 detector chip). The micro can then check to see if that same station is transmitting a valid carrier (in case an adjacent station was strong enough to fool it into stopping) by asserting the F_TEST line. The result of the frequency test is signaled to the micro by the RF_F_OK line. The CD-20's 6-disc CD mechanism is a complete (mechanical as well as electrical) assembly that is purchased as an OEM unit from FMS (Ford Mazda Sanyo). It comes with its own microprocessor-based controller PCB that is capable of many functions. The CD-20's micro communicates with this PCB via a dedicated serial data bus (CD_BUS, micro port P12). The CD-20 micro (U400) sends control commands (play, pause, stop, skip forward, etc.) to the mechanism via the CD_BUS line, and receives disc, track, etc., information in the same way. The CD mechanism is enabled by U400 by dropping the CD_RES (CD reset) line and raising the CD_ENBL (CD enable) line. The appropriate control commands are then sent. The micro controls the vacuum fluorescent display (VFD400) with its on-chip VFD driver. The driver scans the display's grids and segments automatically using ports P7, P8 and P9. The CD-20 display is divided into 8 groups, each enabled by a separate grid line (G1 through G8). Each of these groups contains up to 15 icons. Each icon is enabled by a separate segment line (S1 through S15). Although icons appear to be lit constantly, in fact each is actually turning on and off at a rate too fast to see. Each of the 8 groups of icons are only enabled 1/8th of the time (first group 1, then group 2, etc., in a repeating sequence). The segment lines are used to select which icons should be lit as each icon group gets enabled. The 511 series resistors are added to reduce scan currents that might interfere with AM tuner reception. All series resistors and inductors on the +5V, +10V, -24V and -30V power supply lines are similarly added to reduce tuner interference. U401 is a 1k-bit (128 bytes x 8) EEPROM (Erasable, Programmable Memory) that stores the AM and FM station presets, RF remote House Code and background (self-test) information. Whenever a new preset is stored or erased by the user, information gets written to U401. The micro communicates with the EEPROM using a three wire interface that is identical (but separate) to the interface used for the audio chips. In this case, the clock line is the EE_CLK signal, port P03, and the data line is the EE_DATA signal, port P04. Although this data is also sent using the I2C format, the EEPROM is busy enough to have its own interface (rather than sharing the audio chip's interface). 9

THEORY OF OPERATION
3.0 Control Electronics (continued) The micro monitors messages from the RF remote control with input port P30 (RF_DATA). RF receiver module RR100 demodulates the signals received on the CD-20's remote antenna (the digital ground conductor in the audio output cables) and converts it into a low-level AC signal. This signal is filtered and converted to TTL levels by one-half of comparator U402 before it is fed to the micro. Key closures are detected by means of the micro's on-chip A/D converter. When a console key is pressed, the voltage divider formed by R419 and R420 is changed by the switch being pushed. Specifically, a new resistor will be shunted across either R419 or R420. This increases or decreases the voltage at the micro sense lines, KEY_IN1, KEY_IN2 or KEY_IN3 (note that the keys are divided into 3 groups of 4 keys each). The micro examines these sense lines and determines which key is pressed based on the voltage it measures. If the micro measures a voltage of about 2.5 volts, it knows no key is pressed within that particular group of 4. The AC power status is monitored by the micro using port P10, pin 1 of U400 (PFAIL/). When the AC input voltage to the wall transformer falls, its AC output voltage falls below the nominal 12V. When the voltage falls below a certain point (about 88 VAC in FM mode, about 93 VAC in CD mode), the DETECT line from the power supply (which monitors the raw DC input voltage to the +5V regulator, U1) causes comparator U402's output to go low. This warns the micro that the power is failing, and it responds by shutting the system down (muting the speaker outputs, blanking the display, etc.). When AC power is OK, U402's output (PFAIL/) is high. 4.0 Audio Electronics (Schematic Diagram Sheet 2) The CD-20 has 2 internal audio sources (CD and tuner) and four external sources (Tape, Aux, Video 1 and Video 2). All of the sources get routed through audio matrix chip U101. This IC controls which zone(s) the sources will be connected to. The chip has three left and right outputs. One is used for Zone 1, two for Zone 2, and three for the tape outputs. The micro instructs the chip to connect each of the outputs to the correct input by using the clock and data lines as described above. If a zone is not active (or muted), the audio matrix chip may connect that output to an internal reference rather than one of the inputs for extra muting. The matrix has internal buffer amps, allowing its outputs to be used directly as the Zone 1 and Zone 2 fixed audio outputs. Output #3 from U101 (pins 16 and 17) is used for the CD-20's left and right Tape output. The micro sees to it that this output nominally is connected to the same input source as the Zone 1 output. This means that any tape deck connected to the Tape outputs would record the same source that is being played on Zone 1. However, if the Tape input is selected for Zone 1, the Tape outputs are muted by the micro to prevent a feedback loop. The first two matrix chip outputs (pins 12 through 15), as described, are then fed to Zone 1 and Zone 2 volume control ICs (U100 and U102 respectively). Each IC contains the volume-control cell, output-buffer cell and output mute cell for that particular zone. Volume settings, mute settings and output-buffer switching are all controlled by the micro using the ACLOCK, ADATA_1 (for Zone1) and ADATA_2 (for Zone2) lines. The final LR audio outputs (called the "adjustable outputs," after volume control and muting) are pins 24 and 25. From here, the audio passes through DC blocking capacitors C114, C214, C124 and C224 (the volume control ICs run on a single +10V supply, so the audio has a 5 Vdc offset component) before running to output circular DIN connectors J101A and J101B. 10

THEORY OF OPERATION
4.0 Audio Electronics (continued) Each of the volume control chips has two independently mutable outputs. The #1 outputs are used for the speakers (as described above). The #2 output of the Zone 1 volume chip is used for CD-20's Headphone output (the #2 output on the Zone 2 chip is not used). Anyone plugging in headphones would therefore hear the same source that was previously being played by the Zone 1 speakers. The microprocessor monitors the HP_SENSE line from the headphone jack to tell if headphones are plugged in. When they are, the micro mutes the #1 outputs from the Zone 1 volume chip (to the speakers), and unmutes the #2 outputs (to the headphones). The opposite occurs when headphones are unplugged. The headphone signals are buffered by U104 in order to drive the required 32 loads. Audio from the CD player typically contains a great deal of motor noise. This noise occurs because of ground conductor voltage drops on the ribbon cable connecting to the mechanism. To eliminate this motor noise, op-amp U103 has been configured as a differential amplifier. Any motor noise signals on the left and right audio lines are also on the ground reference line, pin 2 of the CD ribbon cable (pin 2 of connector J110). Therefore, U103 eliminates this commonmode component without affecting the actual audio (which is purely a differential-mode component). At the same time, U103 provides the necessary gain for the CD signal. 5.0 Tuner Electronics (Schematic Diagram Sheet 4) The FM antenna signal comes in through F connector J301 and enters the FM front-end module (U301). U301 contains a tuned RF amplifier, the FM local oscillator, and the first mixer. The 10.7 MHz IF output signal appears on pin 4 and is passed through a 10.7 MHz ceramic filter (CF300). The filter's output is amplified by the first IF gain stage. This stage consists of Q307, Q308 and their associated components. The signal is then passed through a second ceramic filter (CF301), a second gain stage (Q309, Q310, etc.) and a third ceramic filter (CF302). These filter stages reject unwanted FM stations and noise. The output of the final ceramic filter is fed into the main detector IC (U300). This device contains a second mixer, the FM detector, FM stereo MPX decoder, stop-level detection, as well as most of the AM circuitry. U300 further amplifies the IF signal and then performs FM detection using a double tuned quadrature detector formed by T303 and T304. T304 is adjusted for FM center frequency by adjusting it for 0 VDC between the AFC terminal (pin 4, U300) and the VREG terminal (pin 28, U300). T303 is adjusted for minimum distortion. (These two adjustments are interactive, so a few repetitions may be required.) The recovered audio appears on pin 8 of U300. The recovered audio is filtered by C326 and the associated components and fed back into U300 on pin 9. U300 performs the FM stereo MPX decoding and outputs the decoded L and R channels (when FM is selected) on pins 14 and 15. The separation is controlled by the resistance from pin 12 to ground. The PLL decoder is clocked by 456 kHz resonator X300. The PLL loop filter components are connected to pin 11. The FM stop level is set by the variable resistance R349 on pin 30 and is nominally set to 33 dBf. The signals are buffered and amplified by op-amp U303 and its associated components. Components R301, C302, R305, and C303 perform FM de-emphasis. MPX filters T301 and T300 remove any unwanted out-of-band signals.

11

THEORY OF OPERATION
5.0 Tuner Electronics (continued) The signal from the AM loop antenna enters the unit through the 2.5 mm AM jack (J300) and is fed to the AM front end module (T302). This device contains an RF tuned section and the AM local oscillator tuner circuit. The tuned output appears on pin 12 and is fed to the AM buffer FET transistor Q303. The buffered output is sent to pin 27 of U300 which contains the AM RF amplifier, mixer, IF amplifier, AM detector, and AM stop level detection. The AM stop level is set by the variable resistor R348 on pin 16 and is nominally set at 70 dBuV/m. The AM IF output signal appears on pin 26. This signal is filtered by the IF filter T306 and fed back into the chip on pin 24 for AM detection. The AM detected output appears on pin 5 where it is filtered by C327, R328 and C328. The filtered output is fed back into U300 on pin 6 where it is sent to the L and R outputs (when AM is selected), pins 14 and 15. The AM and FM local oscillators are controlled by the PLL IC (U302). This device is instructed by the micro to select either AM or FM and to tune to a particular frequency. The PLL reference oscillator is clocked by a 7.2 MHz crystal (X301). This frequency is divided down to 400 kHz and then appears on pin 7. U302 divides down the Local Oscillator (LO) frequency and compares it to an internal reference frequency. An error signal from the comparison appears on pin 18. This error signal is integrated and filtered by Q304, Q305, and associated components. This produces the tuning voltage which appears at the collector of Q304. The tuning voltage is filtered by R312, C316, R311, and C309 and fed to pin 14 of the AM front end (T302). Here it is used to vary the capacitance of 2 varactor diodes. The first diode adjusts the frequency of the AM local oscillator. The second tunes the AM RF input section to the desired frequency. Similarly, in FM mode, the tuning voltage is filtered by R316 and C321 and fed to the FM front end. As in the AM case, the FM front end uses this voltage to vary the LO frequency and to tune the RF input sections.

12

THEORY OF OPERATION

Figure 1. CD-20 Block Diagram 13

DISASSEMBLY/ASSEMBLY PROCEDURES
Note: Refer to Figures 2 and 3 for the following procedures. Numbers in parentheses correspond to the item callouts in Figures 2 and 3. 1. Top Cover Removal 1.1 Grasp the cover (1) by the edges and work it up to release the christmas tree fasteners from the superstructure (2). This might take some effort. Using a flatblade screwdriver may be helpful. Take care not to damage the top cover. 2. Top Cover Replacement 2.1 Align the cover's christmas tree fasteners with the holes in the superstructure (2). Push the cover (1) down until it is fully seated. Note: Align the cover so that the BOSE® logo is in the left corner. 3. Display Window Removal 3.1 Grasp the top edge of the display window (3) and pull it forward. 4. Display Window Replacement 4.1 Align the display window (3) so the catches are facing up. 4.2 Align the display window with the LCD and press it into the superstructure (2). 5. Superstructure Removal 5.1 Perform procedures 1 and 3. 5.2 Remove the door spring (7) from the superstructure (2) and door assembly (8). 5.3 Remove the ribbon cable (6) from the super structure and disconnect it from the PCB (18). Note: Make a note of how the ribbon cable was dressed in the rear channel of the superstructure. 6.4 Replace the three screws (4) that secure the superstructure to the base. 6.5 Replace the door spring (7) to the superstructure and door assembly (8). 6.6 Perform procedures 2 and 4. 7. Door Assembly Removal Note: Refer to Figure 3 for the following procedures. 7.1 Perform procedure 5. 7.2 Lift the door assembly (8) straight up. 8. Door Assembly Replacement 8.1 Lower the door assembly (8) into the base (9) aligning the post (10) on the door assembly to the holes (11) in the base. Also rotate the hinge (12) on the left side of the door so that the groove fits into the slot on the hinge holder (13). 8.2 Perform procedure 6. 14 5.4 Remove the three screws (4) from the superstructure. 5.5 Place a flat-blade screwdriver into each of the four slots (5) on the superstructure and push away from the center of the unit to release the catches. 5.6 Lift the superstructure away from the base (9). 6. Superstructure Replacement 6.1 Lower the superstructure (2) onto the base (9) and pull the ribbon cable through the large opening. 6.2 Push down on the superstructure (2) until it snaps into the base (9). 6.3 Redress the ribbon cable in the channel at the rear of the superstructure (2). Connect the cable to the PCB.

DISASSEMBLY/ASSEMBLY PROCEDURES
9. CD Mechanism Removal 9.1 Perform procedure 5. 9.2 Lift the CD mechanism (14) straight up from the base (9). 10. CD Mechanism Replacement 10.1 With the opening of the CD mechanism facing towards the front of the unit, lower the CD mechanism into the base (9) aligning the four grommets (15) with the four posts on the base (two not shown). Note: Make sure the four springs (16) are located on the four outer posts of the base. 10.2 Perform procedure 6. 11. Control Panel Removal 11.1 Perform procedure 5. 11.2 Grasp the top edge of the control panel (17) and pull it forward. 12. Control Panel Replacement 12 1 Tilt the control panel (17) forward and place it into the base (9) so that the lower edge of the control panel is in front of the catches on the base. Tilt the control panel towards the rear of the base until the control panel snaps into place. 13. PCB Assembly Removal 13.1 Perform procedure 5. 13.2 Grasp the PCB assembly (18) and lift it straight up. 13.3 The RCA jack PCB (19) and the headphone PCB (20) are wired to the PCB assembly. Lift the RCA Jack PCB and the headphone PCB straight up. Note: When removing the PCB, make a note of the wire dressing for reinstallation. 16. PCB Assembly Replacement 16.1 While lowering the PCB assembly (18) into the base (9), angle it so that the RCA jacks protrude out the rear of the base. 16.2 Insert the RCA Jack PCB (19) into the holes in the base marked "TAPE IN, TAPE OUT". The superstructure (2) will give mechanical support to the RCA Jacks. 16.3 Insert the headphone PCB (20) with connector J612 up, into the slot. 16.4 Redress all wires. 15. PCB Assembly (Assemble) 15.1 Connect the power supply (21) and the tuner PCB (22) to the main PCB by plugging them into the main PCB (23) via connectors: J3 and J4 on the power supply PCB, J306 and 307 on the tuner PCB. Tabs on the tuner and power supply PCB lock into slots on the display PCB (24) to create a mechanical support. 14. PCB Assembly (Disassemble) 14.1 The power supply PCB (21) and the tuner PCB (22) are plugged into the main PCB (23). Grasp the power supply PCB or the tuner PCB and pull in an outward direction from the main PCB.

15

Figure 2. Disassembly/Assembly View

16

HINGE 12

8

12 10

9
11

13

FRONT VIEW HINGE HOLDER

Figure 3. Exploded View of Door

17

RC-20 REMOTE DISASSEMBLY/ASSEMBLY
Note: Numbers in parentheses correspond to the callouts in Figure 4. 1. Enclosure Disassembly 1.1 Slide off the battery compartment door (5) and remove the batteries. 1.2 While holding the top cover (4) with one hand, place your fingers from your other hand in the battery compartment and grasp the lower part of the bottom cover (3) with your finger tips. 1.3 With your finger tips in the battery compartment, first pull parallel to the unit then pull perpendicular. 1.4 With the catches released at the bottom, work your fingers up the sides to release the rest of the catches. 2. Enclosure Assembly 2.1 Lower the bottom cover (3) onto the top cover (4) so that the bottom cover's lip fits over the top cover. 2.2 Press the top cover and bottom cover together until they snap into place. 3. PCB Removal 3.1 Lift the PCB (1) straight up. The springs will come up with the PCB. 4. PCB Replacement 4.1 Lower the PCB (1) into the bottom cover (3) so that the springs are in the battery compartment. 5. Pad Removal 5.1 The pad (2) is not secured. Grasp a corner of the pad and lift it out. 6. Pad Replacement 6.1 Lower the pad (2) into the top cover (4) so that the buttons line up with the holes in the top cover.

5 3

10

1

6

2 7 9 11

8

CATCHES

4 CATCHES

Figure 4. RC-20 Disassembly/Assembly View 18

CD MECHANISM DISASSEMBLY PROCEDURES
1. Main PCB Disassembly 1.1 Short the two pads on the ribbon cable coming from the pick up. 1.2 Unplug CN905. 1.3 Remove the four screws that secure the PCB to the chassis. 1.4 Lift the PCB up and remove the remaining connectors. 2. Base Chassis Disassembly 2.1 Remove all the FPCs that connect the mount chassis (A173) to the main PCB. 2.2 Remove the front and rear elevator tension spring (A59). 2.3 Remove the two E-rings located in the rear (A238) and the two located in the front (A241). Remove the two E-rings located in the front (A235) and the two located in the rear (A236). Remove the link cross bars (A107) and (A111). 2.4 Remove the screw (A133) and the two screws (A131) that mount the elevator unit and remove the elevator unit. Note: A133 is the screw that secures the plastic piece. 2.5 Remove the six screws (A61) that secure the top base chassis (A14). 2.6 Remove the two screws (A63) and the two screws (A64) that secures the rear base chassis (A22). Remove the spring that connects from the mount chassis to the base chassis. Note: Use caution when removing the mount chassis so that the washers, rollers, etc. that are mounted on the lift pin of the mount chassis are not lost. (Continued on the next page)

19

CD MECHANISM DISASSEMBLY PROCEDURES
Note: When installing the mount chassis (A173), line up the elevator shaft (A119) so that the lever (A55) is almost touching the eject lever (A45). The mount chassis should be at it's lowest position. 3. Elevator Motor Disassembly 3.1 Unplug the FPC (A104) from the PCB. 3.2 Remove the screw (A133) that secures the elevator unit. Note: A133 is the screw that secures the plastic piece. 3.3 Remove the two screws (A131) that secure the elevator unit to the base chassis and remove the elevator unit. Lift the elevator unit out through the bottom of the base chassis. 3.4 Remove the FPC (A104) from the motor (A127) terminal with a soldering iron. 3.5 Remove the screw (A130) that secures the elevator motor bracket (A115) to the elevator unit bracket. 3.6 Remove the two screws (A132) that secure the motor to the motor bracket.

20

CD MECHANISM DISASSEMBLY PROCEDURES
4. Feed Motor Disassembly 4.1 Remove the washer (A102) and then remove the DV middle gear (A81). 4.2 Remove the FPC from the feed motor with a soldering iron. 4.3 Remove the two screws (A94) that secure the feed motor (A89). Lift the motor up. 5. Loading Motor Disassembly 5.1 Unplug the FPCs (A104) and (A232). 5.2 Remove the four screws (A64) that secure the base chassis side (A19) to the base chassis. 5.3 Remove the screw (A133) that secures the elevator unit to the chassis. Remove the base chassis side (A19). The elevator unit will be attached to the base chassis side. 5.4 Remove the two screws (A246) that secure the loading motor unit to the base chassis. 5.5 Remove the FPC (A232) that is connected to the motor terminal with a soldering iron. 5.6 Remove the two screws (A242) that secure the motor (A233) to the motor mount. Note: Assemble in the reverse order of the disassembly and make note of the following. 1. Make sure the front bend of the friction gear arm assembly (A197) is inserted in the square hole of the chassis mount (A173). 2. Make sure that the PR cam roller (A223) is fitted to the push cam rod (A215) and is inserted in the bend groove of the push rod (A221). 3. The tightening torque of the motor mounting screw (A242) is 1.5 to 2.0 kg-cm. 21

CD MECHANISM DISASSEMBLY PROCEDURES
6. Lift Motor Disassembly 6.1 Perform procedure 3. 6.2 Remove the two DL springs (A228) that are located on both sides. The DL springs are black. 6.3 Remove the FPC from the lift motor (A154) with a soldering iron. 6.4 Grasp the unit where the DL springs were located and rotate the motor assembly section up. Remove the two screws (A157) that secure the motor bracket to the assembly. Note: Rotate the worm gear A148 until the disc rollers are in contact. 6.5 Remove the E-ring (A156) and the washer (A166) that secures the worm gear to the motor shaft. 6.6 Remove the screw (A158) that secures the motor to the motor bracket. 7. Pick Up Disassembly 7.1 Short the short pattern located on the FPC (A1) with a soldering iron. Unplug the FPC (A1). 7.2 Remove the screw (A101) that secures the FPC to the chassis. Make note of the location of the FPC that is glued to the chassis. 7.3 Remove the two screws (A96) that secure the screw clip (A78), DV plate spring (A86) and DV spring holder (A76) to the pick up (A87). 7.4 Remove the screw (A97) that secures the switch spacer to the chassis. 7.5 Remove the two screws (A93) that secure the sub shaft (A73) of the pick up to the chassis. Lift the pick up out of the unit.

22

CD MECHANISM DISASSEMBLY PROCEDURES
Note: When replacing the pickup, grease the main shaft and the U groove of the sub shaft. After securing the FPC, apply glue to the end opposite the screw. 8. Manual Magazine Ejection 8.1 With the disc clamped, rotate the lift motor worm gear (A148) 25 to 28 turns in the direction of the arrow to unclamp the disc. 8.2 With the disc unclamped, rotate the L wheel worm gear (A212) in the direction of the arrow to return the disc to the magazine. Note: If the disc comes in contact with the separator and can not be returned, push the edge of the disc up or down so that it returns without coming into contact with the separator of the magazine. 8.3 After returning the disc to the magazine, push the emergency eject plate (A51) with the tip of a screwdriver to remove the magazine.

23

TEST PROCEDURES
General Test Setup Use cable 184209 for fixed level tests. Use cable 183174 for adjustable level tests. The miniature switch number 8 on the remote must be up to control ZONE 2. For ZONE 1 and 2 variable tests, adjust the volume to max. Terminate the Headphone output into 32. Terminate all Audio outputs into 10K. Terminate the serial output jack (tip and ring) into 10k (two resistors). See Figure 5 for adjustment locations. OUTPUT 1. Aux Gain and Separation Test 1.1 Apply a 2 Vrms, 1 kHz signal to the left AUX input. 1.2 Ground the TAPE, VIDEO 1, VIDEO 2 and right AUX inputs. 1.3 Reference a dB meter to the applied signal. 1.4 Measure the gain according to the chart below. Note: Repeat this test for the right channel. 3.3 Reference a dB meter to the applied signal. OUTPUT Zone 1 L Fixed Zone 1 L Adjustable Zone 2 L Fixed Zone 2 L Adjustable Tape L Headphone L Zone 1 R Fixed Zone 1 R Adjustable Zone 2 R Fixed Zone 2 R Adjustable Tape R Headphone R MIN dB MAX dB -1.5 1.0 -1.5 1.0 -1.5 1.0 -1.5 1.0 -1.5 1.0 --50 --50 --50 --50 --50 --50 --50 3.4 Measure the gain according to the chart below. Note: Repeat this test for the right channel. OUTPUT Zone 1 L Fixed Zone 2 L Fixed Zone 1 R Fixed Zone 2 R Fixed MIN dB MAX dB -1.5 1.0 -1.5 1.0 --50 --50 Zone 1 L Fixed Zone 1 R Fixed Zone 2 L Fixed Zone 2 R Fixed Tape L MIN DB -1.5 --1.5 --MAX DB 1.0 -50 1.0 -50 -50 2. Video Gain And Separation Test 2.1 Apply a 2 Vrms, 1 kHz signal to the left VIDEO 1 input. 2.2 Ground the TAPE, VIDEO 2, AUX and right VIDEO 1 inputs. 2.3 Reference a dB meter to the applied signal. 2.4 Measure the gain according to the following chart. Note: Repeat this test for the right channel and VIDEO 2.

3. Tape Gain and Separation Test 3.1 Apply a 2 Vrms, 1 kHz signal to the left TAPE input. 3.2 Ground the VIDEO 1, VIDEO 2, AUX and right TAPE inputs.

24

TEST PROCEDURES
4. Volume Control Mute Test 4.1 Apply a 2 Vrms, 1 kHz signal to the AUX input. 4.2 Set the volume control to maximum. 4.3 Reference a dB meter to ZONE 1 adjustable output. 4.4 Set the volume control to minimum and measure ZONE 1 output (should be -80 dB). 5. Distortion Test 5.1 Apply a 1 Vrms, 1 kHz signal to the AUX input (Volume at full). 5.2 Measure the distortion at ZONE 1 and ZONE 2 (should be .05% A-weighting). 6. Frequency Response Test 6.1 Apply a 1 Vrms, 20Hz signal to the AUX input (Volume at full). 6.2 Reference a dB meter to the applied signal. 6.3 Measure ZONE 1 and ZONE 2 output (should be ± 1 dB). 6.4 Apply a 1 Vrms, 20 kHz signal to the AUX input. 6.5 Reference a dB meter to the applied signal. 6.6 Measure ZONE 1 and ZONE 2 output (should be ± 1 dB). 7. Serial Data Interface Port 7.1 The voltage at the ring of the serial data jack should be 4.5 VDC. 7.2 The voltage at the tip of the serial data jack should be 0.8 VDC. 7.3 While adjusting the volume up or down, the voltage at the tip should be .6 VDC. 8. FM Alignment 8.1 Select FM and tune to 98.1 MHz. Inject an RF signal into the FM antenna terminals at 40 dBf, mono modulation, pilot off. 8.2 Front End Mixer Coil Adjustment: Connect a DC meter to U300, pin 25. Adjust the FM front end mixer coil for maximum DC voltage (should be within +0, -20 mV of peak value). Note: The front end mixer coil is located in the front end module (it is the only adjustable coil). Note: Do not perform the following test for PCB 250736. 8.3 FM Detector Zero adjustment: Connect a DC meter to the positive (+) side of C315 and the positive (+) side of C313. Adjust T304 for 0 Vdc ± 110mV. 8.4 FM Distortion adjustment: Adjust T303 for minimum distortion (viewed at tape output). 8.5 FM distortion should be < .6%. If the distortion is out of spec, repeat 8.3 and 8.4. Recheck FM distortion. 9. FM Stereo Separation 9.1 Inject an RF signal into the FM antenna terminal at 65 dBf, L only modulation, pilot on. 9.2 Connect a dB meter to the left TAPE output. Reference the dB meter to this point. 9.3 Connect the dB meter to the right TAPE output. The output should be -25 dB.

25

TEST PROCEDURES
10. FM Stop Level Adjustment Note: Do not perform the following test for PCB 250736. 10.1 Inject an RF signal into the FM antenna ternimals at 25 dBf, L+R modulation, pilot off, set to 98.1 MHz. 10.2 Connect a DC meter to pin 21 of U300. 10.3 Rotate R439 counterclockwise until the voltage becomes less than 2.5V, then clockwise until the voltage becomes greater than 2.5V. The correct adjustment is when the voltage just becomes sightly greater than 2.5V. 10.4 Increase the RF generator to dBf and confirm that the voltage at pin 21 U300 is less than 2.5V. 11. FM Sensitivity / SNR 11.1 Inject an RF signal into the FM antenna terminals at 42 dBf, L=R modulation, pilot on. 11.2 Connect a dB meter to the TAPE output. Reference the dB meter to this point. 11.3 Turn the modulation off and measure the output. The output should be -50 dB for US versions and -45 dB for European versions. 12. AM RMS 12.1 Inject an RF signal at a field strength of 70 dBu into the AM antenna terminals. 12.2 Connect an AC meter to the tape output. 12.3 Tune the generator and the unit t 630 kHz. Adjust the black slug of T302 for maximum output. The output should be 300 mVrms. 12.4 Tune the generator and the unit to 1080 kHz. Adjust the brown slug of T302 for maximum output. 12.5 Repeat steps 12.3 and 12.4 until maximum output is obtained. 13. AM Sensitivity 13.1 Inject an RF signal, 1080 kHz, at a field strength of 70 dBu to the AM antenna terminals. 13.2 Connect a dB meter to the TAPE output and reference it to this point. 13.3 Remove the RF signal and measure the TAPE output (should be - 30 dB). 14. AM Stop Level adjustment 14.1 Inject an RF signal at a field strength of 59 dBu to the AM antenna terminal. 14.2 Connect a DC meter to pin 21 of U300. 14.3 Rotate R348 counterclockwise until the voltage becomes less than 2.5V, then clockwise until the voltage becomes greater than 2.5V. The correct adjustment is when the voltage just becomes slightly greater than 2.5 VDC. 14.4 Increase the generator output to 64 dBu and confirm the voltage at pin 21 of U300 is less than 2.5V.

26

TEST PROCEDURES
15. CD Tracking Ability 15.1 The test discs listed in the chart below should be played with no audible defects. 15.2 If the unit fails any of these tests, replace the CD mechanism assembly or proceed to the Alignment procedures. Disc ABEX test disc TCD-725A ABEX test disc TCD-725A ABEX test disc TCD-725A ABEX test disc TCD-732R ABEX test disc TCD-713R Test Defect tracking (void), 1.0 mm Defect tracking (black dot), .8 mm Defect tracking (finger print), 65 µm Defect tracking (warped disc), -1.0 mm Defect tracking (eccentric disc), 210 µm Test Conditions Track 6, 6 sec. Track 9, 8 sec. Track 13, 10 sec. First and last track, 6 sec. First and last track, 6 sec.

27

TEST PROCEDURES

PCB 178335

PCB 199827

PCB 250736 Figure 5. Tuner Alignment Locations 28

REMOTE CONTROL ALIGNMENT
1. Remote Control Tuning 1.1 Connect TP48A (BATT +) to TP47. 1.2 Connect TP48A (BAT +) to L1 (AM MOD). 1.3 Connect an oscilloscope probe to TP22. Connect the scope ground near TP22. Note: A x10 probe is recommended. 1.4 Rotating C14 360 degrees, you should see two points where the signal peaks. Adjust C14 until the output at TP22 is peaked ( 6Vpp). It doesn't matter which peak you tune to. 1.5 TP19 should be 3 Vpp. TP20 should be 1 Vpp.

Figure 6. RC-20 Tuning Locations

29

ALIGNMENT PROCEDURES
Note: The CD changer must be placed into a CD-20 music center for the following procedures. The CD changer cannot be operated by itself. Equipment Needed 1. CD-20 Alignment Fixture (P/N: 191749) 2. Oscilloscope 3. DC Voltmeter 4. Test CD (A·Bex TCD-784) or equivalent. Note: Remove the solder from the location ATSC before performing any alignments. Perform these procedures in exact order! 1. FE Bias Alignment 1.1 Connect the power pack to the CD-20 and leave the CD-20 in the OFF mode. 1.2 Connect a DC voltmeter to TP824 (FE out) and TP704 (1/2 Vcc). See Figure 1.
Sled
Changer PCB

TP704

DC Voltmeter

CN902

_

+

ATSC

PT824

TP824

Figure 1. FE Bias Alignment
Changer PCB

TP705

CN903

1.3 Adjust the potentiometer PT824 until the meter reads < 10mVdc. 2. Tracking Balance Alignment 2.1 Insert the CD A·Bex TCD-784 and play track number seven. 2.2 Connect TP601 (TEST) to TP705 (GND). See Figure 2.

Track PT823 TP822

CN902

TP601

TP704

Oscilloscope

_

+

Figure 2. Tracking Balance Alignment 2.3 Remove the solder from the points labeled SLED and then TRACK.
Changer PCB

2.4 Connect an oscilloscope to TP822 (+) and TP704 (-). 2.5 Adjust PT823 (T.BAL) until the wave form is symmetrical about 0VDC, V1=V2. See Figure 5. 2.6 After the adjustment is done, solder the points labeled TRACK and SLED. Remove the connection from TP601 (TEST) to TP705 (GRN).

TP701 TP704
CN902

CN903

V+

GND

CD-A

X

TP823
CN903

1/2 V CC

CD-B

SCOPE

Y

PT821

FE TP824

,, ,,

F 1.75kHz

CD20 ALIGNMENT FIXTURE
POWER

T 2.15kHz

Figure 3. Focus Gain Alignment

30

ALIGNMENT PROCEDURES
3. Focus Gain Alignment 3.1 Unplug the power pack from the CD-20 5. Alignment Completion. 3.2 Remove the solder from the point labeled FE and connect the CD-20 alignment fixture as shown in Figure 3. 3.3 Turn the CD-20 on and play track number one of the A·Bex CD TCD-784.
Changer PCB

4.7 After the adjustment is complete, solder the point labeled TE.

5.1 Solder the point labeled ATSC. 5.2 Perform test procedure 1.

3.4 Switch the CD-20 alignment fixture's oscillator to 1.75 kHz. 3.5 Set the oscilloscope to the X-Y mode and connect CH2 of the oscilloscope to the "X" input and CH1 to the "Y" input of the alignment fixture. 3.6 Adjust PT821 (F. GAIN) for the best circle as viewed on the oscilloscope. See Figure 6. 3.7 After the adjustment is complete, solder the point labeled FE. 4. Tracking Gain Alignment
0V

TP701 TP704
CN902

V+

GND

CD-A

TP821 TE TP822 PT822
CN903
1/2 V CC CD-B

X

SCOPE

Y

,, ,,

F 1.75kHz

CD20 ALIGNMENT FIXTURE
POWER

T 2.15kHz

Figure 4. Tracking Gain Alignment

V1 V1=V2 V2

4.1 Unplug the power pack from the unit. 4.2 Remove the solder from the point labeled TE and connect the alignment fixture as shown in Figure 4. 4.3 Plug the CD-20 in and play track number 1 of the A·Bex CD TCD-784. 4.4 Switch the CD-20 alignment fixture's oscillator to 2.15 kHz. 4.5 Set the oscilloscope to the X-Y mode. Connect CH2 of the oscilloscope to the "X" input and CH1 to the "Y" input of the alignment fixture. 4.6 Adjust PT822 (T. GAIN) for the best circle as viewed on the oscilloscope. See Figure 6.

Figure 5. Symmetrical Waveform

Oscilloscope

Figure 6. X-Y Mode Output 10mV/ Division

31

PART LIST NOTES
1. This part is not normally available from Customer Service. Approval from the Field Service Manager is required before ordering. 2. The individual parts located on the PCBs are listed in the Electrical Parts Lists.

3. This part is critical for safety purposes. Failure to use a substitute replacement with the same safety characteristics as the recommended replacement part might create shock, fire and or other hazards. 4. The PCB assembly 199831-101C has a change to the AM circuit and uses a new AM antenna part number 199824-002. The PCB assembly 250737-101C has a change to the FM circuit in addition to the AM changes on the 199831-101C PCB. When replacing an older PCB assembly with either one of the PCBs (199831-101C, 250737-101C) the new AM antenna part number 199824-002 must be used with the new PCB assemblies. 5. These parts are not used on the 250737-101C PCB assembly. 6. This part is used on the 178335 PCB only. The 178335 PCB is the original PCB used on the CD-20. Most of the parts listed are common to all of the PCB variants. 7. This part is used on the European variant. 8. This part is used on the Japan variant. 9. This part is used on the Dual voltage variant. 10. The PCB part numbers 178349-101C and 199831-101C are no longer available. They have been replaced by PCB part number 250737-101C. When ordering a new PCB assembly, use part number 250737-101C and order the new AM antenna, part number 199842-002. Due to design changes in the Am section of the PCB 250737-101C it is important to use the new AM antenna, part number 199824-002, for proper impedance matching.

32

MAIN PART LIST
Item Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ------------------------U301 U301 U301 U301 U301 VFD VFD400 RR100 RR100 RR100 (Refer to Figure 7) Description COVER, TOP SCREW, TAPP, 6-13 X .875, PAN, XREC SUPERSTRUCTURE PCB, ASSEMBLY BASE ASSY SPRING, MOUNTING, CD-MECH CONSOLE, CONTROL BUTTON TREE SHIELD, BUTTON, ESD LENS DOOR ASSY. BEZEL, CHANGER CLIP, SPRING ADAPTER, MOUNTING, RIGHT GROMMET, MOUNTING CD MECHANISM ADAPTER, MOUNTING, LEFT BUTTON, EJECT VIEWSHIELD CLIP,SPRING, U TYPE SPRING, DOOR RETURN SCREW, #4-24, HI-LO, PAN, HD. TAPE, EMI TRACE SCREW, THUMB, SHIPP'G, CD MECH CLIP, GROUNDING CLIP, CHRISTMAS TREE TAPE, FOAM, ADH BACKED, W/LINER TAPE, TRANSFER (3M F9465PC) TAPE, FOAM TAPE, FOAM TUNER, SHIELDED, EURO TUNER, SHIELDED TUNER, FM, 88.5 TO 108 MHz TUNER, EURO TUNER, JAPAN BRACKET, VFD DISPLAY DISPLAY, VFD. RECEIVER, RF REMOTE, 27.145 MHZ RECEIVER, RF REMOTE, 27.145 MHZ RECEIVER, RF REMOTE, 47.280 MHZ Part Number 180038 187426-14 182311 or 250257 271911-101CK 183889-001 184041 178211 178339 180035 178208 180037 178210 199801 187576 178919 271835-001K 187577 197922 181090 178173-01 178340 184042-04 179277 198583 183893 179278 179265-06 183301-25100 179265-01 179265-02 179270 181081 251054 184589 188466-001 178922 179281 148588 191401-001 193053-001 Q t y . Note 1 3 1 1 1 4 1 1 1 1 1 1 4 1 4 1 1 1 1 1 1 2 1 3 1 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1,4, 10

5, 7, 9 5 7 8 5 7, 9

33

1

x3

2

2 x3

3 4

x4

6 5

6 x4

11 7 8 9

10

Figure 7. CD-20 Exploded View 34

CD MECHANISM PART LIST
(Refer to Figure 8) Item Number 1 2 3 4 5 6 7 8 9 10 11 A1 A104 A153 A228 A232 CN906 Description Assy, Base Top Comp. Assy, Base Center Comp. Assy, Bracket CD-CH Comp. Assy, Chassis CD Comp. Assy, Base Rear Comp. Assy, Shaft EV Comp. Assy, Base Front Comp. Assy, Frame EV Comp. Assy, Base Side Comp. Assy, Chassis Mount Comp. Assy, Bracket Loading Comp. FPC PIC Assy, FPC Elevator FPC Lift Spring Tension DL FPC Loading Wire Assy, 8P, 555mm Assy, PCB-W, Main Part Number 189092 189108 189159 189199 189155 189160 189193 189149 189112 189157 189156 189154 189161 189153 189144 189152 189162 189163 Note

2 1

Note: 1. This is the complete CD changer mechanism PCB. 2. This part is connected to the CD changer mechanism's PCB. Note: The table above lists all the parts that are available for the CD changer mechanism portion of the CD-20. The part numbers that are not proceeded by a letter represent an assembly that is outlined in Figure 8. Part numbers that are preceded by a letter represent individual parts called out in Figure 8.

35

Figure 8. CD Mechanism Exploded View 36

ELECTRICAL PART LIST
Resistors Reference Designator R1 R2 R11 R12 R14 R14 R18 R19 R22 R23 R24 R25 R26 R27 R100 R101 R102 R103 R104 R105 R108 R110 R111 R112 R113 R116 R117 R118 R119 R120 R121 R121 R122 R123 R127 R128 R129 R130 R131 R132 R133 R134 R135 R136 R137 R138 R139 R140 R141 R142 R143 R144 R145 R146 Description 82 OHM, 2512, 1W, 5% 7.5 OHM, 2512, 1W, 5% 130 OHM, 2512, 1W, 5% 910 OHM, 1206, 1/8W, 5% 2.0K, 2512, 1W, 5% 2.7K, 2512, 1W, 5% 330 OHM, 0805, 1/10W, 5% 330 OHM, 0805, 1/10W, 5% 2.2K, 0805, 1/10W, 5% 220 OHM, 1206, 1/8W, 5% 220 OHM, 1206, 1/8W, 5% 4.7K, 0805, 1/10W, 5% 910 OHM, 1206, 1/8W, 5% 10.0K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 1.00K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 1.00K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 39 OHM, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 15 OHM, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 15 OHM, 0805, 1/10W, 5% 750 OHM, 0805, 1/10W, 1% 15 OHM, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 3.90K, 0805, 1/10W, 5% 10 OHM, 0805, 1/10W, 5% 2.2K, 0805, 1/10W, 5% 750 OHM, 0805, 1/10W, 1% 3.90K, 0805, 1/10W, 5% 10 OHM, 0805, 1/10W, 5% 2.2K, 0805, 1/10W, 5% 330 OHM, 0805, 1/10W, 5% 330 OHM, 0805, 1/10W, 5% 51.1K, 0805, 1/10W, 0.1% 220 OHM, 0805, 1/10W, 5% 16.9K, 0805, 1/10W, 0.1% 51.1K, 0805, 1/10W, 0.1% 16.9K, 0805, 1/10W, 0.1% 37 Part Number 181895-82R0 181895-7R5 181895-1300 124895-9115 181895-2001 181895-2701 133626-3315 133626-3315 133626-2225 124895-2215 124895-2215 133626-4725 124895-9115 133626-1035 133625-1001 133625-1003 133625-1001 133625-1003 133625-1001 133625-1003 133625-1500 133625-1500 133625-1003 133625-1500 133625-1003 133625-1500 133625-1003 133625-1500 133625-1003 133626-3905 133626-1025 133626-1035 133626-1025 133626-1505 133626-1025 133626-1505 133625-7500 133626-1505 133626-4725 133626-4725 133626-3925 133626-1005 133626-2225 133625-7500 133626-3925 133626-1005 133626-2225 133626-3315 133626-3315 181896-5112 133626-2215 181896-1692 181896-5112 181896-1692 Note 6 6

6 6

ELECTRICAL PART LIST
Resistors (continued) Reference Designator R147 R148 R152 R161 R162 R163 R164 R165 R166 R200 R201 R202 R203 R204 R205 R208 R210 R211 R212 R213 R216 R217 R218 R219 R242 R243 R244 R252 R262 R263 R264 R300 R301 R302 R303 R304 R305 R309 R311 R312 R313 R314 R314 R315 R316 R317 R318 R319 R320 R321 R321 R322 R323 R324 Description 220 OHM, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 100K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 330 OHM, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 1.00K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 1.00K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 150 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 51.1K, 0805, 1/10W, 0.1% 220 OHM, 0805, 1/10W, 5% 16.9K, 0805, 1/10W, 0.1% 4.7K, 0805, 1/10W, 5% 100K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 5.6K, 0805, 1/10W, 5% 24K, 0805, 1/10W, 5% 10 OHM, 0805, 1/10W, 5% 5.6K, 0805, 1/10W, 5% 2.2K, 0805, 1/10W, 5% 24K, 0805, 1/10W, 5% 2.2K, 0805, 1/10W, 5% 22K, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 10 OHM, 0805, 1/10W, 5% 100 OHM, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 1.60K, 0805, 1/10W, 5% 620 OHM, 0805, 1/10W, 5% 22 OHM, 0805, 1/10W, 5% 9.1K, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 47.0K, 0805, 1/10W, 5% 1.2K, 0805, 1/10W, 5% 33 OHM, 1206, 1/8W, 5% 3.3K, 0805, 1/10W, 5% 38 Part Number 133626-2215 133626-1035 133626-4725 133625-1003 133625-1003 133625-1003 133625-1003 133625-1003 133626-3315 133625-1001 133625-1003 133625-1001 133625-1003 133625-1001 133625-1003 133625-1500 133625-1500 133625-1003 133625-1500 133625-1003 133625-1500 133625-1003 133625-1500 133625-1003 181896-5112 133626-2215 181896-1692 133626-4725 133625-1003 133625-1003 133625-1003 133626-5625 133626-2435 133626-1005 133626-5625 133626-2225 133626-2435 133626-2225 133626-2235 133626-4725 133626-1035 133626-1005 133626-1015 133626-4725 133626-1025 133626-1625 133626-6215 133626-2205 133626-9125 133626-4725 133626-4735 133626-1225 124895-3305 133626-3325 Note

5

6

ELECTRICAL PART LIST
Resistors (continued) Reference Designator R325 R326 R326 R328 R329 R330 R330 R331 R332 R333 R334 R334 R335 R335 R336 R336 R336 R337 R337 R338 R338 R339 R339 R340 R341 R341 R342 R343 R344 R346 R347 R348 R348 R349 R350 R351 R352 R353 R353 R354 R355 R357 R359 R360 R360 R361 R361 R362 R363 R401 R402 R403 R404 R405 Description 2.7K, 0805, 1/10W, 5% 8.2K, 0805, 1/10W, 5% 3.09K, 0805, 1/10W, 1% 12K, 0805, 1/10W, 5% 5.11K, 0805, 1/10W, 1% 10 OHM, 0805, 1/10W, 5% 51 OHM, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 120 OHM, 0805, 1/10W, 5% 330 OHM, 0805, 1/10W, 5% 2.32K, 0805, 1/10W, 1% 18.0K, 0805, 1/10W, 5% 499 OHM, 0805, 1/10W, 1% 390 OHM, 0805, 1/10W, 5% 560 OHM, 0805, 1/10W, 5% 2.32K, 0805, 1/10W, 1% 330 OHM, 0805, 1/10W, 5% 499 OHM, 0805, 1/10W, 1% 22K, 0805, 1/10W, 5% 330 OHM, 0805, 1/10W, 5% 330 OHM, 0805, 1/10W, 5% 2.32K, 0805, 1/10W, 1% 18.0K, 0805, 1/10W, 5% 390 OHM, 0805, 1/10W, 5% 560 OHM, 0805, 1/10W, 5% 330 OHM, 0805, 1/10W, 5% 22K, 0805, 1/10W, 5% 1.05K, 0805, 1/10W, 1% 4.7K, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 5K OHM, POT, RTRY, 30%, 1/2W 20K OHM, POT, RTRY, 30%, 1/2W 10K OHM, POT, RTRY, 30%, 1/2W 1.00K, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 47.0K, 0805, 1/10W, 5% 10.0K, 0805,1/10W, 5% 6.80K, 0805, 1/10W, 5% 10.0K, 0805,1/10W, 5% 4.02K, 0805, 1/10W, 1% 100 OHM, 0805, 1/10W, 5% 2.32K, 0805, 1/10W, 1% 100 OHM, 0805, 1/10W, 5% 330 OHM, 0805, 1/10W, 5% 100 OHM, 0805, 1/10W, 5% 100 OHM, 0805, 1/10W, 5% 100 OHM, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 39 Part Number 133626-2725 133626-8225 133625-3091 133626-1235 133625-5111 133626-1005 133626-5105 133626-1035 133626-1025 133626-1215 133626-3325 133625-2321 133626-1835 133625-4990 133626-3915 133626-5615 133625-2321 133626-3325 133625-4990 133626-2235 133626-3315 133626-3325 133625-2321 133626-1835 133626-3915 133626-5615 133626-3325 133626-2235 133625-1051 133626-4725 133626-4725 177494-203 177494-502 177494-103 133626-1025 133626-4725 133626-1025 133626-4725 133626-4735 133626-1035 133626-6825 133626-1035 133625-4021 133626-1015 133625-2321 133626-1015 133626-3315 133626-1015 133626-1015 133626-1015 133626-1035 133626-1035 133626-1025 133626-1025 Note 5 5

5 5 5 5 6 5 5 5 5 5 6 5 5 5

6 6

6

5 5 5 5 5

ELECTRICAL PART LIST
Resistors (continued) Reference Designator R406 R408 R409 R410 R411 R412 R413 R414 R415 R416 R417 R418 R419 R420 R421 R422 R423 R424 R425 R426 R428 R429 R430 R431 R432 R433 R434 R435 R436 R436 R437 R438 R439 R439 R440 R440 R441 R441 R442 R443 R444 R445 R446 R447 R447 R447 R448 R449 R450 R451 R452 R453 R454 R455 Description 1.00K, 0805, 1/10W, 5% 100 OHM, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 2.7 OHM, 0805, 1/10W, 5% 100 OHM, 0805, 1/10W, 5% 100 OHM, 0805, 1/10W, 5% 2.7 OHM, 0805, 1/10W, 5% 2.7 OHM, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 43.2K, 0805, 1/10W, 1% 43.2K, 0805, 1/10W, 1% 10.0K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 1.00K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 10.0K, 0805, 1/10W, 5% 43.2K, 0805, 1/10W, 1% 511 OHM, 0805, 1/10W, 1% 511 OHM, 0805, 1/10W, 1% 100K, 0805, 1/10W, 1% 33.0K, 0805, 1/10W, 5% 4.7K, 0805, 1/10W, 5% 33K, 0805, 1/10W, 5% 30K, 0805, 1/10W, 5% 10.0K, 0805,