38758437 bose av28 service manual

5/28/2018 38758437 BOSE AV28 Service Manual

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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 SERVICE CENTER OR OWNER OF THE

BOSE PRODUCT, AND SHALL NOT BE REPRODUCED OR USED

FOR ANY OTHER PURPOSE.

Software Update Information

The software in the AV28 Media center can be updated using a software update CD available from

Boseservice. Refer to procedure 2 on page 70, Console-Key Special Function Features, to

determine the software version of the unit. Contact Bose Service or refer to the Bose service

extranet site for information regarding the latest software revision; click on Lifestyle music centers

and then AV28 media center. http://serviceops.bose.com

Contents

Safety Information ............................................................................................................................2

Electrostatic Discharge Sensitive (ESDS) Device Handling .........................................................2

Specifications ................................................................................................................................ 3-5

Theory of Operation ................................................................................................................... 6-28

Disassembly/Assembly ............................................................................................................ 29-30Setting-up a Computer to Issue TAP Commands ........................................................................31

Issuing TAP Commands to the AV28 media center .....................................................................32

General Test Procedure Notes .......................................................................................................32

Functional/Performance Verification Tests ............................................................................. 33-34

Adjustment/Performance Verification Procedures ................................................................ 35-37

Figure 1. AM Test Setup ....................................................................................................................35

Figure 2. Tap Test Cable Part Number 264565 ..................................................................................38

Part List Notes.................................................................................................................................38

Main Part List...................................................................................................................................39

Figure 3. Exploded View ....................................................................................................................40

Main PCB 260318-0 Electrical Part List ................................................................................... 41-55

Tuner PCB 260322-1 Electrical Part List ................................................................................. 56-60Head Unit Packaging Part List .......................................................................................................61

Figure 4. Console Packaging ............................................................................................................61

Figure 6. Laser Current Measurement Point......................................................................................62

Figure 5. DVD Player Rear Panel ......................................................................................................62

Laser Current Measurement ..........................................................................................................62

Integrated Circuit Diagrams..................................................................................................... 63-67

Changing House Codes .................................................................................................................68

Figure 7. House Code Settings .........................................................................................................68

Zone 2 Operation ............................................................................................................................69

Figure 8. Zone 2 Remote Control Switch Setting ..............................................................................69

Console-Key Special Function Features ......................................................................................70Click here to go to the revsion history page.

This manual is to be used to service early version AV28 media centers.


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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 accept-

ably 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) 6500 IEC

60065 paragraph 9.1.1. With the unit switch first in the ON position and then in 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 2 and 5.2 Megohms. When testing 3 wire products, the resistance measured to

the product enclosure should be between 2 and infinite Meg ohms. Also, the resistance measured

to exposed output/input connectors should be between 4 and infinite Meg ohms. When testing 2

wire products, the resistance measured to exposed output/input connectors should be between 4

and infinite Meg ohms. If it is not within the limits specified, there is the possibility of a shock haz-ard, and the unit must be repaired and rechecked before it is RETURNED TO THE CUSTOMER.

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 unpro-

tected devices into materials such as plastic, polystyrene foam, clear plastic bags, bubble wrap or

plastic trays.

SAFETY INFORMATION


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Specifications

Physical Description:

Dimensions: 15.8" W x 11.0" D x 3.5" H (40.1 x 27.9 x 8.9 cm)

Weight: 8.2 lbs. (3.7 kg)

Cover: Aluminum

Base: Molded plastic

Display: Vacuum fluorescent

Inputs:

TAPE: 2 Vrms, maximum

AUX: 2 Vrms, maximum

VCR: 2 Vrms, maximum

TV: 2 Vrms, maximum

Digital: S/PDIF (1 each for TV, VCR, TAPE, and AUX)

Composite video: NTSC or PAL format 1Vpp with sync 75 Ohm

S-Video: Luminance 1Vpp, chrominance 0.3Vpp

Component video: NTSC or PAL 1Vppwith sync on Y

Optical input: S/PDIF digital, mapped to input

FM antenna: 75 Ohm

AM antenna: 12uH

TV sensor: NTSC/PAL/HDTV/480p compatible

Power: 33 Vdc, 2.1mm jack, provided by DCS91 power packSerial data port: 3.5mm miniature stereo jack, data in/out

Remote control receiver: RF or IR, user selectable

Outputs:

Speaker Zone 1: S/PDIF and variable analog

Speaker Zone 2: S/PDIF and variable analog

Record L and R: Fixed audio

Record digital: S/PDIF and Optical

Optical output: S/PDIF, -15 to -21 dBm

Composite video: NTSC or PAL 1Vppwith sync 75 Ohm

S-Video: Luminance 1Vpp, Chrominance 0.3Vpp

IR: Controls other manufacturer's IR operated devices,universal method

FM Tuner:

Tuning range: 87.7 MHz-107.9 MHz

De-emphasis: 75 usec

Channel spacing: 200 kHz

Sensitivity, mono usable: 13 dBf

Stereo, 50 dB quieting: 38 dBf

Signal-to-noise @ 65 dBf: Mono: 74 dBf, Stereo: 70 dBf

Noise ratio @ 65 dBf: Mono: 85, Stereo: 85

Harmonic distortion, 1 kHz, @ 65dBf Mono: 0.3%, Stereo: 0.4%

Capture ratio @ 45 dBf: 2.0 dB

AM rejection @ 45 dBf: 60 dB

Adjacent channel selectivity, 200 kHz,

for both channels, @ 45 dBf:

13 dB

Alternate channel selectivity, 400 kHz,for both channels, @ 45 dBF:

70 dB

Image rejection: 45 dB

RF inter-modulation: 65 dB

Sub-carrier product rejection @ 65 dBf: 55 dB

Frequency response 30 Hz-15 kHz: +1.0 dB

Stereo channel separation @ 1 kHz: 35 dB

Auto stop level (seek): 30 dBf

Mono/Stereo threshold: 40 dBf


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Specifications

AM Tuner:

Channel spacing: 10 kHz

Test Parameter Condition 530-550kHz

560-590kHz

600-700kHz

710-950kHz

960-1400kHz

1410-1610kHz

1620-1710kHz

Nominal 55 52 50 49 48 47 47

AmbientLimit

61 57 55 55 53 52 52

UsableSensitivity1,dBuV/m

EnvironmentalLimit

67 63 61 60 59 58 58

Nominal 26 26 27 23 23 25 22AdjacentChannelSelectivity

2, dB

Ambient Limit 21 21 22 18 18 20 17

Nominal 30 30 30 30 30 29 27AlternateChannelSelectivity

2, dB

Ambient Limit 25 25 25 25 25 24 22

Nominal 35 37 40 40 40 40 40ImageRejection

Ratio, dB

Ambient Limit 30 32 35 35 35 35 35

Nominal 50 50 50 50 50 50 50

Ambient Limit 45 45 45 45 45 45 45

Signal to NoiseRatio, dB

EnvironmentalLimit

40 40 40 40 40 40 40

Nominal 0.6 0.6 0.6 0.6 0.6 0.6 0.6

AmbientLimit

1.4 1.4 1.4 1.4 1.4 1.4 1.4

Distortion, %

EnvironmentalLimit

2.0 2.0 2.0 2.0 2.0 2.0 2.0

Nominal -3 -3 -3 -3 -3 -3 -3FrequencyResponse, dB@ 220 Hz, 2.0

kHz

Ambient Limit -6 -6 -6 -6 -6 -6 -6

Auto StopLevel, dBuV/m

70 7 65 7 63 7 60 7 54 7 48 7 48 7

Single disc CD/DVD:

Supported formats: DVD video, Audio CD, CD-R, CD-R/W, MP3 CD

CD performance:

Parameter Nominal Limit Test Disc

Defect Tracking (void) 1.0 mm 0.8 mm ABEX test disc TCD-725A

Defect Tracking (black dot) 1.0 mm 0.8 mm ABEX test disc TCD-725R

Defect Tracking (scratch) 1.6 mm 1.0 mm ABEX test disc TCD-721 R

Defect Tracking(finger print)

75 mm 65 mm ABEX test disc TCD-725R

Defect Tracking(warped disc)

1.0 mm 0.7 mm ABEX test disc TCD-732RA

Defect Tracking(eccentric disc)

210 mm 140 mm ABEX test disc TCD-714R

Cueing Time 2 sec 3 sec Phillips TS4, tracks 1-15


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Specifications

Analog Inputs:

Input level: Full scale output; 2 Vrms maximum, 200 mVrms

Input impedance: 33 k

Input coupling: AC coupled

Analog Outputs:

Output level: 2 Vrms

Output level from FM: 0.6 Vrms

Output level from AM: 0.4 Vrms

Source impedance @ 1 kHz: 220 Ohms

Load impedance: 10 k, 2 k minimum

Output coupling: AC coupled

Headphone Jack:

Connector: Mini stereo jack

Output level: 31 mW at THD


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Theory of Operation

PCB Assembly P/N

Main PCB 260318-0

IR PCB Part of 260318-0

Headphone PCB Part of 260318-0

Tuner PCB 260322-1

Keypad PCB 254141

1.0 Overview

The AV28 media center is a self-contained DVD/CD/MP3 disc player with an AM/FM tuner for use

with Bosepowered speaker systems. In addition to the two internal sources (DVD/CD and AM/

FM tuner), it allows playing up to four external audio sources: TV, VCR, AUX, and TAPE. A 27MHz,

one-way RF remote control operates the unit without line-of-sight restriction; provisions for infrared

remote control of the media center also exist. An integrated IR Blaster allows limited control ofother manufacturers equipment (TVs, VCRs and Cable/Satellite Set-Top boxes). The AV28 media

center has two independent audio output zones, accessible through circular DIN connectors in the

back of the product.

The AV28 media center contains five PCBs:

There are some components shown on schematics whose reference designators end in NV;

these components are not loaded by manufacturing, but their pads exist on the PCB.

Block Diagram

U1

CS9800

DVD Decoder IC

Flash

VFD

DVD ROM

Drive

IR Blaster

Board

TV Power

Dongle

Power

Supply

Synch

IR

Receiver

Console

Buttons

UEI

Blaster IC RF Remote

XCVR

Audio Path Power

Supply

ETAP

ATAPI

CCB Bus

Power Fail

DRAM

Video Path

AM / FM

Tuner


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Theory of Operation

Voltage Type PCB Location

(schematic page)

Input Outputs

+33 Linear Power Pack 120VAC +12V, +5.1V, +3.3V+12 Switching Tuner (3) V_RAW DVD drive, VFD, +10V

+10 Linear Tuner (3) +12 Tuner, Transceiver, Audio path, +8V

+8 Linear Main (9) +10 Video circuits

+5.1 Switching Main (9) V_RAW DVD drive, Audio path, +3.3

+3.3 Switching Main (9) V_RAW Flash, DRAM, U1 I/O & core, misc. logic

+2.5 Linear Main (9) +3.3 U1 PLL circuits

2.0 Power Supply Electronics

2.1 Architecture

V_RAW is provided to the console by an external power pack and is approximately 33VDC. The

power pack is a linear transformer. In addition to the usual large capacitor and full-bridge diode

rectifier, a PTC thermistor (effectively a reset-able fuse) is contained in the power pack to protect

the unit under fault conditions. V_RAW enters the console on the tuner PCB, passes through an

NTC thermistor to eliminate power supply startup surges, and is fed to the +12V supply and theflat-flex cable, which feeds it to the +5.1V and +3.3V supplies on the Main PCB.

Power Supply Block Diagram

2.2 Switching Power Supplies

See SD254135 sheet 9 and SD256131 sheet 3 for the power supply circuits.

The switching power supplies are ST L4973D3.3 regulator ICs (U802 and U803 on the Main PCB,

and U301 on the Tuner PCB). The power supplies are designed as step-down Buck converters.

The voltage fed back to the chip on pin 13 determines the output voltage; the chips control circuitrywill work to keep this voltage at +3.3V. The +5.1V and +12V supplies use resistor divide-down

networks to obtain the +3.3V feedback voltage.

The reference designators discussed in this section correspond to the +12V regulator on the tuner

board; the designs of the +5.1V and +3.3V regulators are nearly identical. A number of additional

components exist to provide filtering functions.

+33VDCS

9X

Linear

+12V

SMPS

+5.1V

SMPS

+3.3V

SMPS

+2.5V

Linear

+10V

Linear

+8V

Linear

AC linevoltage

from wall


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Theory of Operation

2.3 Supply Synchronization Generator

To limit radiated noise, all three switching supplies (12V, 5V and 3.3V) are synchronized to the

same control frequency. This frequency is varied by U1, as needed, to keep noise out of the AM

tuner.

U805 is a 74HC592 8-bit binary counter IC with an input register. An 11.2896 MHz clock signal isfed to the counter clock (CCK) pin, and the chip counts on positive edges of this signal. Inputs A

through H are loaded to the register on positive edges of the register clock (RCK) signal, and the

register outputs are loaded to the counter when the active-low counter load (/CLOAD) is asserted.

These two signals are driven by the chips own active-low ripple carryout (/RCO), which is also the

output to the level shifter circuit. The active-low counter clock enable (/CCKEN) is pulled low by a

100 Ohm resistor, and the active-low asynchronous counter clear (/CCLR) is tied to the Main

PCBs hardware reset line. The /RCO output is fed to a level shifter circuit (Q801 and Q804).

The synchronization clock is fed to all three switching power supply regulators in the console. The

clock frequency will be either 98.1704 kHz or 101.7081 kHz, depending on the state of

SUPPLY_FREQ_SEL, driven by U1. U1 picks the state based on AM tuner frequency.

2.4 Power Fail Detection

Q802 and Q803 detect a power failure by asserting the active-low /POWER_FAIL signal when the

console input voltage V_RAW falls below a given threshold (equivalent to an AC line voltage of

about 75 VACRMS). This signal is fed to U1 as an interrupt so the micro can perform some shut-

down functions before it is held in reset; see section 3.1.2 for additional information.

2.5 Grounding

R321 on the Tuner PCB connects PGND (the ground provided to the product by the power pack)

and GND (tuner signal ground). The power supply ground on the Main PCB is connected to GNDonly at C832 and C828.

Additional signal ground connections between the Main and Tuner PCBs and between the PCBs

and the conductive paint on the plastics are made by conductive gasket material attached to the

plastic cover and base.

IC Pin Components Connected Pin Function

1 R301, C302, C303 Sets switching frequency (when not controlled

externally)

10 C308 Drives internal D-MOS

11 R322 Inhibits supply

12 R302, C305, C307 Lead-lag filter for compensation loop

13 R304, R305 Voltage feedback for control18 C304 +5.1V for external reference

19 C306 Sets supply soft-start time constant

20 None Supply frequency switching synchronization(see note)


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Theory of Operation

2.6 Troubleshooting

Verifying functionality of the power supply system by measuring the DC levels on each supply

(including the power pack) is sufficient for basic troubleshooting.

If power supply problems are suspected, or if DC levels on the supplies are incorrect, evaluate

and correct these parameters with no power applied:

Check continuity between J104 and pin 8 of each supply.

Measure the resistance of R321 on the Tuner PCB.

Measure the resistance of feedback resistors (R304 and R305 in the +12V supply) in each supply.

Verify that no supply voltage output is shorted to ground.

3.0 Control Electronics

The majority of the control electronics are located on the Main PCB, the notable exceptions being

the Infrared Blaster diodes and receiver module (located on an auxiliary PCB under the DVD-ROM

drive tray) and the RF transceiver circuitry (located on the Tuner PCB).

3.1 Processor

U1 is a CS98000 DVD decoder IC that also functions as the media centers main processor.

U1 contains two built-in 32-bit RISC processors, a DSP core, a memory interface which supports

SDRAM and FLASH ROM, an ATAPI interface, a DMA controller, an MPEG video decoder, on-

board data and instruction caches, a digital video interface, digital audio processing, a general

purpose interface, and numerous general-purpose I/O.

One RISC processor in U1 (RISC0) manages the ATAPI interface to the DVD-ROM drive, and

handles all low-level details associated with playback/navigation of DVD and CD discs. RISC0sends standard ATAPI control commands to the drive and receives MPEG-compressed audio,

video, and control information back. It decodes the MPEG information from the DVD-ROM drive on

the ATAPI bus and stores the decoded video into SDRAM for later readout to the video interface. It

also oversees the onboard DSP core, as required, when decoding digital audio data, and sends it

out the digital audio interfaces.

The second RISC processor (RISC1) runs Bosesoftware that handles system control, as-

sembles VFD and On-Screen Display (OSD) information, and controls I/O functions including

reading the console buttons, receiving the RF and IR remote control commands, driving the OSD

and VFD display on the console, controlling the AM/FM tuner sub-circuit, and driving the IR blaster

controls.

Connections to U1 are made throughout SD254135.


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Theory of Operation

3.1.1 Processor Clock

U1 is clocked by a crystal inverter-oscillator whose nominal frequency is 27 MHz.

A 10KW resistor (R713) biases one gate of U701, a 74VHCU04 [high-speed, unbuffered] inverter.

The crystal in the inverters feedback path is designed for a 22pF load, achieved by the series

combination of the two 30pF load capacitors C704 and C707 and other stray capacitance in theinput gates of U1. R714 sets the pole in the oscillators loop response, and R715 buffers the output

between the oscillator and U1. See sheet 8 of SD254135.

After the signal is buffered by U1, the 27 MHz clock drives the video circuitry. Frequency accuracy

within 50ppm of this oscillator circuit is necessary for color video operation.

3.1.2 Processor Reset

U703 generates a 140ms reset pulse at power-on and any time the +3.3V supply dips below 2.93

volts (corresponding to an AC line voltage of about 40VACRMS. The pulse is buffered by two of

the gates of U701, a 74VHCU04 inverter, and distributed as active-low /RESET1. The reset signal

ensures reliable startup of U1 at power-up and after a brownout.

See the comments in section 2.4 regarding power-fail detection.

3.2 Memory

See sheet 1 of SD254135.

The U1 memory interface supports both SDRAM and flash memory of various sizes. Both memory

ICs are connected to the same bus, and a chip select chooses between the two devices. The type

of memory cycle that is run depends on which address space is needed.

3.2.1 FLASH

U2 is a 1-megaword by 16-bit Flash memory IC. FLASH memory is nonvolatile, meaning that its

stored data is not lost when the chip loses power. The FLASH is used to store all application

software for the product (including software to run on both of U1s RISC processors and its DSP).

This software is programmed into the FLASH by Manufacturing during In-Circuit Test. The FLASH

also stores nonvolatile user parameters, such as AM/FM presets and OSD setup preferences.

U2 shares the memory address and data bus with U3, but its cycle is different from the SDRAM:

flash access is asynchronous and does not use a memory clock. Address (pins 1-9, 18-24, and

48) and chip select (pin 26) is presented to the chip, and data appears 1 access time later on the

data bus. The flash chip only supplies 16-bit data to U1; the other data bus lines are not driven

during flash access.

U2 can be programmed in-circuit by U1; this allows media center software updates in the field via

CD-ROM. During reprogramming, the new program is held in SDRAM (along with the operating

program) until checksum-verified, then written permanently to FLASH.


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Theory of Operation

3.2.2 SDRAM

U3 is a 2-megaword by 32-bit synchronous dynamic random access memory (SDRAM) IC. When

the media center powers-up, the application program from the FLASH is shadowed into and ex-

ecuted out of the SDRAM to improve speed. The SDRAM is also used to hold blocks of com-

pressed and decompressed audio and video data, as well as numerous variables and flags, as

required by the software.

For SDRAM accesses, a memory clock of about 100 MHz that synchronizes data access is sent

to the chip at pin 68. Data commands for accesses are coded in the /RAS and /CAS signals (pins

18 and 19), and data read/write selection is done by the /WE signal (pin 17). The address to be

written or read is given on the address bus (pins 25-27 and 60-66). The 32-bit data bus contains

the word to be written or read after the pipeline delay of the memory chip. The detailed operation of

the SDRAM is outside the scope of this document.

3.3 Remote control

3.3.1 RF Transceiver

See sheet 2 of SD256131.

The AV28 media center RF transceiver operates at 27.145 MHz using on-off keying (OOK). The

RF transceiver circuits are located on the Tuner PCB. The antenna for the RF transceiver system

is the DC power cord attached to J104; a 10mH inductor in the power pack facilitates transmission

and reception over the zip cord. The RF signal is capacitively coupled to the V_RAW line by C214.

3.3.1.1 Receiver

The remote control receiver module is an AM receiver; it takes the RF signal from the antenna line,

demodulates it, and outputs the received data to the data slicer circuit. U104, an LM393 dual

comparator, acts as a data slicer and outputs TTL-level signals for the received data waveform.The RF_DATA_RCV output line connects to U1 through J103.

3.3.1.2 Transmitter

The AV28 media center contains a transmitter for future bidirectional remote control operation.

Q202 and Y201 form a crystal oscillator that is powered when the XMIT/RCV_SEL line from U1 is

high. The output of the oscillator is fed to Q205, a Class-C RF amplifier. Data is sent on the trans-

mitter by way of the RF_DATA_XMIT line from U1, which powers the amplifier. The amplifiers

output is fed through a tank circuit and the filtering network.

3.3.1.3 Filtering network

Passive components on the V_RAW line provide filtering for the RF remote signal: L203, C218, and

C217 form a 27.145 MHz notch; L205, C219, and C216 form a 45.290 MHz (second harmonic of

27.145 MHz) notch. C222, C223, and C224 aid in limiting undesired radiated emissions. FB1 is a

ferrite bead designed to improve tuner performance by limiting radiated self-noise in the FM band.


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Theory of Operation

3.3.1.4 RF Remote Control

The RF remote control contains a similar transmitter to the one described in section 3.3.1.2. The

remotes DIP switch functions are as follows:

Switches 1-4: 4-bit House Code. All AV28 media centers are shipped set to respond to House

Code 0000 (switches 1-4 all down).

To change the House Code of an AV28 media center, do the following:

1.Turn it OFF using the ALL OFF button on the media center.

2.Press and hold the STORE button on the console.

3.While holding the STORE button, press any button on an RF remote set for the desired House

Code. When the AV28 receives this RF message, it will adopt the new House Code as its own.

Switches 5-6: 2-bit Zone Code. If switch 6 is up, the remote will control Zone 1. If switch 5 is up, the

remote will control Zone 2. If BOTH switches are up, the remote will control BOTH zones.

Switches 7-9: 3-bit Room Code. The AV28 is capable of controlling up to 7 speakers in each zone.

Each speaker has a 3-bit Room Code. Zone 1, Room A (000) is defined as the primary room (the

console buttons will also control this room), and is the Room Code set as a default on all LS28/35

bass module speakers shipped with the AV28. To control the media centers variable analog out-

puts, the RF remote control needs to be set for Room G (110).

3.3.2 Infrared Transceiver

The AV28 media center contains a built-in IR Blaster capable of sending control commands out the

black lens along the bottom front of the product to other manufacturers A/V equipment. Similarly,an IR receiver is built-in which allows the media center to be controlled by any IR remote control

capable of sending Bose AV28 control commands.

3.3.2.1 Infrared Blaster IC

The IR Blaster IC (U704) is an 8-bit microcontroller located on the main board, sold by UEI elec-

tronics. The IC is pre-programmed with an extensive set of IR control commands for a number of

other manufacturers devices. Devices able to be controlled are limited to TVs, VCRs, Cable Set-

Top Boxes and Satellite Set-Top Boxes. Over one hundred manufacturers are represented, cover-

ing the U.S./North American, European, South American and Asian markets. To enable sending IR

control commands, the user must select the desired Manufacturer and Device Codes from lists in

the OSD System Setup menus.

Additionally, the AV28 is capable of teaching an IR learning remote the commands required to

control the media center. When the user enables the Transmit IR function in the System Setup

OSD menu, the AV28 will automatically echo all received RF remote control messages out its IR

Blaster in Bose AV28 IR format. An IR learning remote can then be taught to control the AV28 by

holding it near the front of the media center as the user presses the desired RF buttons.


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Theory of Operation

3.3.2.2 Infrared Blaster Diodes

Four diodes located on the IR PCB transmit infrared messages to external A/V equipment. U704

provides the modulated data for the diodes; Q703 and Q706 supply the +5V drive voltage, and

R729 and R730 on the Main PCB limit the IR transmit current (setting the transmit brightness).

3.3.2.3 IR Emitter

For situations where the position of the AV28 does not allow its built-in IR Blaster signals to prop-

erly control an external product, a supplemental IR Emitter dongle can be plugged into the back of

the media center and pointed more directly at the equipment in question. This dongle is essentially

a combination cable and IR-transmitter diode, and plugs into the jack labeled IR Emitter (J704).

Q703/Q705 provide the +5V drive voltage for the dongle, and R739/R740 limit the drive current to

about 50mA.

3.3.2.4 Infrared Receiver Module

The IR PCB contains an infrared receiver module. This module allows the media center to becontrolled by any IR remote control capable of sending BoseAV28 IR commands (NOTE: Re-

ceive IR needs to be enabled via the System Setup menus in the OSD first, however). The Main

PCB supplies +5.1V to the module. The module performs light filtering functions, optical to electrical

conversion, demodulation about a 38-kHz carrier, and level shifting to provide TTL-level outputs to

U1. The plastic housing surrounding this area is translucent to infrared. Infrared control must be

enabled in the OSD to be functional.

3.3.2.5 Infrared Troubleshooting

During the Power-On Self-Test (POST) phase, the console attempts a query of the IR Blaster IC

and an infrared loopback test; TAP query and the console keypad provide access to test results.

If the IR Blaster IC query fails, concentrate troubleshooting efforts on U704 on the Main PCB.

Symptoms of successful queries to the IR Blaster IC and failed loopback tests require trouble-

shooting of the IR PCB. First, verify cable placement and integrity. Verify basic receiver module

functionality by injecting an infrared signal (for example, a Bose Wave Radio remote) and measur-

ing pin 3 of J1000 on an oscilloscope. To test basic transmitter functionality, verify diode conduction

and orientation, then issue TAP commands to control a Bose Wave Radio.

Troubleshooting customer complaints regarding control integration exceeds the scope of this

document.


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14

Theory of Operation

3.3.2.6 IR Key Codes

The following table describes the key codes capable of being generated by the built-in UEI Blaster

chip:

Note: No IR sent.

TV CBL SAT VCR

Key

Code#

Function Name T C S V

1 Power / Standby Power,Standby

Power,Standby

Power,Standby

Power,Standby

2 Digit 1 Digit 1 Digit 1 Digit 1 Digit 1







9 Digit 8 Digit 8 Digit 8 Digit 8 Digit 810 Digit 9 Digit 9 Digit 9 Digit 9 Digit 9


12 Enter Channel Enter Channel Enter Channel Enter Channel Enter

13 -/-- , / 10+ -/--, 10+ -/--, 10+ -/--, 10+ -/--, 10+

14 PreviousChannel

PreviousChannel

PreviousChannel

PreviousChannel

PreviousChannel

15 20+ 20+ 20+ 20+ 20+

16 Channel Up /Program Up

Channel Up Channel Up Channel Up Channel Up

17 Channel Down /Program Down

Channel Down Channel Down Channel Down Channel Down

18 TV/VIDEO TV/VIDEO A/B TV/DSS,TV/SAT

TV/VCR

19 Input ---- ---- ---- Input Select

20 Play ---- ---- ---- Play

21 Stop ---- ---- ---- Stop

22 Fast Forward ---- ---- ---- (Search)Forward

23 Rew ---- ---- ---- (Search)Reverse

24 Pause ---- ---- ---- Pause

25 Guide Guide Guide Guide ----

26 Exit Exit Exit Exit ----27 Select Select Select Select ----

28 Up Up Up Up ----

29 Down Down Down Down ----

30 Left Left Left Left ----

31 Right Right Right Right ----

32 Record ----- ----- ----- Record


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Theory of Operation

4.0 Audio Electronics

The AV28 is a 2-Zone audio system, meaning that users can simultaneously listen to one audio

source in one room and a second audio source in another. Therefore, much of the audio path

hardware is split into two sections: Zone 1 hardware and Zone 2 hardware.

Furthermore, the media center outputs each zones audio content in two different forms: analogand digital. The analog outputs are standard left/right, 2Vrms (max) signals similar to those found

on past Boseproducts. Some of these outputs are variable level, with volume control cells in

series with them. Other analog outputs are fixed level, and remain at the 2Vrms (max) level, re-

gardless of the users volume setting. Examples of variable outputs would be the headphone

outputs and the analog left/right signals on the Speaker Output mini-DIN connectors. The only fixed

analog outputs are the Record Out left and right signals. See the diagrams, below.

The digital outputs are serial digital audio data streams in S/PDIF format. These output streams

contain the same audio source material as their analog counterparts in each Zone, but the left/right

information has been digitized and combined into a single datastream. The S/PDIF outputs, how-

ever, may send either 2-channel (PCM) audio, or bursts of compressed multichannel audio (in AC-

3, AAC, MPEG-2, MP-3, or DTS formats). The amplitude information within the S/PDIF streams

never varies with volume level; instead, speakers receiving the streams will perform the volume

control function.

There are both analog and digital options for all AV28 audio inputs, as well. A simplified diagram of

the audio path would therefore be:

U303

CS4224

Z1 Codec w/

Volume Control

Internal Analog

Audio Sources

(Tuner, DVD 2-Channel

Mixdown)U201

TEA6422

ANALOG MUX

(Selects the desired

analog input

for each Zone)

Zone 1

Speaker Output(Variable)

Zone 2

Speaker Output

(Variable)

Zone 1

Headphone Output

Zone 1

Record Output

(Fixed)

External Analog

Audio Sources

(TV, VCR, AUX, Tape)

U403

CS4224

Z2 Codec w/

Volume Control

DVD-ROM

Playback

(DVD, CD)

U501

CS8415

S/PDIF MUX

(Selects the

desired

S/PDIF input)

Zone 1 Digital

S/PDIF Output

Zone 2 Digital

S/PDIF Output

External Digital

Audio Sources

(TV, VCR, AUX, Tape)

Record Digital

S/PDIF Output

U1

CS98K

DVD

DECODER

U306

CS8405

Z1 S/PDIF

XMTR

U406

CS8405

Z2 S/PDIF

XMTR

ATAPI

PORT


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16

Theory of Operation

Analog audio sources to be played in Zone 1 or Zone 2 are selected by U201, the TEA6422 analog

MUX IC. The chip has separate left/right output pairs for each zone, and is controlled by U1 via the

serial I2C interface. Its outputs are fed into the Zone1/Zone2 audio codecs (U303 and U304).

The codecs first digitize the analog signals using onboard 24-bit A/D (analog to digital) converters.

The digitized result (in I2S format) is then simultaneously fed out to the Zone1/Zone2 S/PDIF

transmitters (U306/U406) and back into the codecs. Once back in the codecs, signals are con-verted back to analog via 24-bit DACs (digital to analog converters), passed through onboard

volume control cells, then outputted once again as left/right signal pairs. U305 and U405 form

differential amplifiers that increase the codec audio outputs to a full-scale level of 2Vrms, and filter-

out unwanted high-frequency digital noise. The resulting analog signals feed the headphone out-

puts as well as the Zone 1 and Zone 2 speaker outputs. Volume control levels are set by U1 via

the I2C interface. Zone 1 signals pass through a set of mute transistors, Q300 through Q304,

which quiet the Zone 1 speaker outputs when the headphones are plugged-in.

The same I2S signals which feed the Zone 1 S/PDIF transmitter (U306) also feed U202, a CS4340

DAC. This DAC creates the fixed-level analog signals sent out the analog left/right Record Outputs.

A set of logic gates, U302, U304, U402 and U404 (74LCX157 Quad 2-Input Digital MUX chips) are

used to route I2S signals (consisting of a Data line, Master Clock, L/R Frame Clock and Bit Clock)

between the codecs and the S/PDIF transmitter chips. These digital MUX chips are controlled by

U1 using a set of individual logic lines (where a +3.3V level selects the B inputs, and a 0V level

selects the A inputs). These logic lines have various schematic names, and are connected to the

SELECT pin of each 74LCX157. These same chips route the digital audio signals from U1 (also in

I2S format), discussed next.

Digital audio input streams are selected by U501, the S/PDIF MUX chip, before being funneled into

U1, the CS98K DVD Decoder IC. In this way, the CS98Ks onboard DSP can decode the desired

stream if it happens to be in a compressed audio format (AAC, AC-3, MPEG-2, MP3, DTS or

MLP). U501 selects the desired stream based on I2

C commands from U1.

Streams played from discs in the DVD-ROM drive are clocked out of the CS98K at a sample rate

equal to the rate at which they were recorded. CD audio (CD-DA) discs all require a 44.1kHz

sample rate. Audio from DVD video discs typically requires a 48kHz sample rate, but may use

other rates. External streams received through the S/PDIF MUX will need to be clocked out of the

CS98K at a sample rate synchronous to the clock encoded into the stream (may be many different

rates). The CS98Ks AC-97 port is hard-wired to an external 44.1kHz clock. Therefore, streams

clocked out of this port only support a 44.1kHz sample rate. The CS98Ks PCM output ports share

a single clock rate which can be set by U1 to any desired frequency (AUD-DO_0, AUD-DO_1,

AUD_DO_2 and AUD_DO_3, sheet 8 of the schematics, are the data lines).


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17

Theory of Operation

The AV28 Signal Routing and Clocking Diagram, which follows, shows the fully-detailed audio

path, including clocking information. The legend at the bottom identifies which signals are analog,

which are digital, and what the relevant clock rates/sources are.

AV28 AUDIO PATH:

Signal Routing and Clocking

U1

S/PDIF

SOURCES

U304

74HC157

MUX

74HC157

MUX

U402

ZONE 1 OUT

ZONE 2 OUT

AUX EXT

OPTICAL EXT

TAPE EXT

VCR EXT

TV EXT

U501

0

1

2

3

4

5

6

OUT

CS8415

S/PDIF

MUX

AND

RCVR

OPTICAL

S/PDIF

RCVR

J501

ANALOG L/R

I2S: U303 PROVIDES CLOCK(ALWAYS 44.1 kSPS)

I2S: U1 OR U501 PROVIDES CLOCK (SOURCE DEPENDENT)

I2S: U303, U1 OR U501 PROVIDES CLOCK

S/PDIF: UP TO 96 kSPS

CS8405

S/PDIF

XMTR

U406

74HC157

MUX

U404ZONE 2

S/PDIF

DIGITAL

OUTPUT

J701

OPTICAL

S/PDIF

DRIVER

S/PDIF

RECORD

OUTPUT

OPTICAL

S/PDIF

RECORD

OUTPUT

VCR EXT

AUX EXT

TAPE EXT

TUNER

DVD MIXDOWN

TV EXT

U201

TEA6422

ANALOG

MUX1

2

3

4

5

6

1

2

3

ANALOG

L/R

SOURCES

CS4340

DAC

D/A

U503

D/A

CS4340

DAC

U202

U306

CS8405

S/PDIF

XMTR

U302

74HC157

MUX

U303

ZONE 2

ANALOG

L/R

VARIABLE

OUTPUT

ZONE 1

ANALOG

L/R

VARIABLE

OUTPUT

ANALOG

L/R

RECORD

OUTPUT

ZONE 1

S/PDIF

DIGITAL

OUTPUT

ANALOG

HEADPHONE

OUTPUT

NJM4556

BUFFER

U205

U1

CS98K

(LS500C)

DVD

DECODER

AC-97 PORT

(CONFIGURED AS I2S)

I2S

AUDIO

PORT

D0

D1

D2

D3

IN

ATAPI

XFACE

DVD ROM

74HC157

MUX

U502

74HC157

MUX

U505

CS4224

CODEC

A/D VOLUME

CELLD/A

U403

A/D D/AVOLUME

CELL

CS4224

CODEC

Port supports many sample

rates (but D0-D3 and IN

always share the same rate).

Port must always

run at 44.1kHz

sample rate

(clocked by U303).


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18

Theory of Operation

Although the AV28 is a 2-zone audio system, as discussed, the clocking limitations of the hard-

ware occasionally restrict which forms of audio can be simultaneously played out the two zones at

a given time. In these situations, Zone 1 (assumed to be the primary zone) would be allowed to

play the digital source while Zone 2 would be downgraded to playing an analog input source. For

example, a user could not play a DVD video disc in Zone 1 and simultaneously listen to the exter-

nal AUX digital input source in Zone 2, since the CS98Ks PCM output port can only clock out a

single digital stream at a time. The system, in this case, would use the CS98K to decode the DVDvideo discs audio for Zone 1, and would select the external AUX analoginputs to play in Zone 2.

The following tables describe the resulting audio formats when playing each combination of

sources simultaneously in the two zones:

As shown, for consistency, Zone 2 speaker outputs generally only plays the analog external inputs

(AUX, TAPE, VCR and TV). The exception here is when both Zone1 and Zone2 are listening to the

same external input; in this case, both zones will play the external digital inputs (if present), to

ensure that audio-path delays are identical for each zone.

When an external input source (AUX, TAPE, VCR or TV) is chosen for Zone1, the AV28 automati-

cally checks for the presence of a digital input stream and plays it if it exists. If it doesnt, the AV28

will default to playing the analog inputs.

TYPE OF AUDIO INPUT ALLOWED TO PLAY OUT EACH ZONE

(Zone 1 result shown on top in bold, Zone2 result shown on bottom in italic)

Source Selected for Zone 1

Off AM FM Tape AUX VCR TV DVD MP3CD CD

Off

OffOff

AnalogOff

AnalogOff

DigitalOff

DigitalOff

DigitalOff

DigitalOff

DigitalOff

DigitalOff

DigitalOff

AMOff

AnalogAnalogAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

FMOff

Analog

AnalogAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

Tape

OffAnalog

AnalogAnalog

AnalogAnalog

DigitalDigital

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

AUX

OffAnalog

AnalogAnalog

AnalogAnalog

DigitalAnalog

DigitalDigital

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

VCR

Off

Analog

Analog

Analog

Analog

Analog

Digital

Analog

Digital

Analog

Digital

Digital

Digital

Analog

Digital

Analog

Digital

Analog

Digital

Analog

TV

OffAnalog

AnalogAnalog

AnalogAnalog

DigitalAnalog

DigitalAnalog

DigitalAnalog

DigitalDigital

DigitalAnalog

DigitalAnalog

DigitalAnalog

DVD

OffDigital

AnalogDigital

AnalogDigital

AnalogDigital

AnalogDigital

AnalogDigital

DigitalAnalog

DigitalDigital

MP3CD

OffDigital

AnalogDigital

AnalogDigital

AnalogDigital

AnalogDigital

AnalogDigital

AnalogDigital

DigitalDigital

SourceSelected

forZone

2

CD

OffDigital

AnalogDigital

AnalogDigital

AnalogDigital

AnalogDigital

AnalogDigital

AnalogDigital

DigitalDigital

Key: Zone 1 performance hasbeen downgraded to

support Zone 2.

Zone 2 performance hasbeen downgraded to

support Zone 1.

Not allowed because the tuner cannot playAM and FM simultaneously, or becauseonly one disc can be in the tray at once.


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19

Theory of Operation

A hardware issue was found with the CS4224 codecs whereby audio passing through its A/D

converter emerges with left/right sample pairs mismatched; specifically, with left samples lagging

right samples by one sample clock. In other words, left/right sample pairs coming out of the ADC

together were not sampled together (right was sampled before left). The codecs DAC section has

the reverse problem: left samples will emerge ahead of the associated right samples. The net result

of this hardware bug is that audio passed fully through the codec (from ADC input to DAC output)

will have no improper left/right delays. However, audio passed only partially through the codec(only the ADC section, for example) will have left/right pairs emerge slightly out of phase. This

slight phase difference will have no noticeable effect when played through conventional stereo

speakers; however, slight spatial anomalies might be noticed if played through a surround-sound

system.

When playing-back an audio stream which was recorded using pre-emphasis (common in earlier

CDs, for example), the media centers analog Record Outputs will not properly apply de-emphasis,

as follows. The resulting audio will have more treble than desired:

Playing-Back Pre-Emphasized Audio Streams

Source Playing Zone 1

S/PDIF

NetworkOutput

(Used forCobalt II)

Zone 1

Variable

AnalogOutput

(Used forCobalt I)

Analog

Record

Output

S/PDIF

Record

Output

Headpho

ne

Output

Zone 2

S/PDIF

NetworkOutput

(Used forCobalt II)

Zone 2

Variable

AnalogOutput

(Used forCobalt I)

Internal CD-DA O.K. O.K. De-Emphasisis Missing

O.K. O.K. O.K. O.K.

External S/PDIF

Sources

O.K. O.K. De-Emphasisis Missing

O.K. O.K. O.K. O.K.

CS4224 Hardware Bug: Effect on Postman Console Audio Outputs

Source Playing Zone 1

S/PDIF

Network

Output

(Used for

Cobalt II)

Zone 1

Variable

Analog

Output

(Used for

Cobalt I)

Analog

Record

Output

S/PDIF

Record

Output

Headphone

Output

Zone 2

S/PDIF

Network

Output

(Used for

Cobalt II)

Zone 2

Variable

Analog

Output

(Used for

Cobalt I)Internal DVD Disc Left/Right

O.K.Left/Right

O.K.Right

Leads LeftLeft/Right

O.K.Left/Right

O.K.Left/Right

O.K.Left/Right

O.K.

Internal CD-DA Left/RightO.K.

Left/RightO.K.

RightLeads Left

Left/RightO.K.

Left/RightO.K.

Left/RightO.K.

Left/RightO.K.

Internal MP3 Disc Left/RightO.K.

Left/RightO.K.

RightLeads Left

Left/RightO.K.

Left/RightO.K.

Left/RightO.K.

Left/RightO.K.

Internal AM/FM RightLeads Left

Left/RightO.K.

RightLeads Left

RightLeads Left

Left/RightO.K.

RightLeads Left

Left/RightO.K.

External S/PDIF

Sources

Left/RightO.K.

Left/RightO.K.

RightLeads Left

Left/RightO.K.

Left/RightO.K.

Left/RightO.K.

Left/RightO.K.

External Analog

Sources

RightLeads Left

Left/RightO.K.

RightLeads Left

RightLeads Left

Left/RightO.K.

RightLeads Left

Left/RightO.K.


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20

Theory of Operation

5.0 Video Electronics

Video Block Diagram

Video signals may be generated internally (by U1) or passed-through from a set of external

(VIDEO INPUT) connectors. Internally generated signals include DVD playback and On Screen

Display (OSD) signals. OSD menus are accessed by pressing the SETTINGS button on the RF

remote. When not playing back a DVD or generating an OSD, the media center defaults to passing-

through external video signals, much as a VCR does. The media center is capable of being con-

nected to either NTSC or PAL televisions, where the desired format is selected via the OSD:

NTSC(National Television Standards Committee (USA) or National Television Systems

Committee). A television standard with 60 fields per second, 30 frames per second, and 525 lines

per frame. Variations of the standard include NTSC-M. A size used to digitize NTSC is 640x480

pixels. This standard is used in America and parts of Japan.

PAL (Phase Alternation Line). A television standard with 50 fields per second, 25 frames per

second, and 625 lines per frame. Variations of the standard include PAL-B/G. A size used to digi-

tize PAL is 768x576 pixels. This standard is used in parts of Africa, Australia, parts of Europe, and

in the U.K.

The video interface drives several kinds of video digital to analog converters to generate the

analog video monitor drive signals. U1 generates a standard ITU R.BT656 digital video data

stream with embedded synchronization. This standard uses an 8 bit bus, with interleaved Y, Cr, Cb

data. Synchronization information is embedded in the data stream, and exclusively uses values of

00 and FF (hex). Y values are from 1 to 254, with 1 being black. C values are from 1 to 254, with

128 being no chroma. The standard document should be consulted for further details on this bus.

The video encoder (essentially a video digital to analog converter), U601 on sheet 6 of the sche-

matic, is a 44 pin quad flat pack, containing extensive video processing circuitry. The data sheet

for this part (number CS4955) shows the block diagram and signal processing circuitry inside the

chip. The chip has many programmable registers inside, to set different operation modes, etc.

These registers are set by the main processor over a serial I2C bus (pins 32 and 33).

The CS4955 receives the ITU R.BT656 data bus, decodes the synchronization and separates the

Y, Cr, and Cb values into separate data streams. The three channels of video data are processed

appropriately, and sent to the digital to analog converters. Composite video is generated at pin 44,

S-video Y and C are generated at pins 48 and 47, and RGB or YCrCb are generated at pins 39,40,

and 43. The Composite video and S video are paralleled on the circuit board with the RGB (or

YCrCb) signals. The appropriate DACs are enabled by internal control circuitry, commanded by the

main processor, depending on the mode selected by the user. This allows either Composite and S-

video, or Component video, to be placed on the output jacks of the AV28 console.

Amp

NJM2267

U1

CS98000

CS4988

Video

Encoder

U601

NJM2284

Video

Switch

U602

Digital Analog

External

Video

U603, U604

Video

Output


21/73

21

Theory of Operation

The 3 video signals are sent to the internal/external video MUX, U602, a NJM2285 chip. This chip

will select either the internal or external set of video signals to be sent on further through the video

chain. The selection is made by the control pins 2, 7, and 12, driven by transistor Q601, a level

shifter driven by the main processor. No matter which mode the user selects, Composite and S-

Video, or Component video, the same circuitry is used in the video chain.

After internal/external selection, the three video signals are sent to the output video drivers, U603and U604. These are NJM2267 chips, with dual video channel capability. Each channel contains a

clamp circuit on the input, which does a DC restore on the video signal by clamping the negative

sync tip of the video signal to a DC voltage. The output driver drives the video signal through a

330uF capacitor (100-220uF on early units), and a 75-ohm resistor. This ensures equipment

compatibility even if there are DC differences between the AV28 and the driven equipment. The 75-

ohm resistor provides reverse cable termination for best signal integrity. Video sent through a

330uF capacitor would have low frequency drop-off, causing sag in the video signal. This is cor-

rected by the sag compensation pins of the NJM2267s, by sampling the video signal past the

capacitors, and correcting of any sag that occurs. This prevents synchronization problems with

video monitors that may otherwise occur.

For the Cr and Cb signal in component mode, and the C signal of the S-video signal, there is nosynchronization pulse for the input clamp of the 2267s to clamp to, which could distort the negative

tips of these chrominance signals. For these signals, the transistors Q601 and Q602 are turned on

by the port pins of U601, supplying enough DC voltage to the signal to raise them above the clamp

level, preventing any clamping action on them.

The CS4955 must receive a 27 MHz signal from the clock oscillator, with an accuracy of +- 1350-

hertz. This frequency is phase lock-looped inside the CS4955 to generate the 3.579545 MHz color

subcarrier for the composite video signal, and must be of high accuracy so that television monitors

can lock onto it and be able to decode color information to display.

6.0 Tuner Electronics

6.1 FM Tuner

The FM RF signal is provided by the F connector, J102, and goes to the FM front-end module. The

antenna supplied with the media center is the standard BoseFM dipole antenna. Contained within

the FM front-end is a tuned RF amplifier, FM local oscillator and mixer. The 10.7 MHz IF output

signal (pin 7 of the module) passes through a 10.7 MHz ceramic filter, CF101, to a FM IF amplifier,

and then back through a second ceramic filter, CF102. Transistor Q301 and related circuitry form

the FM IF amplifier that produces about 15 dB of voltage gain and provides the proper impedance

matching for ceramic filters CF101 and CF102. These FM IF filter stages reject unwanted FM

stations and noise.

The output signal from CF102 is fed to the LA1837 AM/FM detector IC, U101. This device contains

the FM IF limiter, FM detector, FM stereo MPX decoder, S-meter circuitry which is used for seek

processing, and most of the AM circuitry. The FM IF input signal to the LA1837 goes through

several gain/limiter stages and then to a single-tuned, coil-based discriminator circuit. The discrimi-

nator coil, T103, is adjusted for minimum second harmonic audio distortion. The recovered FM

composite signal appears on pin 23 of U101.


22/73

22

Theory of Operation

The composite audio signal is filtered by C124 and fed back into the LA1837 on pin 22. The value

of C124 affects FM stereo separation performance. Stereo MPX decoding is also performed by

U101 and the decoded left and right output signals are produced on pins 16 and 17. The pilot PLL

VCO is completely internal to the LA1837 detector IC, not requiring an external 456 kHz ceramic

resonator as in the older LA1836 and LA1851-based designs. The pilot PLL loop filter is formed by

C120, R118, and C122 on pin 14.

Capacitors C132 and C133 and the internal resistance of the LA1837 set the FM de-emphasis. For

a US unit the capacitor values are set to produce 75-uSec de-emphasis, and for Europe/Japan

they are set to produce 50-uSec de-emphasis. MPX filters, T104 and T105, reject the residual 19

kHz pilot tone and 38 kHz sub-channel demodulation components.

The FM and AM S-meter signals, which are at pin 11 and 12 of the LA1837 respectively, are

analog voltage levels that are propor tional to the FM IF/AM RF input signal levels. These signals

are used to control the FM stop level, FM force-mono level, and AM stop level. The nominal FM

stop/force-mono levels are:

Both S-meter signals are connected to a 2-input 6-bit analog to digital converter that resides in the

LC72144 PLL IC, U103. During factory final test booth tuner alignment the appropriate test signal

levels are injected into the UUT and the resultant ADC values for stop and force-mono levels are

stored in the Flash memory of the main board. Level scaling is applied to both the AM and FM S-

meter signals so that these signals do not saturate the dynamic range of the 3.3 V full scale A/D

converter.

6.2 AM Tuner

The signal from the external AM loop antenna enters through the 2.5 mm AM jack, J300, and is fed

to the AM front end module, T101. This module contains the varactor-tuned RF and Local Oscillator

(LO) tracking circuit. This part is pre-tuned by the manufacturer for proper alignment in this circuit

with AM antenna, and is further adjusted during factory alignment, if necessary. The RF tuned

output appears on pin 12 and is fed to the AM buffer FET transistor Q103. This buffered output is

sent to pin 27 of U101 which contains the AM RF amplifier, mixer, IF amplifier, AM detector, and

AM S-meter circuitry. The 450 kHz AM IF output signal that appears on pin 2 is filtered by the IF

filter, T102, and fed back into the IC on pin 4. The AM IF signal is demodulated by the LA1837 and

the audio output is sent to pins 16 and 17, which are the left and right outputs.

The AM seek stop processing and factory alignment is performed in a similar fashion to FM mode

processing. The S-meter voltage that corresponds to the desired AM stop level is stored duringfactory final booth tuner alignment in the main board Flash memory.

The nominal AM stop level is 56 dBuV/m at 1080 kHz.

Parameter Frequency Level

FM Seek Stop 98.1 MHz 30 dBf

FM Force Mono 98.1 MHz 40 dBf


23/73

23

Theory of Operation

6.3 Phase-locked Loop Tuning

The AM and FM local oscillators are controlled by the LC72144 PLL IC, U103. Control from the

main board selects the AM or FM band and the particular frequency. The 7.2 MHz crystal, Y102, is

connected across an inverting amplifier inside U103 to form an accurate and stable crystal oscilla-

tor. The 7.2 MHz oscillator is divided down to produce a 12.5 kHz reference frequency in FM mode

and 10 kHz reference frequency in AM mode. U103 divides down the AM or FM LO and comparesit to the appropriate reference frequency, generating an error signal on pin 21. This error signal is

integrated by Q208, Q207 and associated components, producing the tuning voltage at the collec-

tor of Q207. C150, C146, R146, and R217 control the gain and pole-zero locations of this active

lead-lag filter

The AM tuning voltage is further filtered by R108 and C106 and is fed to pin 14 of the AM front end,

T101. The tuning voltage varies the capacitance of the varactor diodes, which in turn tunes the AM

antenna and the AM LO. Similarly, in FM mode, the tuning voltage is filtered by R148 and C151 and

fed to the FM front end. As in the AM case, the tuning voltage is fed to varactors which tune the LO

frequency and RF filtering.

Both the PLL IC and the LC72722 PLL IC are controlled via a CCB bus interface. This is a bidirec-tional interface that sends control information, such as band select and frequency control, to the

PLL from the main board. This bus also sends status information, such as digitized S-meter value

and FM mono/stereo status, from the PLL to the main board controller

6.4 RDS Operation

This feature is only implemented in the European version of the AV28 media center.

The LC72722 Radio Data System (RDS) decoder IC, U102, is a single-chip system IC that imple-

ments the signal processing required by both the European RDS standard and US RDBS system.

RDS/RDBS systems can send digital information over the airwaves along with the standard FM

signal by adding a digitally modulated 57 kHz subcarrier to the normal FM composite signal. TheLC72722 includes a bandpass filter, demodulator, synchronization, and error correction circuits.

The input (pin 2) to the RDS IC comes from Q104, which buffers the FM composite signal at pin 23

of the LA1837. The timebase for the decoder is a crystal oscillator formed by the 4.332 MHz

crystal, Y101, the inverter internal to the IC across pins 12 and 13, and the two shunt capacitors,

C138 and C139. Control of the RDS IC is achieved by using the same CCB bus interface used for

the PLL IC.

6.5 Tuner Software

Software that controls the AM and FM tuner resides on the Main PCB.

The software that controls the FM tuner has provisions for an IF offset to optimize tuner perfor-mance for a given range of IF filters. The possible values of IF offset are -25kHz, 0, and +25kHz.

The software measures (counts) the IF frequency, and this offset is added to the count. In the

final console test, the value that minimizes THD at 98.1 MHz for an un-modulated 50dBF signal is

chosen and stored before other stop levels are set.

It should be noted that the stop levels for the tuner are also stored on the main board; the implica-

tion of this is that every time a different tuner board is mated with a main board, the stop levels

must be reset due to board-to-board component variations.


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Theory of Operation

7.0 Additional Electronics in the Console

7.1 Vacuum Fluorescent Display

A VFD module is installed in the front of the console. The module contains a microcontroller with

masked font tables, as well as built-in switching power supply/inverter and driver ICs for control-

ling the VFD glass. Communication to the VFD is serial through J103; see sheet 2 of SD254135.The protocol requires both clock (VFD_CLOCK) and data (VFD-DATA) lines, is single-direction

only, and runs at about 4800 baud. Q101 and Q106 are used to power-down the higher-current

sections of the VFD after the console has been off for about 10 seconds (reducing power con-

sumption and ensuring that the VFD is held in a reset state when the console is off).

7.2 DVD-ROM Drive

The DVD-ROM drive is a Toshiba SD-M1502 (soon to change to a SD-M1612). The drive is ca-

pable of playing DVD-video discs (including CSS decoding), CD-ROMs, and audio CDs. An ATAPI

cable for data and separate power cable connect the drive to the Main PCB (see sheet 2 of

SD254135). Q103 is used to reset the drives built-in microcontroller upon console power-up. The

drive remains active (in a paused state) for about 5 minutes after playing a CD/DVD to allow acustomer to return resume playback from the same location on the disc; after that, the drive is put

into a low-current standby mode via software command.

7.3 Console Keypad

A nine-button keypad is located next to the DVD-ROM drive tray. Six signals connect U1 to the

keypad: three signals represent the keypad rows, and three signals represent the keypad col-

umns. U1 identifies button presses by sequentially driving the KEYOUT lines (which activate

individual rows of keys) and reading-back the KEYIN lines (which have 75K pullup resistors inside

U1). If a button is pressed, the KEYIN line connected to that column of keys will be high (3.3V).

See SD256140.

7.4 Headphone Driver

The Headphone PCB holds the headphone jack itself, J200, and two inductors used to reduce

emissions and limit incoming ESD transients (L2001 and L2001). Pin 6 of the headphone jack is

used to sense when headphones are plugged in: when a customer inserts a headphone plug into

J200, pin 6 becomes shorted to ground. This pulls the HP-SENS line (normally pulled high by

resistor R242 on the Main PCB) to ground, alerting U1. U1 then mutes the appropriate audio

outputs. The headphone audio drive amplifier, U205, resides on the Main Board. This amp is config-

ured as a voltage follower (providing no signal gain).

Console Button Row Column

ON/OFF Top (driven by KEYOUT2, J102-3) Left (read by KEYIN2, J101-6)

SOURCE Top (driven by KEYOUT2, J102-3) Center (read by KEYIN1, J101-5)

VOLUME UP Top (driven by KEYOUT2, J102-3) Right (read by KEYIN0, J101-4)

ALL OFF Center (driven by KEYOUT1, J101-2) Left (read by KEYIN2, J101-6)

ENTER Center (driven by KEYOUT1, J101-2) Center (read by KEYIN1, J101-5)

VOLUME DOWN Center (driven by KEYOUT1, J101-2) Right (read by KEYIN0, J101-4)

OPEN/CLOSE Bottom (driven by KEYOUT0, J101-1) Left (read by KEYIN2, J101-6)

ERASE Bottom (driven by KEYOUT0, J101-1) Center (read by KEYIN1, J101-5)

STORE Bottom (driven by KEYOUT0, J101-1) Right (read by KEYIN0, J101-4)


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Theory of Operation

7.5 TV Power Detector

The infrared power command for televisions toggles the power state of the television; in order to

automatically turn a customers television on when a video source is selected, the power state of

the TV must be known to determine if sending a power toggle command is necessary. The circuit

detects the presence of the televisions horizontal sweep frequency; standard NTSC and PAL

monitors use 15750 Hz, and line-doubled, HDTV, or 480p monitors use 31500 Hz.

An external dongle plugs into the tuner board at J105; the dongle contains 25 turns of wire inside a

plastic enclosure. When placed properly (at the back of the unit near the deflection coils) on the

television, the dongle will output 20~200 mV of signal.

The TV power detector circuit is on the tuner board. See sheet 3 of SD256131.

The power detection circuit is built around U303, an NJM3403 quad op-amp IC. C328 and L302

form a highly peaked low-pass filter about 15750 Hz; C324, C325, and L303 form a similar filter

about 31500 Hz. The filters boost the voltage of their passbands about 10 times. The outputs of

these filters are fed to active band-pass filters constructed of sections of U303; the active filters

have a Q of 5 (allowing for component variation) and a gain of 20. The outputs of these activeband-pass filters (if present) are rectified and summed by D302. D303 performs a voltage shift

equal to that of the rectifier so that a reference voltage for the comparator can be generated with

diode drop compensation.

The remainder of U303 serves as a comparator and a Schmidt trigger. The comparator compares

the rectified signal with 0.5V; if either sweep frequency present, the comparator output will go high.

The Schmidt trigger section, designed to minimize chatter at the circuit output, drives the TV_ON

signal to U1 to indicate the detected power state of a television.


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8.0 LS28/35 Bass Module Issues

The LS28/35 bass module is sold as a system with the AV28 media center and is mentioned for

reference. Refer to the Lifestyle28 and 35 Digital AcoustimassPowered Speakers service

manual part number 264562.

8.1 LEDs

The amber and green LEDs on the DSP board serve to provide information about the status and

operation of the speakers DSP board. The following is a summary of the various possible states of

the LEDs and a functional description of the state(s) represented.

Green LED: The green LED serves a dual purpose: general system health and serial data

received. The green LED will blink once per second with a 50% duty cycle (i.e. on for second,

off for second) if the system booted and is running normally. If the unit is in the SmartSpeaker

Off condition, the green LED will blink briefly (approx. 0.1s ON time) once every 5 seconds.

The green LED will also toggle whenever a serial data byte is received. This will interrupt the

normal 1-second blink rate. The green LED blinking faster than 1 Hz usually indicates that it is

receiving serial communications.

Amber LED: The amber LED serves to signal 3 conditions: power applied/boot status, S/

PDIF status and clipping status. When power is first applied the amber LED will light briefly. If the

PROM FLASH checksum is incorrect or hardware does not pass power-on self test, the green

LED and amber LED will alternately blink at approx. a 5 Hz rate. If the green LED is blinking at its

normal, 1 Hz rate, a blinking, 1Hz amber light indicates that there is no valid S/PDIF signal present:

If the amber LED is off while the green LED is blinking normally, then valid S/PDIF is present and

being received. Finally, the amber LED will briefly blink (in this case, only when valid S/PDIF is

present) when the satellite amps are clipping. This should only occur when playing the system at

extremely high levels.

8.2 DIP Switches

The LS28/35 bass module has a set of four DIP switches, accessible from the back connector

area. Three of these switches (switches 1, 2 and 3) set the Room Code of the speaker, and must

match the three Room Code DIP switches on the remote control (switches 7, 8 and 9) used with

that speaker. Switch 4 on the speaker is only used in manufacturing/test to enter TAP mode, and

should nominally be left DOWN.

9.0 Legacy Speaker Issues

9.1 Protocol Setup

The AV28 media center supports legacy (existing) Bosepowered speaker systems in both Zone

1 and Zone 2. However, these systems (AM25P/30P II digital bass module and LSA) require the

console to send control commands using the older CD-5 Serial Data Port Protocol, which is NOT

the default smart speaker protocol used by AV28 media center. To enable this older protocol, the

user must use the OSD (Settings/Setup) menus to change either the Zone 1 Speaker Protocol or

Zone 2 Speaker Protocol from Normal to Legacy mode.

Theory of Operation


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9.2 Addressing

The older CD-5 smart speaker protocol allowed addressing up to four speakers (rooms) per

zone, referred-to as Speakers A, B, C and D. Similarly, older Bose Lifestyleremote controls had

four DIP switches used for selecting which of these speakers should be controlled. All AM25P/30P

II digital bass module powered speakers are hard-wired as smart speaker address A. All LSAs

are hard-wired as address B.

The AV28 media center's RF remote has three Room Code DIP switches (not implemented at

printing of this manual), allowing up to seven speakers per zone to be addressed, referred-to as

Rooms A through G. Since this addressing scheme is different than that used by older systems, a

translation table is required to understand how to use AV28 media centers RF remote when

controlling AM25P/30PIIdigital bass module or LSA (when a zone is set for legacy mode), as

follows:

The table shows that up to three AM25P/30P IIdigital bass modules and three LSAs (labelled #1,

#2 and #3 here) can be addressed by a AV28 media center remote control. Note that a special

adapter box would be required to actually hang more than one AM25P/30P IIdigital bass module

and one LSA off each zone of the AV28 media center . *To control a single AM25P/30P IIdigital

bass module, it is recommended that the user set switches 7, 8 & 9 on the users AV28 RF remote

to 010 (Room C, where 0=down and 1=up). To control a single LSA, it is recommended that a user

set these switches to 110 (Room G).

Theory of Operation

Postman RF Remote Room Switches for Legacy Mode

Postman Remote's Room

DIP Switch Pattern(switches 7,8&9)

Resulting CD5 Smart

Speaker Message'sHeader

Legacy Speaker that the Console

Allows This Remote to Control

000 (Room A) 0x31 Cobalt I #1

001 (Room B) 0x35 Cobalt I #2

*010 (Room C) 0x39 Cobalt I #3

011 (Room D) 0x3D All Rooms

100 (Room E) 0x32 LSA #1

101 (Room F) 0x36 LSA #2

*110 (Room G) 0x3A LSA #3

111 (All Rooms) 0x3E All Rooms


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10.0 Software

10.1 FLASH Update Capability

The software in the AV28 media center is stored in FLASH. During boot, the software is decom-

pressed from the FLASH to the DRAM, where it is executed. U1 can update the contents of the

FLASH, so the software is field upgrade-able. Additionally, the console can update the FLASHwhere the DSP stores its code in the LS28/35 bass module using the speaker cable.

10.2 FLASH Update Procedure

Note:A software update disc can be obtained by calling Bose service. If you have a software

update disc, check the service intranet site or call Bose service to make sure you have the latest

version.

10.3 Software Version

To find out which version of software is loaded in a console, first press the [ALL OFF] button on the

keypad. Next, press and hold the [STORE] key and press the [ENTER] key one time. The soft-ware version is displayed on the VFD in the following format: SV C:(dateCode):(version)-(build)

for example, SV C:092501:1.0-0125 would indicate Version 1.0 code made from build #125 on

September 25, 2001.

10.4 User Settings Stored in FLASH

Certain user settings (tuner presets, OSD settings like preference for Film-EQ in a particular

source) and tuner calibration coefficients are stored in a protected area of FLASH. These are not

overwritten when the software is updated. There are two important consequences:

Sending an FU [Flash Update] command via ETAP will erase the user settings (but not thetuner calibration).

After setting any preferences (house code, tuner presets, OSD settings), you must cycle the

power on and off with the remote and wait a few seconds before unplugging the unit. When the unit

is powered off by the remote, the user preferences set in that session are stored in FLASH.

Theory of Operation


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Disassembly/Assembly(Refer to Figure 3)

1. Top Cover Removal

1.1Remove the six screws (28) that secure

the top cover (7) to the base (9).

1.2Release the catch at the right rear corner

of the top cover. Lift off the top cover.

2. Top Cover Replacement

2.1Align the top cover (7) with the base (9)

and press down at the right rear corner to

secure the catch.

2.2Replace the six screws (28) that secure

the top cover to the base.

3. DVD/CD Assembly Removal

3.1Perform procedure 1.

3.2Pressing outward on the four tabs located

on the base (9) at the bottom corners of the

DVD/CD bracket (15), lift out the DVD/CD

assembly (1).

3.3Remove the two connectors from the

DVD/CD assembly.

3.4Remove the four screws (22) that securethe DVD bracket (15) to the DVD assembly.

4. DVD/CD Assembly Replacement

4.1Align the DVD bracket (15) with the DVD

assembly (1). Replace the four screws (22)

that secure the DVD bracket to the DVD

assembly. Refer to figure 3 for DVD bracket

orientation.

4.2Connect the two connectors to the DVD/

CD assembly.Note: Make sure the ribbon cable connector

key is on the top when inserting the connec-

tor. Line up the connector to the pins on the

receptacle and gently push in. Do not force

the connector or push on the connector at an

angle. Damage to the pins may occur.

4.3With the DVD/CD assembly (1) label side

up, align the tabs on the DVD/CD bracket

(15) with the four tabs located in the base (9).

Press downward on the corners of the DVD/

CD assembly until all four tabs snap into place.

5. Tuner PCB Removal


5.2Grasp the front edge of the tuner PCB (3)

and lift up until it is at a 450angle.

5.3Grasp the tuner PCB bracket support

(21), which is located under the tuner PCB,

and pull it to the left slightly to clear the

headphone jack PCB. Then pull up and

forward on the tuner PCB bracket support to

release the tuner PCB.

5.4Remove the ribbon cable from connector

J103.

6. Tuner PCB Replacement

6.1Attach the ribbon connector to J103.

6.2Align the posts on the tuner PCB support

bracket (21) with the three locator holes in

the base (9).

6.3Holding the tuner PCB (3) at a 450 angle,

align the two tabs located at the rear of the

tuner PCB with the two cutouts located at the

rear of the base.

6.4Lower the front of the tuner PCB until it

rests on the tuner PCB support bracket.


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Disassembly/Assembly(Refer to Figure 3)

7. Main PCB Removal


7.2Disconnect the cables from J102, J103,

J106, J213, and the DVD/CD mechanisms

ribbon cable.

7.2Release the main PCB (2) from the four

locking tabs located on the base (9). Two

located at the front and one located on each

side of the PCB.

7.3Lift up the front of the main PCB and slide

it forward and up.

8. Main PCB Replacement

8.1Lower the rear of the main PCB (2) into

the base (9) so the connectors protrude out

the rear of the base.

8.2Align the headphone jack PCB (2) with

the hole in the side of the base. The main

PCB (2) and tuner PCB support bracket (21)

will secure the headphone jack PCB in place.

8.3While applying rearward pressure on the

PCB, press downward at the locations of the

four locking tabs; two located at the front andone located on each side of the PCB.

8.4 Connect the cables to J102, J103, J106,

J213, and the DVD/CD mechanisms ribbon

cable.

9. VFD Module Removal


9.2 Release the VFD module (6) from the twolocking tabs, which are located at the two top

corners of the VFD module. Pull up the VFD

module.

9.3Disconnect the cable from J103, located

on the main PCB (2).

10. VFD Module Replacement

10.1 Connect the cable to J103, located on

the main PCB (2).

10.2Slide the VFD module (6) into the VFD

holder on the base until the two locking tabs

snap into place.

11. IR PCB Removal


11.2Lift up the bezel (41).

11.3Release the IR PCB (2) from the locking

tab located on the left side of the IR PCB. Lift

up on the IR PCB and then slide it to the left.

11.4Disconnect the cable from J1000.

12. IR PCB Replacement

12.1 Connect the cable to J1000.

12.2Slide the IR PCB (2) under the catch on

the right side.

12.3While aligning the IR PCB with the two

locator guides, press down until the IR PCBsnaps into place.

13. Laser Current Measurement Access


13.2Remove the four screws that secure the

bottom cover of the DVD/CD assembly (1) to

its chassis. Lift off the bottom cover.

13.3Refer to figure 6 for the location of thelaser current measurement points and the

laser current information located on the

mechanism labels.


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1.Open a terminal window. Click: Start/Pro-

gram/Accessories/Hyperterminal/Hyperterminal

2.In the Connection Description window, type

the name AV 28 media center then click OK;

any name may be entered.

3.In the Connect To window, select the COM

port on your computer that you will be connect-

ing the AV28 media center to and then click OK.

4.In the COM1 Properties window, make the

selections in the various fields as shown.

5. In the Hyperterminal window, click on File/Properties. In the Properties window, click on

the Settings tab, make the selections in the

various fields as shown.

Setting-up a Computer to Issue TAP Commands

6.In the Settings window, click on

ACSII setup and make the selec-

tions and changes as shown.

Note:Terminal programs other than

hyperterminal can be used.


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General Test Procedure Notes

1. The media center will not turn on unless it senses a speaker connected to the Zone 1 (or Zone

2) speaker connector. Connecting a speaker cable to the Zone 1 (or Zone 2) speaker connector or

physically shorting J301 pin 8 and 5 together will allow the media center to turn on. Disconnecting

a Zone output will cause that Zone to turn off.

2.After completing any or all adjustment procedures requiring TAP commands, the FLASH

memory must be updated to store the adjustments. Refer to the Adjustment/Performance Verifica-

tion Procedure 10.

3.All AM and FM adjustments must be performed when replacing a main or tuner PCB in order to

ensure an optimized tuner. All TAP related tuner adjustments are stored in FLASH memory on the

main PCB.

4. Functional/Performance Verification Tests: Contain tests to verify the performance and function

of the AV28 media center.

Adjustment/Performance Verification Procedures: Contain procedures to optimize the performance

of the AV28 media center.

1. TAP Test Cable Connection

1.1 Connect the test cables, part number

264565, DB-9 connector to the RS-232 COM

port on your computer. Connect the test

cables 3.5mm plug to the serial data jack on

the AV28 media center.

1.2 With a Hyperterminal window open, apply

power to the AV28 media center. A response

similar to the following will be displayed on

your computer screen.

Reset!

Fixture Detection ... Failed.

Phase 1 Input Pattern :11010111101

Zone Sense Bus ... Failed.

Memory Tests ... Passed.

Ready for test...

>Self-test phase has expired...

UEI Chip Result : BOS0

IR Loopback ... Passed.

Tuner Board Variant : USA

RF House Code : 0010

Booting Cirrus API...

Initializing Encoder...

ive Info...

CD/DVD Drive ... Passed.

Booting Application...

Issuing TAP Commands to the AV28 media center

2. Verify the media center communicates in

TAP mode

2.1Type the command PS C and hit Enter.

A response similar to the following will be

displayed on your computer screen. (power

on self test results).

Fixture Detection ... Failed.

...Phase 1 Inputs : Not Found.

I2C Bus ... Passed.

TAP Bus ... Failed.

38758437 bose av28 service manual

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