Philips DVDR-75 Service manual

Philips DVDR75

Technical Training Manual

Philips Service and Quality/Training One Philips Drive Knoxville, TN 37914-1810 P. O. Box 14810 PH: 865-521-4397 FAX: 865-521-4818 EMAIL: TECHNICAL.TRAINING@PHILIPS.COM

Introduction

This manual is intended for use by the Service Technician. There are two versions of the DVDR75. The first four digits of the Product Number indicates the version. The Product Number is similar to a Serial Number. It will read VN02 or VN04. The VN04 is the newer of the two. The VN04 uses an updated Digital Board that contains the functionality of the DVIO Board. When there are two versions of a circuit, the title to the section will have one or the other in the title, VN02 or VN04.

The first portion of this manual contains a basic description of disc based data playback and recording technologies. Self Diagnostics are included to aid in troubleshooting. Technical Descriptions of the circuitry are followed by a Troubleshooting Section.

The DVDR75 is the forth generation in a line of DVD recorders. Recordings can be made from broadcast transmissions, and from other analog or digital sources. The DVDRW format allows the user to record and erase a disc many times. The recorded discs will play on most existing and future DVD players. The DVDR75 has a connection for DV or Digital camcorders via an I-Link or Firewire connection. This connection technically is called an IEEE 1394 connection. This machine records on 4.7Gbyte DVD+R and DVD+RW discs. This machine uses a real-time MPEG2 Variable Bit Rate, VBR, Video encoder. The DVDR75 plays back DVD Video, Video CD, Audio CD, CD-R, and CD-RW discs.

Its many features include: Favorite Scene Selection for easy editing, Index Picture Screen for instant overview of contents, Digital Time Base Corrector, Digital Audio output (DTS, AC3, MPEG, PCM), TruSurround for 3D sound, Zoom + Perfect Still. It is Widescreen, 16:9 compatible, and has a Universal Remote Control, 20 disc resume, Disc Lock, and One Touch Recording.

Virgin Mode

The DVDR75, when first hooked up, needs to get information from the user about what language and what local broadcast system the unit is going to operate with. Use the remote to make those selections. The unit will not operate until this process is completed. If you want the recorder to start up in Virgin mode, unplug the recorder. Plug the recorder in again while holding the STANDBY-ON button.

DVD Basics

Philips with nine other manufacturers chose a format specification for DVDR and RW on March 16, 2001. This format uses Real Time recording. Its recording is compatible with DVD-Video, and DVD ROM. The data blocks use lossless linking. The physical layout matches very closely to that of a DVD ROM. See Figure 1. It also uses Direct Overwrite when a RW disc is used.

Figure 1 – DVD ROM Disc

Laser Technology

The DVD and CD share much of their technology. We will start with CDs and work our way to the DVD. CDs use a red laser created by a diode and lens system often called a Light Pen. Refer to Figure 2. The narrow beam of light is focused onto the reflective layer of a disc. At the instant that focus is achieved, the disc is spun. The laser starts on the innermost tracks of the CD and reads outward. At the beginning of the disc is the Table of Contents. At the bottom of the Light Pen are Monitoring Diodes. The Monitoring Diodes provide information about focus and tracking. Data is retrieved from the disc in the form of pulses of light reflecting from the disc. The pulses are created by Pits in the Reflective Layer of the disc. The Pits reflect less light than the intact surface of the Reflective Layer, called Lands. The data is binary. A 1 is generated when the light transitions from bright to dim and dim to bright. The time between is a series of zeros determined by the data rate.

Disc Mechanical Layout

The CD is a plastic disc 120mm in diameter, with a thickness of 1.2mm. Refer to Figure 3. It has a silver colored Reflective Layer. The maximum playing time for a music recording on a Compact Disc, CD, is 74 Min.

Figure 2 – CD Laser Operation

Figure 3 - CD Disc

The CD is less vulnerable to damage than an analog record. That does not mean it does not have to be treated with care. Dirt and heavy scratches can interfere with playability.

As shown in Figure 4, the CD is subdivided into three parts: the Lead In Track, the Program Area, and the Lead Out Area. These three sections together are considered the Information Area. There is a hole in the center for holding the disc. The disc is held between two equally sized concentric rings. The rings have an inner diameter of 29mm and an outer diameter of 31mm.

The Data on the disc is recorded on a spiral shaped track with pits and lands. The reflective side of the disc contains the tracks.

The production of a disc is a high tech process explained in Figure 5. The process starts with glass that is photo etched. The glass is silver plated and is used as a form for a metal cast. The metal cast is used to stamp a nickel Mother Stencil. The Mother Stencil is used to stamp the Son Stencil. Son Stencils are used to stamp the foil of the discs. A protective layer and label are added.

Figure 4 - The Disc

Figure 5 - Creating a CD

Read Process The Servo circuit is responsible for focusing the laser and moving the Light Pen to follow the spiraling tracks on the rotating disc. The digital High Frequency information, HF, is demodulated and stored in RAM. When the RAM is half full, the data is fed out to the Digital to Analog Converters.

The speed of the rotating disc is servo controlled to keep the RAM half full. The analog signals are amplified and sent to the output connectors.

Record Once Technology

Disc Mechanical Layout From an external point of view, a DVD is the same as the CD. Recordable media creates the need for three physical layouts. There are three possible states of a disc: a blank disc, a partially recorded disc, and a full or finalized disc. The difference is in the way the Information Area is divided. The Information Area of a blank disc extends from 22.35 mm centered on the disc to 59 mm centered on the disc. Refer to Figure 6. A partially recorded disc’s Information Area has

four sections: a PCA/RMA area, a Lead In Area, a Recorded Program Area, and a Recordable Program Area. See Figure 6 for the dimensions. The PCA Area is the Power Calibration Area, PCA. The RMA Area is the Recording Management Area. A fully recorded or finalized disc’s Information Area has three sections: A

lead in Area, the Program Area, and the Lead Out Area. See Figure 7 for the dimensions.

The disc’s recordable layer contains major differences from that of a stamped disc. The blank disc has a Pre-groove stamped into the recordable layer of the disc. This is polycarbonant for DVD+Rs and organic dye material for DVD+RWs. This spiral Pre-groove is for the Servo circuit to provide a mechanical reference during recording. The dye based RW recordable layer provides a reflectivity of 40% light return and 70% light return. 40 percent reflectivity represents Pits and the 70% represent the Lands.

Record Process The record process shares most of its mechani-

Figure 6 – A Partially Recorded Disc.

Figure 7 – Fully Recorded or Finalized Disc

cal operation with that of the play process. The main difference is how the Servo is locked to the disc. The Servo follows the Pre-groove for Radial Tracking and disc speed. The speed of the disc is locked to a wobble signal that is part of the spiral grove stamped into the disc.

The intensity of the laser beam is modulated from playback intensity to write intensity. As the disc reads the Pre-groove, the laser arrives at a position where a Pit is to be formed. The laser power increases from 4mW to 11mW. This raises the temperature of the disc to 250 degrees Celsius. The recordable layer melts, reducing its volume. The polycarbonate flows into the space vacated by the dye. The modulation from read laser power to write laser power forms a pit and land pattern effectively the same as a prerecorded disc.

Re-recordable Technology

Disc Mechanical Layout Disc usage mechanically is identical to the recordable media. The only difference is the chemical make up of the recordable layer. The recordable layer is made up of an alloy of silver, indium, antimony and tellurium.

Re-Recording Process

The Re-Record process shares much of its operation with that of a CDR. The blank disc’s

Information Area is in a polycrystalline state. During recording, the laser power is modulated from 8mW to 14mW. 8mW is the playback laser power and 14mW is the record laser power. The polycrystalline state of the recordable surface changes, or melts at 500-700 degrees C into an amorphous state. The melted, amorphous areas reflect light less than the crystalline areas, creating a pattern similar to the stamped CD. A major difference of CDRWs from CDRs is the ability to erase.

The Erase Process To Erase a CDRW disc, the recordable layer must be returned to its polycrystalline state. This is done by heating up the temperature of the recorded surface to 200 degrees C. This is less than the melting point. This is done at X2 recording speed. The slower speed allows time for the alloy to return to its proper state. This takes approximately 37 min. Some software erases the just the TOC on the disc and allows the disc to be rewritten. This method is not as reliable

Over Writing Process Over writing combines the processes of erasing and writing. When the disc and Light Pen are in position to start writing the new data, the laser power starts modulating in the same manner as it does for normal recording with one difference. During the time there is to be a land, the laser power goes to the erase level rather than the playback level.

Figure 8 – Mechanical Layout of a DVD

DVDs All of the previously discussed technologies apply to the DVD. Like CDs, DVDs are also stamped into play only discs. In this discussion, we will point out the differences between DVDs and CDs. If you are new to disc based technology, you will want to start with the information preceding this discussion.

DVD Disc Mechanical Differences

Most DVDs are single sided, however, the DVD specification allows for two readable layers, and the disc can be double sided. We will start our discussion with single sided, single layered discs. A Digital Versatile Disc, DVD, looks very similar to a CD. Refer to Figure 8. The Clamping Area is larger, starting at 11 mm centered to 16.5

mm centered. The Lead In Area is smaller, measuring 22.7 mm centered to 24 mm centered. The Information Area is limited to 116mm centered.

Two of the big differences between DVDs and CDs are the Pit and Land sizes, and the track widths. Refer to Figure 9.

The Manufacturing process of a DVD is comparable to that of a CD. The main difference is the thickness. The DVD can be a double sided product. Each side is .6mm. The two sides are glued back to back, producing 1.2mm total thickness.

Figure 8 - DVD Mechanical Layout

Figure 9 – DVD and CD Pit Structure.

DVD

Wobble

A Pre-groove is stamped on writable discs. All recordable DVD media types feature a microscopic wobble groove embedded in the plastic substrate. This wobble provides the recorder with the timing information needed to place the data accurately on the disc. During recording, the drive's laser follows this groove, to ensure consistent spacing of data in a spiral track. The walls of the groove are modulated in a consistent sinusoidal pattern so that a drive can read and compare it to an oscillator for precise rotation of the disc. This modulated pattern is called a wobble groove because the walls of the groove appear to wobble from side to side. This signal is only used during recording, and therefore has no effect on the playback process. Among the DVD family of formats, only recordable media use wobble grooves.

Dual Layer Discs Two information layers are separated by a thin transparent layer. Refer to Figure 11. The first layer is partially transparent. This allows the second layer to be read through the first layer. Both layers are read by controlling the focus. There are two methods for reading the data of a Dual Layer disc, PTP and OTP. Refer to Figure 12.

PTP is Parallel Track Path. That means the Lead In and Out Areas of the two layers correspond to each other. Each Lead In Area is on the inner portion of the disc, and the Lead Out Area is on the outer portion of the disc. This is useful to link data between the layers.

This allows instant access to the additional data or scene. OTP is Opposite Track Path. This method links the end of one layer to the beginning of the other. The Lead In Area is still on the

Figure 11 – Dual Layer DVD

Figure 10 - Wobble Pregroove

inner portion of the disc. There is a Middle Track Area on both of the layers located on the outer portion of the layers. The Middle Track Area links the data on the two layers together. The Lead Out Area is on the second layer on the inner portion of the disc.

Capacity Because a stamped DVD can be Dual Layered and Double Sided, there are four different capacities. Refer to Figure 13. These capacities strict-

ly pertain to raw data. The time available for Video and Audio has many extra factors that determine the length of time on each side or layer. The picture complexity and the amount of movement in the picture affect compression and time on a disc. The number of languages affect the time on a disc. The type and quality of the Audio has an affect on the time also. It can be mono, stereo, or AC-3. Therefore, the media itself determines the capacity in time on the disc.

Figure 13 – DVD Multi-Layered Capacities

Figure 12 – PTP and OTP Layout

Description

The VN02 products have this feature. The End User/Dealer Self Diagnostics work without the need for other equipment. A number of hardware tests are automatically executed to check for faults in the recorder. The final test, number one, routes video to the Composite Out jack. The signal is a Pal Color bar signal. Most televisions will show the bars in B+W. This is dependent on the pull in range of the monitor, as the frequencies are shifted as compared to NTSC. The diagnosis ends with a “FAIL” or “PASS” message.

If the message “FAIL” appears on the display, an Error Code is displayed. If the message “PASS” appears, the tests have been executed successfully. There can still be a failure in the recorder.

The tests do not cover the complete unit. The following list describes the tests being performed while the test number is being displayed on the Front Panel.

To place the unit in the Self Test Mode, hold the Play pushbutton on the Front Panel while suppling AC power to the unit. The word BUSY appears on the display followed by test number. The display counts down numerically to test if it is performing.

The following is a list of the tests.

“Test Number” is displayed on the Front Panel “Name” of the test Description of the test

22 SdramWrR Checks all memory locations of the 4Mbyte SDRAM

21 HostdDramWrR Checks all the DRAM connected to the microcomputer on the Digital Board

20 HostdI2cNvram

Checks the data line (SDA) and the clock line (SCL) of the I2C bus between the host decoder and NVRAM

19 SAA7118I2c Checks the interface between the Host I2C controller and the SAA7118 Video Input Processor

18 VideoEncI2c Checks the interface between the host I2C controller and Empress

17 AudioEncI2c Checks the I2C connection between the host decoder and Empress

16 AudioEncAccess Tests the HIO8 interface lines between the host decoder and the audio encoder

15 AudioEncSramAccess Checks the access of the SRAM by the audio encoder (address and data lines).

14 AudioEncSramWrR Tests the SRAM connected to the audio encoder

13 AudioEncInterrupt Tests the interrupt line between the host decoder and the audio encoder

12 VsmAccess Checks whether the VSM interrupt controllers and DRAM are accessible

11 VsmInterrupt Checks both interrupt lines between the VSM and the host decoder

User Self Diagnostics (VN02)

10 VsmSdramWrR Tests the entire SDRAM of the VSM

9 Clock11.289MHz Switches the A_CLK of the micro clock to

11.2896 MHz

8 Clock12.288MHz Switches the A_CLK of the micro clock to 12.288 MHz

7 BeS2Bengine Checks the S2B interface with the Basic Engine by sending an echo command

6 DisplayEcho Checks the interface between the host processor and the slave processor on the display board

5 AnalogEcho Checks the interface between the host processor and the microprocessor on the Analog Board

4 AnalogNvram Checks the NVRAM on the Analog Board

3 Tuner Checks whether the Tuner on the Analog Board is accessible

2 LoopAudioUserDealer Tests the components in the audio signal path: The host decoder on the Analog Board, the audio encoder, the VSM. The Audio is internally looped back thru the Digital Board

1 LoopVideoUserDealer Tests the components on the Video signal system path: - The VIP- The Video encoder- The VSM- The host decoder. The Analog Board On Video signal is internally routed back to the Digital Board.

The User Self diagnostics in the VN04 product are very different than the VN02 product. It has a different Digital Board.

Press Play and apply AC power. The display will flash quickly through a more technical display of the Nucleus (test) it is performing. If an error is found, the Nucleus Code and an Error Code will be displayed. Use the Service Manual to look up the code.

User Self Diagnostics (VN04)

Description

The VN02 products have this feature. The Manual Diagnostics provide the opportunity to perform tests and exercise the unit in a way that helps determine which of the DVD recorder’s circuit boards are faulty. If no Errors are found, it performs an endurance loop test.

To successfully perform the tests, the DVD recorder must be connected to a monitor via the video out. The Servicer must respond to what is seen and heard on the monitor. (i.e. to approve a test picture or a test sound). Some tests require that a DVD+RW disc be inserted.

Structure of the Player Script The player script (Manual Diagnostics) tests the circuit boards in the DVD recorder: the Display PCB, the Digital PCB, the Analog In/Out PCB and the Basic Engine.

The Player tests are done in two phases, interactive tests and a burn in test. The interactive tests depend strongly on user interaction and input to determine the results and to progress through the full test. The Burn-in Loop test will perform the same set of tests as the dealer test, but it will loop through the list indefinitely. Is is especially useful if you reset the Error Log. You can do this using ComPair. You can then read the error codes using ComPair.

Step by Step Description

1 Press OPEN/CLOSE and PLAY buttons at the same time and provide AC to the recorder to start the player script. Press Play to perform the test described on the display. Press Stop to skip the test and go to the next test. Press Record to indicate to the Microcomputer the desired result malfunctioned.

2 The display shows FP SEGM. Press PLAY to start the test. First the starburst pattern is lit. Press Play each time to advance. Then the horizontal segments are lit, followed by the vertical segments and the last test lights all the segments. After each of the four tests, the user has to confirm that the correct pattern was lit. Pressing PLAY confirms the correct pattern was lit. Pressing RECORD indicates that the correct pattern was not successfully lit. Press STOP to skip this or any test.

3 The display shows FPLABELS. Press PLAY to advance. All labels should be lit.

4 The display shows FPLIGHT ALL. Press PLAY to advance. Everything should be lit.

5 The display shows FP LED. Press PLAY to advance. The red Record light comes on. Press PLAY to confirm it lit. Press STOP to skip this test.

6 The display shows FP KEYBRD. All keys have to be pressed to get a positive result! This includes the Power button. Press PLAY for more than two seconds to confirm that all the keys were pressed and that it was shown on the display. Press STOP for more than one second to skip this test.

7 The display shows FP REMCTL. Press PLAY to confirm that a key on the remote control was pressed and shown on the local display. Only one key has to be pressed to get a successful result.

Manual Diagnostics VN02

8 The display shows FPDIMMER. Press PLAY to activate the dimming feature. Press Play to confirm that the text on the local display was dimmed.

9 The display shows ROUTE VID. Press PLAY to advance.

10 The display shows ROUTE AUD. Press PLAY to advance.

11 The display shows COLORBAR ON.Press PLAY to advance. An NTSC Colorbar Pattern should appear at the output. Press PLAY to advance.

12 The display shows PINKNOISE ON. The monitor should produce Pink noise.

13 The display shows PINKNOISE OFF. Press PLAY to advance.

14 The display shows BE RESET. Press PLAY to Reset the Basic Engine (Mechanism/Servo PCB).

15 The display shows BE TRAY OPEN. Press PLAY to open the tray. Place a RW disc in the tray.

16 The display shows BE TRAY CLOS. Press PLAY to close the tray.

17 The display shows BE WRITE READ. This requires a RW disc to be in the machine. The BE resets and a small write is preformed, and then a read. This will take 20 seconds or so.

18 The display shows BE TRAY OPEN. This opens the tray.

19 The display shows BE TRAY CLOS. This closes the tray.

20 The display shows ERRORLOG READ. If there was an error, a code will be displayed. If you press PLAY, the diagnostic script will start an endless loop. If the unit fails a test, the local display will display FAIL and the error code.

In case of a failure, the display shows “ FAIL XXXXXX “The description of the shown error code should be found in the list in the Service Manual. Once an error occurs, press the STOP key to jump over the failure and to continue the diagnostics.

There is a Error Code Table in Force Manual

2064.

VN04 product does not have Manual Diagnostics.

If you try to place the unit in diagnostic mode in the same manner as the VN02 product, there is no display and the unit is locked.

Overall Block

Key Components

The unit is made up of: the Power Supply/Analog Board, the Front Panel, the Basic Engine, the Digital Board, and the Digital Video Input/Output Board. Refer to Figure 14. The DVIO board’s circuitry is contained on the Digital Board of the VN04 product.

Block Diagram Descriptions

Power Supply The Power Supply is a SMPS using Hot Ground on the primary side of the transformer. There is no MAINS power switch. It is operating when AC is applied. It supplies power to: the Analog Board, the Digital Board, the Basic Engine, and the Front Panel..

Front Panel Display This module contains a microcomputer that doubles as a fluorescent display driver. It receives the IR inputs and the keyboard inputs. It communicates the user input from the Keyboard and IR

Receiver via the I2C Bus to the Microcomputer on the Analog Board.

Basic Engine (BE) This consists of the Mechanism and Servo control PCB. The Mechanism is essentially the same as a DVD with the exception of the Optical Pickup Unit, OPU. The OPU has a dual direction signal and light path, one for the write signal and one for the play signal. The OPU has three ICs mounted on it for processing laser signals. These include: the Laser Drive IC or LADIC, the Dvd Recordable Optical Preprocessor IC or DROPPI, and the Non-Volatile RAM or NVRAM to store its electro-mechanical settings.

The Servo controls the Mechanism. It handles the HF signal to and from the OPU. It uses a Microcomputer to control all aspects of the Servo operation. This includes: tray operation, spindle speed, focus, HF preprocessing, and radial positioning of the OPU.

Digital PCB

This module performs many functions. It interfaces between the Basic Engine and the rest of the unit. There are two Digital Boards in the DVDR75. The Product Number is different signifying which Digital Board is in the unit. The one described here is the VN02 product. The functionality and connections are the same. The VN04 product contains the DVIO circuitry, and a different chipset. A separate block diagram follows the Digital Board’s Circuit Description.

During record, it encodes analog video and digital audio into a recordable digital data stream. The Analog to Digital Converter for video is part of a Video Input Processor, VIP, that supplies the MPEG2 Encoder. The VIP sends parallel digital video to the EMPRESS and the VSM. The Empress is the MPEG2 Encoder. It receives video from the VIP and audio from the Analog Board. The Audio is A/D converted on the Analog Board. The EMPRESS is a microcomputer. It has its own SDRAM. It supplies MPEG2 data to the VSM, Versatile Stream Manager. Using sync from the Digital Video coming from the VIP, the VSM converts the signal into an I squared S serial signal. The serial data is sent to the BE to be recorded on the disc.

During playback, the MPEG2 Decoder receives its I squared S input directly from the BE. It decodes the data stream into analog Video and digital Audio. Both are sent to the Analog Board. Digital Video is provided to the Line Doubler. The Line Doubler receives 11 bit digital YUV. The Line Doubler produces progressive scan digital Y/U/V that goes to the Digital to Analog Encoder. Y, Pr, and Pb are sent to the Analog Board.

The Host Decoder is the Master of the I squared C bus that provides communication between the Microcomputers: Empress, VIP and the Line Doubler. The VSM Communicates to the System Control Microcomputer Via UART1. UART2 provides communication between the Digital Board and the DVIO Board. EMI uses Flash memory to provide the Boot up sequence and the operational firmware. Updates can be loaded to

Figure 14 – O

enhance operation of the unit. At present, the update disc is version 6.1.

Analog PCB This module contains: the Power Supply, the System Control Microcomputer, all the A/V inputs and outputs including a Tuner/RF Modulator. Source selection and output type are controlled by the microcomputer. The microcomputer controls many functions throughout the unit including: Power up, user input, input/output selection, the Tuner, the D/A, and A/D functions of the Audio. It also controls the Fans.

Input selection is an important function performed by the analog board. The user selects between: External 1 and 2, DVIO, Tuner Video, and Front Panel jacks.

Audio processing is performed on the Analog Board. The Audio signal coming from the Tuner has a separate demodulator. The Multi System Processor, MSP, demodulates the audio and sends the signal to the Routing Switch. The MSP selects between Tuner Audio and the DVIO Audio signals. The selected audio is sent to the A to D Converter. Digital Audio is supplied to the Digital Board for recording.

DVIO PCB The Digital Video Input Module provides IEEE 1394 translation to the DVD recorder. It separates the Digital Video and Audio. The Digital Audio is decoded and sent as Analog Audio to the Analog Board. Digital Video (DV) is supplied to the Video Input Processor on the Digital Board. The DVIO board communicates with the Digital board via UART2.

Power Supply

This unit uses a Switch Mode Power Supply, SMPS. It operates whenever ac is applied. A MOSFET transistor turns On and Off in an oscillator fashion, driving a transformer. The primary half of the supply uses a Hot Ground. The primary side of the circuit provides drive and coarse control of the power supply. The secondary side of the circuit rectifies and filters the output of the transformer to produce many output voltages. It uses a cold ground, signal ground system. The output is monitored for precise regulation. The 5Vdc is supplied to the anode of the Optic Coupler’s diode and fed to the Shunt Regulator. The regulation path includes an Optic Coupler to accommodate the different grounding systems.

Circuit Description

AC Input Circuit The AC input is rectified by diodes 6301, 6302, 6305, 6306, and filtered by C2309. Refer to Figure 15. The voltage on C2309 is approximately 155V. It can vary from 150V to 160V, depending on the AC input voltage.

Start Circuit The start up of this power supply is mostly contained in IC7313. The Drain supply voltage goes to Pin 8 of the IC. The running supply for the IC is Pin 1 of the IC. The Supply Control provides a measured supply to the VCO and the Driver for start up. The power supplied is not enough to keep the unit operating. If the supply does not operate and supply Pin 1 with operating power, the unit stalls.

When the power plug is connected to AC, the MOSFET 7307 will start conducting when the gate voltage reaches the threshold value. A current starts to flow in the primary winding of 5300, Pins 7 and 5. While the MOSFET is conducting, energy is building up in the transformer. The current flow through the MOSFET is sensed by R3352, and 3321. When the current level rises high enough to provide a voltage drop on these components, 7307 is turned Off by the driver circuit. Diode 6311 protects the control circuit in

case of failure of the MOSFET by providing an upper-limit to the voltage that can remain on the source of the MOSFET.

Coarse Regulation The positive portion of the signal on Pins 2 and 3 will be rectified via D6316, charging C2325. In time, the voltage on C2340 will reach 9 to 13Vdc. This value depends on the value of the Mains voltage and the load. This is also used as a regulation supply for the optic coupler IC7314.

The control circuit consists of a VCO, the Driver, an Op Amp and Gate that are fed by the sensing resistors, 3352 and 3321, and C2340. This circuit controls the conduction time and the switching frequency of the MOSFET. It switches Off the MOSFET as soon as the voltage on the source of 7307 reaches a certain value.

Demagnetization or complete magnetic field collapse is desired before the next drive signal is applied to the MOSFET. This improves efficiency by reducing the power necessary to build a magnetic field in the transformer. Pin 4 is the Demag input. When Pin 4 is near 0Vdc, the gate is enabled, allowing the next oscillation to occur.

Secondary Rectifier/Smoothing Circuit There are six Rectifier/Smoothing circuits on the secondary side. Each supply voltage depends on the number of windings in the transformer. From these circuits, several voltages are derived.

Precise Regulation The 5VREG is monitored for regulation. The regulation circuit consists of an Optic-Coupler, 7314, a shunt regulator, 7315, and a voltage divider network. The Optic-Coupler isolates the Hot Ground on Pin 2 of 7313 from the Cold Ground voltage on 7315. 7315, a Shunt Regulator, has two component characteristics. It is a very stable and accurate reference diode and a high gain amplifier.

7315 will conduct from cathode to anode when the 5VREG is rises higher than the 5Vdc. The 5VREG is divided down to a 2.5V reference voltage. If the 5VREG and subsequently the reference voltage is lower, the cathode current is

almost zero. The cathode current flows through the LED of the Optic-Coupler, controlling the current through the transistor portion of the OpticCoupler. The collector current of 7314 will adjust the feedback level of the error voltage at Pin 3 of

7313.

There are standby and switched supplies. The 5VSTBY, 12VSTBY, 5NSTBY, 33VSTBY and the VGNSTBY supplies are always present when AC is supplied. The VGNSTBY supply ia a -33Vdc dedicated to the Front Panel Fluorescent Tube as a grid supply. The 5SW, 8SW, 12V, 5V, and 3V3 supplies are switched.

The STBY control voltage switches On the 5SW and the 8SW. As part of the first layer of Power Up, the System Control Microcomputer pulls the STBY line Low. This removes bias to 7308 and

7321. This allows the standby supplies to bias 7319 and 7320 On. These supplies go to the RF Unit, the Sound IF and the Input Matrix.

The ION control voltage turns the unit On and Off. When the user turns the power On, the ION control voltage goes Low, turning 7306 Off. The 33VSTBY supply is allowed to turn On 7318. The switched 12V becomes available. The Switched 12V switches On the 3V3 and the switched 5V supplies. The 3V3 and 5V supplies are regulated by shunt regulators, controlling MOSFETs.

Overcurrent Protection Circuit When the output is shorted, the current through the FET will produce a large voltage drop across the source resistors of the FET. When Pin 5 is elevated, the Op amp’s output is low, disabling the output of the Driver. This switches Off the drain current of the MOSFET, 7307. The start circuit will try to start up the power supply again. If the short still exists, the complete start and stop sequence will repeat. The power supply is in a hiccup mode and is ticking.

Overvoltage Protection Circuit If the regulation circuit does not function due to an error in the control loop, the regulated output voltage will increase. This overvoltage is sensed

Figure 15 - Power Supply Circuit

on the hot ground side of the transformer at Pins 2 and 3. When an overvoltage is detected, the Demag circuit will activate the inverter. The power supply will be shutdown until the voltage returns to zero. it will then try to restart.

The IPFAIL signal is used as a Power Fail measurement signal. During normal operation, 7310 is biased On by 6315 and 6312. When power is interrupted that Bias is removed prior to the Filter capacitors draining off their charge. 7310 turns Off, allowing the 5VSTBY to turn On 7311. The IPFAIL goes low. This signal goes to the System Control Microcomputer and Mute circuits.

Microcomputer

The Microcomputer, IC7804, is a 16-bit processor with internal ROM and 4kB RAM. It uses External RAM, IC 7803, and Flash, IC 7805. It is mounted on a Sub Board soldered into the Analog Board. Refer to Figure 16. The System Clock operates at

24MHz. It uses an I2C interface to communicate with the other Microcomputers in the unit. The clock rate is approximately 95kHz. The Reset Pin is high during normal operation. The microcomputer uses non-volatile EEPROM, 7805. The EEPROM stores data specific to the device, such as the AFC-reference value, clock-correction-factor, etc.

Power up

7804 controls power up of the unit. There are three layers to the power up sequence. The first layer involves the Analog Board and the Front Panel. The second layer involves the Digital Board and the BE. The third involves the Front Panel and the Analog Board.

The first layer controls the first set of switched supplies. After the System Control Microcomputer receives its reset, the STBY control voltage goes Low to turn On the first set of switched supplies, the 5SW and the 8SW. It

communicates on the I2C bus initializing the RF Unit, the Sound IF, and the Input Matrix ICs. If they respond properly, it then communicates on

the I2C to the Front Panel Microcomputer. If the Front Panel Microcomputer responds properly, the ION control voltage goes Low.

The second layer occurs when the ION switching voltage goes Low. It comes from the System Control Microcomputer. The ION control voltage passes through the Digital Board to the Power Supply and turns On a second set of switched voltages. These include the 3.3Vdc supply. The

3.3Vdc supply is the main B+ to many of the microcomputers throughout the unit. The System Control Microcomputer then sends out the IReset signal to 7902 on the Digital Board. This IC produces a delayed Resetn signal line for

7200. 7200 activates its I2C and provides several reset and initialization signals for the Digital Board, DVIO, and the BE. They all go through a self test. If the self test succeeds, the VSM communicates through UART1 that the system is operating, and the unit can enable the Front Panel to accept a response. The Front Panel Microcomputer then places four dashes on the Front Panel Display. ION goes High placing the unit in Standby, waiting for keyboard input. This normally takes 6-8 seconds. The System Control Microcomputer allows 10 seconds for the UART1 response. If it does not come, the unit goes into sleep mode, and will not accept keyboard input.

When the Front Panel Microcomputer receives a keyboard response, it communicates that action to the System Control Microcomputer to switch back On the second layer of switched voltages.

The System Control Microcomputer controls the operation of the entire unit. It uses UART1 for communication with the Microcomputers on the

Digital Board. It uses the I squared C Bus ,I2C to communicate with devices on the Analog Board. It receives composite sync from the Selected video source. This is to determine that a good signal source has been selected before the unit is allowed to record.

Figure 16 - System Control Microcomputer

Front Panel

The main elements of the Front Panel are the microcomputer, 7103, the Display Tube, and the keyboard. Refer to Figure 17. 7103 is an 8-bit microcomputer fitted with 96kB ROM and 3kB RAM and is responsible for the following functions:

Fluorescent Display driver

Monitoring the keyboard matrix

Communicating with the System Control Microcomputer

Decoding the remote control commands from the infrared receiver, 7107.

Activation of the display

The Fluorescent Tube operates using a grid and segment scanning matrix. AC is supplied by a switching regulator consisting of 7106, 7108, and

7109. A squarewave is produced by the Microcomputer on Pin 19. The Signal is amplified by 7109 and supplied to the Push/Pull output Amp.The signal passes through 5104 going to the tube. With AC supplied, the microcomputer scans the elements in the tube to determine what segments light up. The system clock is generated with the 8MHz crystal, 1100.

Keyboard Matrix

There are 6 keys on the display board and 1 on the Standby board. A resistor network is used to generate a specific voltage value, depending on the key pressed, via the resistors 3300, 3103, 3104, 3106, 3108, 3110, and, 3130. This RTL data (voltage Level) is sent to 7103 on Pins 36 and 37. Pressing keys simultaneously may lead to undesired functions.

Communication with the System Control Microcomputer occurs on a I Squared C bus, SDA and SCL. The Front Panel receives standby supplies, so it is always live when AC is suppled

to the set. The System Control Microcomputer Hosts the I squared C Bus. The System Control resets and initiates the I squared C bus. The Front Panel Microcomputer resets simultaneously and communicates to the System Control Microcomputer that It is operating. The push buttons and IR receiver are then monitored.

IR Receiver

The IR receiver, 7107, contains a bandpass amplifier as well as a photo-diode. The photodiode receives approximately 940nm infrared pulses. The pulses are amplified and demodulated. On the output of the IR receiver, 7107, is a pulse sequence at TTL levels. The IR signal appears on Pin 20 of 7103.

The Front Panel contains a Thermal Sensor. It is a temperature coefficient resistor. As the temperature rises, so does the resistance. This voltage is sent to the Fan Control Circuit.

The Record LEDs are controlled by the Front Panel Microcomputer. 7105 and 7112 are the LED drivers. Pin 3 of the microcomputer goes low to turn on the lights. That turns On 7112 which in turn turns On 7105. 7105 pulls current through the diodes illuminating them.

Figure 17 - Front Panel Circuit

Analog Processor Board

The Analog Board controls all analog input/output selection, and routing. It houses the System Control Microcomputer. The System Control Microcomputer controls the routing and other functions on the board. One of its other main functions is to control power and initialization of the unit. It implements Keyboard instructions. The board has the Optical Audio Out and the Coax Digital Audio Output circuits. It controls the Tuner. The Audio D/A and A/D conversion is performed on this Board. It contains the Fan Control circuit and houses the first Reset circuit for the System Control Microcomputer.

There are three circuits that can Mute the audio. The Digital Board produces the D_KILL signal. There is a power fail circuit, which is necessary to mute AUDIO when power is lost, IPFAIL. The System Control Microcomputer produces the Kill signal.

Tuner/RF Unit

The Tuner is part of and RF Unit. It contains the Tuner, An RF Modulator and the Demodulator/IF. The Tuner is capable of receiving 125 channels, and is cable ready. Refer to Figure 18. The RF connections on the back are part of the Tuner, RF Modulator. The RF Unit receives two supply voltages, 33Vdc and SW5Vdc. The channel selection information is communicated via the

I2C lines. The output channel is selected by CSW_SSW control voltage. Video is output from Pin 24. 7700 buffers the signal before it goes to Input Matrix. The RF Unit does not perform audio demodulation. The audio signal leaves the RF Unit as Sound IF, from Pin 15 of the RF Unit. The Digital Board’s output video, D_CVBS goes to the RF Unit for the RF Modulator to output the signal on channel 3 or 4. The audio signal returns to the RF Unit on Pin 2 to be used by the RF Modulator. The AFT signal comes from the Microcomputer.

Audio Demodulator

The Sound Processor, 7600, demodulates the Audio. MPS means Multi System Processor. The

I2C bus controls its operation. It uses two power supplies, the 5Vdc and the 8V Switched. IC 7600 has its own oscillator on Pins 5 and 6. Amplitude and bandwidth of the demodulated audio signals

can be determined in 7600 using the I2C bus. It sends analog audio back to the RF Unit from Pin

26. The audio coming from the Digital Board, ARDAC and ALDAC, go into the Sound IF. The

I2C bus controls what Audio is output, the Tuner Audio, or the Digital Board’s output. The Audio signal output from the MSP is available at Pins 30, AFER, and 31, AFEL. 7600 controls the audio input selection via RAS1 and RAS2 switching voltages. They go to the Input Selection Switch, 7501.

7419 and 7420 perform level matching between the 5V serial clock and data lines of the Tuner and Demodulator to the 3.3V levels coming from the Microcomputer.

Input Matrix

The A/V I/O switching is controlled by a switch-

ing matrix, 7408. It is controlled via the I2C Bus. The Matrix controls what source will be supplied to the Digital Board. There are several choices: Tuner Video, External 1(Y/Pr,Pb), External 2 Video, and Front Video. In addition there are 2 Y/C inputs. All switches have 6 dB amplification on the outputs. The Matrix is not responsible for handling the Y/Pr,Pb. It goes directly to the Digital Board when present.

The user selects what source is to sent to the

Digital Board on Pin 9 of 1947. The I2C Bus communicates this data to the Matrix IC. The selected source comes out Pin 21 of 7408. The Matrix communicates channel selection control for the RF Unit on Pin 44.

The unit can receive a 16 by 9 input using the Y/C inputs. The Microcomputer must detect this format and communicate it to the Digital Board.

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