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Toshiba_CV27D48 Chassis N4FV_training_manual


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                                                                  CONTENTS
SECTION I N4VF CHASSIS OVERVIEW
  1. N4VF CHASSIS (CV27D48) FEATURES ..................................................................................................1-2
  2. SPECIFICATIONS .......................................................................................................................................1-2
  3. N4VF CONFIGURATION ..........................................................................................................................1-3
      3-1. Layout ..................................................................................................................................................1-3
      3-2. Service Position....................................................................................................................................1-3
  4. BLOCK DIAGRAM ....................................................................................................................................1-4

SECTION II POWER SUPPLY CIRCUIT
  1. POWER SUPPLY BLOCK DIAGRAM ....................................................................................................2-2
      1-1. Power Supply Overview .......................................................................................................................2-3
      1-2. Main Switching Circuit .......................................................................................................................2-3
      1-3. Voltage Regulator/Controller IC ..........................................................................................................2-4
  2. TROUBLESHOOTING...............................................................................................................................2-4
      2-1. Troubleshooting Flow Charts ..............................................................................................................2-5
           Flow Chart 1 - TV Does Not Turn On .................................................................................................2-5
           Flow Chart 2 - No High B+ .................................................................................................................2-6
           Flow Chart 3 - High B+ Supply in Shut-down ....................................................................................2-7
  3. POWER LINE TIMING CHART ..............................................................................................................2-8

SECTION III SYSTEM CONTROL
  1. SYSTEM CONTROL OVERVIEW ...........................................................................................................3-2
      1-1. Clock/Reserve Function .......................................................................................................................3-2
      1-2. Channel Selection Functions (PLL-IC control) ...................................................................................3-2
      1-3. Other Functions ...................................................................................................................................3-2
  2. MAJOR FEATURES IN THE CHANNEL SELECTION SYSTEM ......................................................3-2
  3. LOCAL KEY DETECTION METHOD ....................................................................................................3-8
  4. SERIAL CONTROL ....................................................................................................................................3-9
      4-1. Channel Selection ................................................................................................................................3-9
      4-2. Video/Audio Adjustment Control ......................................................................................................3-10
      4-3 . Non Volatile Memory Control ......................................................................................................... 3-11
  5. DATA COMMUNICATION BETWEEN VCR AND MAIN MICROCOMPUTERS ........................3-13
      5-1. Serial Transfer Timing Chart ............................................................................................................3-13

SECTION IV SIGNAL PROCESSING (A/V Selection & Y/C Separation)
  1. SIGNAL FLOW OVERVIEW ....................................................................................................................4-2
  2. A/V SWITCH CIRCUIT .............................................................................................................................4-2
       2-1. Record Signal .......................................................................................................................................4-2
       2-2. Monitor Signal .....................................................................................................................................4-2
       2-3. Audio Mode Switch .............................................................................................................................4-4
  3. Y/C SEPARATION CIRCUIT ....................................................................................................................4-5
       3-1. Comb Filter Circuit ..............................................................................................................................4-5
       3-2. XZ01 I/O Signals .................................................................................................................................4-5
  4. TROUBLESHOOTING...............................................................................................................................4-6
       4-1. Common Items for TV, EXT. & VCR .................................................................................................4-6
            4-1-1. No Picture (VCR Records) ........................................................................................................4-6
            4-1-2. No Sound (L&R channels, VCR Records Audio) .....................................................................4-7
            4-1-3. Troubleshooting A/V Switch (in Audio and Video) .................................................................4-8

SECTION V VCR DECK TROUBLESHOOTING
  1. TROUBLESHOOTING...............................................................................................................................5-2
      1-1. No Play .................................................................................................................................................5-2
      1-2. No Record ............................................................................................................................................5-2
       SECTION I
N4VF CHASSIS OVERVIEW
       (CV27D48)




          1-1
1. N4VF CHASSIS (CV27D48) FEATURES
The N4VF (CV27D48) chassis is a combination TV and              (6) A MTS/SAP circuit, which allows stereo/SAP
VCR which uses a derivative of the N3SL TV chassis in               reception and recording;
the TV section and a V3 deck in the VCR section. The            (7) An A/V input terminal and variable audio output
features of the CV27D48 include:                                    terminals; and
(1) A 27 inch full square tube (FST);                           (8) A V3 VCR section with specifications similar to the
                                                                    M650 VCR.
(2) A simple and easy operating system that provides
    operating procedures and displays erroneous                 Further specifications and features of the CV27D48
    operations on the screen for both the VCR and TV;           Combo are outlined in the chart below. Detailed service
                                                                information is found in Service Manual 020-9409.
(3) An analog clock system to set the clock and OSD
                                                                Training Manual NTDVCR05 contains a detailed
    programming of up to six events per month;
                                                                explanation of the V3 VCR.
(4) A 181 Channel synthesizer tuning system;

(5) A GLASS comb filter for Y/C separation (used to
    reduce dot interference and cross color noise);

2. SPECIFICATIONS
Major specifications are as follows.

                        Type name                                                   CV27D48
  Power supply                                          AC 120V, 60 Hz
  Remote control                                        40 key type remote transmitter
                                                        UP/DN key to switch menu, PROG/ADV/UP/DN key to switch
                                                        timer recording.
                                                        VCR control key, etc.
  Dimensions                                            Width        : 680 mm
                                                        Height       : 651.5 mm
                                                        Depth        : 498 mm
  Weight                                                40.5 Kg
  Speaker                                               2.4" x 4.7" oval speakers
  Audio output                                          3W x 2
  A/V input terminal                                    Video        : 1 V(p-p), 75 ohms, negative sync,
                                                        Audio        : 150 mVrms, more than 47 K ohms
             Signal system                              Standard NTSC
             Recording/playback system                  Recording :           format (SP, SLP)
                                                        Playback :            format (SP, LP, SLP)
             Cassette                                   Video cassette with          mark
   VCR
             Tape speed                                 SLP : 11.1 mm/s,       SP : 33.4 mm/s
             Video recording/playback time              SLP : 480 minutes, SP : 160 minutes (When T-160 video
                                                        cassette is used)
             Audio frequency range/dynamic range        Frequency range       : 20 Hz ~ 20 kHz
             (Hi-Fi)                                    Dynamic range         : 90 dB




                                                         1-2
3. N4VF CONFIGURATION
3.1 Layout
The orientation of the N4VF chassis
is shown in Figure 1-1. The chassis is
divided into two parts, the TV
Chassis and the VCR Deck. Power,
control, and Audio/Video to and                                               INTERCONNECT CABLES
from the VCR Deck are provided by
three interconnect cables. This
configuration allows easy access to
either the VCR Deck or the TV
Chassis.
3-2 Service Position                       TV CHASSIS
The VCR Deck is placed in the
service position in the following             VCR DECK
manner (see Figure 1-2). Disconnect
the three interconnect cables form the
deck. Remove the two screws
that fasten the VCR deck into                            Figure 1-1 N4VF Chassis Configuration
the cabinet. Carefully pull the deck out of the cabinet and      board. Reconnect the cables from the TV chassis to the
place it on the service bench. Then remove the shield to         VCR Deck. See Service Manual 020-9409, pages 8 and 9,
access the top of the deck. Take the deck out of the deck        for further disassembly instructions.
frame to access the bottom of the VCR's main circuit




                                         Figure 1-2 VCR Deck Service Position



                                                          1-3
4. BLOCK DIAGRAM
The block diagram of Figure 1-3 shows the main circuits            the TV Chassis section (HV, Deflection, and Video Driver
of the CV27D48. The TV chassis incorporates mainly five            circuits) to be off while the VCR Deck is in the record
boards: the Main Board, the A/V Switch Board, the V/C/D            mode. In this case, power must be supplied to the tuner,
Board, the CRT Board, and the Key Control Board. The               IF, and AV Switch circuits. Power is also constantly
TV Tuner (H001) and TV IF/MTS Module (H004) are                    supplied (as long as ac is supplied to the set) to the system
also located on the Main Board. The VCR Deck (not                  control circuits.
shown) contains the VCR processsing circuits. Three
                                                                   Since the VCR Deck does not contain its own tuner, the
interconnect cable assemblies are used to interface the
                                                                   audio and video signals are selected by the AV Switch
VCR Deck to the TV Section. One is used for power, the
                                                                   circuits located on the AV SW Board. Thus, the video
other for the Audio/Video (A/V) signals, and the third for
                                                                   signal displayed on the screen and the selected audio are
system control communication.
                                                                   also the Record Signals (REC. SIG.) that are routed to the
There are two switch mode power supplies located on the            VCR Deck. During playback, the composite video play
Main Board. Other sources are developed on the VCR                 signal (PLAY SIG.) from the VCR is routed to the video
Main Board (a detailed description of the power supply             processing circuits and the audio channels are routed to
follows in Section II). The separate power supplies allows         the speakers via the audio processing circuits.
 E1
 To VCR DECK




                                          Figure 1-3 CV27D48 Block Diagram




                                                             1-4
     SECTION II
POWER SUPPLY CIRCUIT




         2-1
1. POWER SUPPLY BLOCK DIAGRAM




                Figure 2-1 Combo Power Supply Block Diagram



                                    2-2
1-1. Power Supply Overview                                         over-load condition. If shutdown of the High B+ Supply
                                                                   occurs, the VCR Record Function will continue
The CV27D48 contains two independently controlled
                                                                   uninterrupted.
switch mode power supplies as illustrated by the Block
Diagram of Figure 2-1. The Main SMPS develops the                  1-2. Main Switching Circuit
32Vdc, 14Vdc, and the 6.3Vdc sources via the secondary             The switching circuit for the Main Power Supply is shown
rectifier/filter circuits of T830. Voltage regulation is           in Figure 2-2. The Main Supply is active as soon as ac is
provided by IC831, D839, and Q830. Additional sources              applied. Thus, Vcc is supplied to the microcomputers as
derived from the 14V and 6.3V sources by the                       long as ac is available to the set.
Controller/Voltage Regulator IC (IC831) include, the
                                                                   When ac power is applied to the set, a dc voltage is
On-Off 9Vdc, the Ever 5.6Vdc, and the Ever 5Vdc for the
                                                                   supplied to Pin 2 of Q830 via R831 and R834, foward
TV Chassis. The 14V and 6.3V sources are also supplied
                                                                   biasing Q1 (inside Q830). Thus, current flows through Q1
to the VCR Deck as sources and to another Voltage
                                                                   and the primary (NP) of T830. An EMF develops on drive
Regulator/Controller IC (IC821) located on the VCR Main
                                                                   winding ND, which increases the Q1 current. When Q1
Board. IC821 supplies the On-Off 9Vdc, Ever 5Vdc, and
                                                                   reaches saturation, it turns off and an EMF is generated in
the On-Off 5Vdc to the VCR Circuits. A detailed theory
                                                                   winding NS, thus supplying power to the secondary side.
of operation for this power supply is found in the V3
Training Manual, NTDVCR05.                                         When the secondary EMF field fully collapses, D821 is
                                                                   turned off and a reverse EMF is developed from NS to ND.
The other switch mode power supply (High B+ Supply)
                                                                   This is applied to Pin 2 of Q830 via D835 and R834,
develops the 115Vdc and 18Vdc sources. A detailed
                                                                   turning Q1 on. After the initial start-up, the power supply
theory of operation for this power supply is found in the
                                                                   remains in a self oscillation mode.
X90E TV Chassis Training Manual, NTDCTV03. The
115Vdc source supplies power to the HV/Horizontal                  The off time of Q3 and Q1 inside Q830 is controlled via
Deflection Circuit, which develops additional sources,             the feedback components IC831 and D839. This serves to
including the 210V, 27V, FBT 12V, EHT, Focus, and G2.              regulate the 14V source.
The High B+ Power Supply also incorporates shutdown
protection in the event of an over-voltage condition or an




                                                             2-3
1-3. Voltage Regulator/Controller IC                                 2. TROUBLESHOOTING
The LA5611 type IC is a monolithic Integrated Circuit,
                                                                     The power supplies in the N4VF combo chassis are
which contains a primary side error amplifier, a nine volt
                                                                     similar to those used in other Toshiba products. The Main
error amplifier, an ever five volt regulator, an on-off five
                                                                     supply is basically the same as the V3 VCR Power
volt regulator, and a 5.6 volt regulator, as shown by the
                                                                     Supply. The troubleshooting Flow Charts found in the V3
LA5611 Block Diagram of Figure 2-3. Two of these ICs
                                                                     training manual may also apply to the Main power supply
are used in the N4VF Chassis. One is used in the the Main
                                                                     in this chassis. The High B+ Supply is similar to the
Power Supply for the TV chassis (IC831) and one is used
                                                                     power supply in the CF27C40 television chassis. Some
on the VCR Main Board (IC821).
                                                                     areas of the power supply are hot. Always use an isolation
The 9V error amplifier is turned on or off according to a            transformer when troubleshooting the power supplies.
Power On (Low=On and High=Off) signal sent from the
                                                                     During the initial diagnosis, a determination should be
microcomputer. The Power On line for IC831 is from the
                                                                     made as to which supply contains the fault. Some basic
TV Microcomputer, ICA01, Pin 24, and the Power On line
                                                                     hints to determine the location of a fault are as follows.
for IC821 is from the VCR Microcomputer, IC501, Pin
30.                                                                      1. Since the High B+ Supply relies on the Main
                                                                         Supply to turn On, the Ever 5V from the Main Supply
The IC is equipped with a current limiter for the EVER
                                                                         must be available.
5V Regulator. A Temperature Sensing Device (TSD)
                                                                         2. The High B+ Supply contains shutdown circuits
shuts the IC off when the load is short-circuited or if the
                                                                         that may be triggered as soon as the TV section is
temperature rises to 130



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