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Siera SG 1420N Service Manual

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SERVICE MANUAL
SERVICE MANUAL
CTS-AA
CHASSIS

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Summary of Contents for Siera SG 1420N

  • Page 1 SERVICE MANUAL SERVICE MANUAL CTS-AA CHASSIS...

  • Page 2: Table Of Contents

    CONTENTS Page 1.- Technical specifications 2.- Connection Facilities 3.- Mechanical instructions 4.- Oscillograms 5.- Print board layout 6.- Electric Scheme 7 - 11 7.- Circuit description 7.1 Small signal processing 7.2 RGB ampliers 7.3 Deflection 7.4 Sound amplifier 7.5 Power supply 7.6 Microcontroller/Text 8.- Electrical adjustments 9.- Safety instructions...

  • Page 3: Technical Specifications

    1. Technical specifications CHASSIS CTS - AA Mains voltage : 220 - 240 V ± 10% AC; 50 Hz (±5%) Power cons. at 220V~ : 35W (14''), 50W(20''/21''), 5W (stand by) : 75 S - coax Aerial input impedance Min. aerial input VHF : 30µV Min.

  • Page 4: Mechanical Instructions

    3. Mechanical instructions For the main carrier two service positions are possible (3.1). A: For faultfinding on the component side of the main carrier. B: For (de) soldering activities on the copper side of the main carrier. Position A can be reached by first removing the mains cord from it's fixation, then loosen the carrier lips (1) and then pulling the carrier panel (2) for approximately 10cm.

  • Page 5: Oscillograms

    4. Oscillograms...

  • Page 6: Print Board Layout

    5.- PRINT BOARD LAYOUT...
  • Page 7 6.- Electric Diagram 1015 D6 3281 F3 1032 G8 3284 K2 1033 F8 3285 K2 1137 B7 3286 L2 1272 H3 3287 K2 2010 D7 3288 K3 2011 D7 3289 K3 2013 D8 3291 K3 2014 D8 3294 L3 2015 H6 3330 E2 2016 H6 3331 F2...
  • Page 8 6.- Electric Diagram 2204 C6 3433 G3 2208 E3 3434 H3 2209 D3 3440 M7 2217 D6 3442 M6 2230 F6 3444 L7 2402 G7 3445 L5 2403 H6 3449 M3 2404 I8 3451 L6 2405 I7 3455 K7 2406 I5 3456 K6 2407 H5 3457 J5...
  • Page 9 6.- Electric Diagram 1001 B7 6852 E4 2001 B8 6853 D4 2002 B6 6854 D4 2005 D7 6855 D4 2006 C7 6856 D4 2090 C8 6857 D5 2091 D8 7187 J4 2092 D8 7187 K6 2179 K3 7875 B5 2182 K3 7876 D2 2184 K4 9102 L6...
  • Page 10 6.- Electric Diagram 1500 C1 3525 C3 1540 I4 3527 G4 1541 H2 3528 G4 2500 D2 3570 J3 2502 F2 3571 K3 2503 E2 3573 K3 2504 F2 3574 I3 2505 F2 3575 J5 2506 H5 3576 J3 2507 E2 3577 I3 2508 F4 5500 D2...
  • Page 11 6.- Electric Diagram 1679 G3 3687 K3 1685 F2 3691 B2 2149 E2 3692 B2 2600 D3 3696 J8 2602 C7 6149 E3 2610 D7 6602 C7 2611 D8 6663 J7 2636 K7 6691 C2 2641 K3 7600 H5 2648 L7 7605 C7 2651 B3 7657 E2...
  • Page 12 STV2246: STV2248: Figure 7.1 TV Processor block diagram...

  • Page 13: Circuit Description

    7.- CIRCUIT DESCRIPTION 7.1 SMALL SIGNAL PROCESSING (Diagram A) The small signal is processed by IC 7015 (STV2246 for Pal sets, STV2248 for Pal/Secam sets), including IF detection, video processing, chroma decoder, RGB , sync processor and sound decoder. The ICs STV2246 and STV2248 are fully controlled by I2C bus and their block diagram can see in fig.
  • Page 14 - Luminance processor: CVBS coming from video switches is internally applied to luminance processor, which is composed of chrominance trap filter, luminance delay line and peaking circuits. Sharpness control modifies peaking by I2C. - Black stretch circuit (pin 21): This feature of the picture is fixed (not adjustable). Black stretch capacitor 2250 is connected to pin 21.

  • Page 15: Rgb Ampliers

    Note: The set do not start up if protection voltages are activated (Vpin 49 > 2.5V or Vpin46 < 1V) - Hor. sync. separator: Fully integrated sync. separator with a low pass filter, slicing level at 50% of the synchronized pulse amplitude.

  • Page 16: Sound Amplifier

    7.3.2 Line deflection The final line transistor is driven by the transformer 5441, whose primary winding is driven by the transistor T7440 connected to the line drive output of IC7015 (pin 48). The horizontal deflection stage is carried out in a conventional way, with the deflection transistor (T7445) and line transformer (5445).
  • Page 17 - Output regulation (pins 1, 2, 8): IC7514 stabilizes output voltage by controlling T-on and so the frequency and the duty cycle. Start pulse to T7525 is determined by pin 8 circuit (see fig 7.5). Then a sawtooth voltage V2 is generated at pin 2. Stop pulse to T7525 is produced when V2 reaches Vcont. Output control is done by the following way: If output is higher, V1 is higher, Vcont is lower, T-on and output will be reduced.

  • Page 18: Microcontroller/Text

    7.6 MICROCONTROLLER/TEXT (Diagram E) The CTS-AA chassis is designed to accept 2 different microcontrollers: SAA5531 for TXT models and SAA5541 for no TXT. Both microcontrollers are mounted in the same position (7600), and the associated circuitry is the same. The ROM of the ICs contain an specific program that assures all the functions of the appliance, including 2 menus, one to control the set (see Instructions Manual) and another for Service Mode (see Service Instruct.

  • Page 19: Electrical Adjustments

    8.- ELECTRICAL ADJUSTMENTS 8.1 Service mode The signal processor IC7015 (STV2246 or STV2248) is fully controlled by I2C for the µC IC7600, so that the most of adjustments of the set can be made by service menu. - Enter in Service mode: There are 2 ways to enter in Service mode - By a short circuit between pin 7 of microcontroller ( IC7600 ) and ground while the set is starting up.
  • Page 20 8.3 AFC IF Carrier frequency can be adjusted in automatic or manual way. It is recommended the automatic way. There is an adjusting symbol for AFC on the top of the service menu consisting of a double arrow (><). If only one arrow appears (<) or (>) AFC should be readjusted to reach double arrow (><).
  • Page 21 8.5.3 White checking: - Connect pattern generator containing grey scale - Adjust the set to normal operation and reduce the saturation control to minimum. - Allow the set to warm up about 10 minutes and check visually if the grey scale has correct colour. - If not, enter to Service menu and adjust G and B gain (items 14 and 15) until a desired grey is obtained.

  • Page 22: Safety Instructions

    9. Safety instructions, maintenance instructions, warning and notes Safety Instructions for Repairs Warnings 1. Safety regulations require that during a repair: In order to prevent damage to IC's and transistors any flash-over of - The set should be connected to the mains via an isolating the EHT should be avoided.

  • Page 23: List Of Abbreviations

    10. List of abbreviations µC Microcomputer µP INT/EXT Switching signal from µC to TS7876 and TS7877 (diagram C) making together with pin 8 of SCART connector the INT/EXT switching signal; "low" for internal, "high" for external Alternating Current Automatic Frecuency Control Automatic Gain Control Amplitude modulation Automatic Peak Regulation...
  • Page 24 11.2 Electromechanical CTS-AA CHASIS 11. REPLACEMENT PARTS LIST CTS-AA CHASIS 11.1- Electrical TABLE 11:...
  • Page 25 11.3 Mechanical, chasis and switches CTS-AA CHASIS NG-BLACK BL-WHITE GR-GREY MA-IVORY GO-DARK GREY POSITION SCREEN TV MODEL COLOUR VE-GREEN RS-PINK RJ-RED AZ-BLUE PL-SILVER HOW TO ORDER EXAMPLE: FRONT CABINET OF TV700TX COLOUR BLUE: A * 14 * TV700TX * AZ...

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