Technical description and composition of the BBK LT1921S TV, panel type and applicable modules. The composition of the modules.BBK
Model: LT1921S
Chassis / Version: MST9
Panel: HT190WG1-100
Lamp backlight: 4 Lamp CCFL
Inverter (backlight): integrated into PSU
PWM Inverter: BIT3105
Power Supply (PSU): JSI-190411 B
PWM Power: SG6841SZ
MainBoard: RSAG7.820.1264
IC MainBoard: MST9E19B-LF, TDA9886, A25L40, 24C32, 24C04, TDA1517P
Tuner: TDQ-6FT / W126H
Control: RSAG2.908.1169
Technical specifications LT1921S
BBK LT1921S
General recommendations for repairing TV LCD
Possible manifestations of defects
- The BBK LT1921S TV does not turn on and does not show any signs of operability at all. There is no reaction to the remote control and front-panel control buttons.
With such manifestations, in some cases, the JSI-190411 power module is faulty. Then we recommend that you measure its output voltages and, if they are absent, you should check the health of the power switches and rectifier diodes of the converters for a probable short circuit.
In case of breakdowns of semiconductors in the secondary circuits, the converter can usually work abnormally in the short circuit mode, and during short circuit in the power elements of the primary circuit, the mains fuse often breaks.
The breakdown of Mos-Fet keys used in pulsed sources is often caused by malfunctions of other elements, for example, in the power supply circuit of a PWM controller, in frequency-setting or damping circuits, as well as in Negative Stabilization Feedback. PWM microcircuits (PWM) SG6841SZ are usually checked by replacing with new, or obviously working.
- There is no image, there is sound, it responds to the remote control. Or the image may appear for a second when turned on and immediately disappears.
These manifestations can be triggered by a power module, or by defects in the inverter, as well as a distortion of the currents in the lamps due to their uneven wear. If all the electrolytic capacitors of the filter according to the inverter power supply are serviceable, you should make sure that the lamps are working, then you need to check the converter keys and the secondary windings of the transformers.
Sometimes, for diagnostic purposes, inverter protection must be disabled. In such cases, special care must be taken during work, and the protection circuits should be restored immediately after the repair is completed.
- The TV does not turn on, does not respond to the remote control. The indicator blinks or signals standby mode.
Repair or diagnostics of the RSAG7.820.1264 motherboard should begin by checking the stabilizers and power converters needed to power the microcircuits and matrix. If necessary, update or replace the software (software). Sophisticated MB board repair (SSB) is in some cases possible and practiced by repairmen. To do this, check and, if necessary, replace the elements MST9E19B-LF, TDA9886, A25L40, 24C32, 24C04, TDA1517P. BGA chip malfunctions are usually easy to detect by warming up.
In the absence of tuning to the channels of on-air or cable television, you should make sure that the software is correct, as well as in accordance with the ratings of the supply voltage at the terminals of the TDQ-6FT / W126H tuner. It is also necessary to check the presence of pulses of data exchange between the tuner and the processor via the I2C bus using an oscilloscope.
It should be remembered! Attempts to independently repair the BBK LT1921S TV, in the absence of the necessary qualifications and experience, are categorically not recommended and are fraught with negative consequences, up to the complete non-repairability of the device!
FIRMWARE FOR SPI FLASH ---------------> BBK LT1921S MST9, Main: RSAG7.820.1264
Service manual and schematic diagram ------------------> BBK LT1921S Chassis MST9 Hisense LCD19W57
Service Manual with Schematic Diagram 60 pages of 2008 on the LT1921S, LT2621S, LT3221S, LT1919S LT2619S, LT3219S, LT1917S, LT2617S.
The appearance of the MainBoard RSAG7.820.1264 is shown in the figure below:
RSAG7.820.1264
The appearance of the power supply
Main features of the BBK LT1921S device:
Installed matrix (LCD panel) HT190WG1-100.
To power the backlight, a converter is used, combined with a power supply, controlled by a BIT3105 PWM controller.
The necessary supply voltages for all nodes of the BBK LT1921S TV are generated by the JSI-190411 power module or its analogs using SG6841SZ microcircuits.
MainBoard - the main board (motherboard) is a RSAG7.820.1264 module, using microchips MST9E19B-LF, TDA9886, A25L40, 24C32, 24C04, TDA1517P and others.
The TDQ-6FT / W126H tuner provides TV reception and channel tuning.
Additional technical information about the panel:
Brand: BOE
Model: HT190WG1-100
Type: a-Si TFT-LCD, Panel
Diagonal size: 19.0 inch
Resolution: 1440x900, WXGA +
Display Mode: TN, Normally White, Transmissive
Active Area: 408.24x255.15 mm
Surface: Antiglare (Haze 25%), Hard coating (3H)
Brightness: 300 cd / m²
Contrast Ratio: 700: 1
Display Colors: 16.7M (6-bit + Hi-FRC)
Response Time: 1.5 / 3.5 (Tr / Td)
Frequency: 60Hz
Lamp Type: 4 pcs CCFL Without Driver
Signal Interface: LVDS (2 ch, 8-bit), 30 pins
Voltage: 5.0V
BBK LT1921S LCD TV with HT190WG1-100 LCD, 19 "(48 cm) diagonal 16:10 aspect ratio. 300 cd / m² screen brightness is provided by CCFL (EEFL) fluorescent lamps. Maximum brightness to minimum ratio (contrast) ) is 800: 1. It is possible to view images in high quality HD at a resolution of 1440x900 pixels in the standard of graphic decomposition 720p (HD Ready). The input high-frequency or video signal can be processed in analog systems PAL, SECAM, NTSC. Graphic processing and digital signal generation occurs in stand The channels are 480i, 480p, 576i, 576p, 720p, 1080i.
The power of the sound system 3 W (2x1.5 W) provide two speakers. The audio processing system NICAM STEREO is used.
The external interface (communication with other devices) is supported by standard input and output connectors: antenna input (RF), AV, audio x2, S-Video, component, SCART, RGB, VGA, HDMI. An output for connecting headphones is provided. To connect a computer or laptop to this TV model, a VGA (D-Sub 15) connector is used on the TV case, this interface supports resolutions: 640x480, 800x600, 1024x768.
The power consumed by the TV in the operating mode from the network is 45 watts.
Overall dimensions: 468x399x178 mm.
TV Weight: 5.5 kg.
Attention! The BB1 LT1921S LCD TV panel HT190WG1-100 is its most expensive component.
Avoid hitting the glass and exerting pressure on the screen to avoid permanent damage to the LCD panel!