Technical description and composition of the SHARP LC-20B4E TV, type of panel and applicable modules. The composition of the modules.SHARP
Model: LC-20B4E
Panel: LQ197V3FZ50
Inverter (backlight): KB590DE, KB591DE SB591WJ
MOSFET Inverter: C5886
Trans Inverter: ZA030
Power Supply (PSU): Adapter UADP-0241CEPZ 13V 5A4
MOSFET Power: C5886
MainBoard: KB750DE XB750WJ QKITPB750WJN2
IC MainBoard: DPS 9450A A1, 24C32, VPC3230D, BD8120FP
Tuner: DE0347U KB751 SB751MJ
Control: IR: KB752 SB752WJ
Technical Specifications LC-20B4EA
SHARP LC-20B4E
General recommendations for repairing TV LCD
Repair of the SHARP LC-20B4E A TV is advisable to start with an external inspection of all its constituent elements, both internal electronic components and external. Inspection is also subject to body elements, control buttons, screen, connectors and cords. Often, by the external signs and nature of some damage, it is possible to draw preliminary conclusions and determine a further algorithm for troubleshooting. Experienced repairmen are often aware of the causes of the defect and the possible consequences, for example, from ring cracks in the soldering of the leads of the elements, as well as from swollen capacitors or resistors burnt to coal dust and other external indirect signs.
If the LC-20B4E A does not turn on, does not respond to the remote control and the front panel buttons, does not blink bulbs and does not show any signs of operability, most likely in this case the adapter module UADP-0241CEPZ 13v 5A4 is faulty. When diagnosing and repairing the adapter UADP-0241CEPZ 13v 5A4 power supply, first of all, it is necessary to check the fuse, and if it breaks, the power switch C5886 and rectifier bridge diodes should be checked for avalanche (thermal) breakdown.
It should be remembered that in the practice of repair, usually the power keys of N-Fet converters do not fail due to their poor quality and, in such cases, it is necessary to look for the cause that led to a malfunction and provoked a breakdown of the key. Most often, the culprits of the accident are dried electrolytic capacitors or dangling resistors in the primary circuit, or the PWM controller chip itself may be faulty. It is also necessary to check all the semiconductor elements of the stabilization circuit in the primary and secondary circuits.
When using a power factor correction unit (PFC) in the power modules, troubleshooting becomes somewhat more complicated and requires additional experience and knowledge of the device for their operation.
If the SHARP LC-20B4E A does not have an image, but there is sound and the TV is controlled from the remote control, a malfunction in the display backlight nodes is likely. The lamps or the power converter - inverter may be faulty. Often in such cases, when you turn on the TV, an image appears and immediately disappears. First of all, it is necessary to verify the operability of the electrolytic capacitors of the rectifier filter supplying the inverter, and check the LCD lamps by connecting external and obviously serviceable for diagnosis to the connectors.
Often attempts to repair the KB590DE inverter 3 times. KB591DE SB591WJ KB591 2 times. It is hindered by the fact that the diagnosis of the malfunction is complicated by the operation of its protection, which is designed to turn off the inverter in emergency conditions - during depressurization of lamps, breaks or short circuits in high-voltage connections and other emergency situations. Lock protection to localize the defect is popular among repairmen.
It should be remembered that when the protection is turned off, there is always a risk of failure of the power elements of the inverter during diagnosis. After repair, it is necessary to restore all standard converter protection circuits.
In cases of attempts to repair the LC20B4EE motherboard, it is necessary to check the operability of the power supply stabilizers of the microcircuits and, if possible, update the software (software).
Attention to users! Self-repair of the SHARP LC-20B4E A TV without the appropriate qualifications and experience can lead to its complete non-repairability!
schematic / manual -------------------> Sharp LC-20B4E
The appearance of the MainBoard KB750DE is shown in the figure below:KB750DE
Main features of the SHARP LC-20B4E device:
Installed matrix (LCD panel) LQ197V3FZ50.
The KB590DE inverter is used to power the backlight. A transformer ZA030 is installed in the inverter converter. As power elements of the inverter, keys of the type C5886 are used.
To power all the internal nodes of the SHARP LC-20B4E TV, an external adapter type UADP-0241CEPZ 13V 5A4 is used, using power switches of the C5886 type.
MainBoard - the main board (motherboard) is a KB750DE module, using DPS 9450A A1, 24C32, VPC3230D, BD8120FP, and others.
Tuner DE0347U KB751 SB751MJ provides the reception of television programs and tuning to channels.
Additional technical information about the panel:
Brand: SHARP
Model: LQ197V3FZ50
Type: a-Si TFT-LCD, Panel
Diagonal size: 19.7 inch
Resolution: 640x480, VGA
Display Mode: Normally Black, Transmissive
Active Area: 401.28x298.8 mm
Surface: Antiglare (Haze 23%), Hard coating (2H), Reflection 2.0%
Contrast Ratio: 500: 1
Display Colors: 16.7M (8-bit)
Response Time: 10/14 (Tr / Td)
Voltage: 3.3 / 5.4 / 25 / -10.5 / 1.3V (VSH / VLS / VGH / VGL / VCOM)