Technical description and composition of the PANASONIC TX-LR42U20 TV, panel type and modules used. The composition of the modules.PANASONIC
Model: TX-LR42U20 TX-L42U20
Chassis / Version: KM09
Panel: LC420WUN (SC) (D1)
Lamp backlight: EEFL
T-CON: LC420WUN-SCD1
Inverter (backlight): 6632L-0620A & 6632L-0621A
Power Supply (PSU): TNP4G478 AA
PWM Power: FA5501AN (C0DBBZG00004), SSC9512 (C0DABYY00025), STR-A6059 (C0DABYY00018)
MOSFET Power: 13N60E (B1DEGR000060), K8A55DA (B1CERQ000060)
MainBoard: TNP4G468 1 A
IC MainBoard: Nand Flash: H27U1G8F2BTR, EEPROM: 24C32, Audio: LV4921
Tuner: ENG37F03KF
Control: Remote: N2QAYB000494, IR: TNPA4834
TX-L42U20 Specifications
PANASONIC TX-LR42U20
General recommendations for TV LCD repair
Possible manifestations of malfunctions
- The PANASONIC TX-LR42U20 does not turn on, the indicators on the front panel do not light or flash. The TV does not respond to the control buttons and the remote control.
In some of these cases, the fault is detected in the TNP4G478 power supply module. It is necessary to make sure that its output voltages are present and, if they are completely absent, check the power switches (13N60E (B1DEGR000060), K8A55DA (B1CERQ000060)) and rectifier diodes for a possible short circuit.
In case of breakdowns in the secondary circuits, the converter, as a rule, can operate in an emergency mode in the short-circuit mode, and in the event of a short circuit in the power elements of the primary circuit, the mains fuse is usually cut off.
Mos-Fet keys used in switching power supplies usually fail due to a malfunction of other elements, which can disable it in key mode, or provoke an excess of the maximum current or voltage values. These can be circuits supplying a PWM controller, damper or frequency setting circuits, or OOS (negative feedback) elements in the stabilization circuit. PWM controllers (PWM) FA5501AN (C0DBBZG00004), SSC9512 (C0DABYY00025), STR-A6059 (C0DABYY00018), in the absence of external damage and short circuit between the terminals, are checked by replacing them with known good ones.
- There is no image, there is sound, it reacts to the remote control. Or the image may appear for a second when turned on and disappear immediately.
These manifestations can be provoked by the power module, or by defects in the inverter, as well as by the skew of currents in the lamps due to their uneven wear. If all the electrolytic capacitors of the filter for the power supply of the inverter are in good working order, you should make sure that the lamps are in good condition, then you need to check the converter keys and the secondary windings of the transformers.
Sometimes it is necessary to disable the inverter protection for diagnostic purposes. In such cases, special care must be taken during work, and the protective circuits must be restored immediately after the repair is completed.
- The indicator blinks or is on constantly, the TV does not turn on, does not respond to the remote control.
Repair or diagnostics of the TNP4G468 motherboard should begin with checking the stabilizers and power converters necessary to power the microcircuits and the matrix. If necessary, you should update or replace the software (software). In some cases, to repair the MB (SSB) board, it may be necessary to replace chips - Nand Flash: H27U1G8F2BTR, EEPROM: 24C32, Audio: LV4921 with new or known good ones. In cases where BGA technologies are used, defects are usually localized by heating.
Before changing the ENG37F03KF tuner, if it is not possible to tune to television channels, you should make sure that there are supply voltages, which must be measured at the corresponding tuner terminals and check the software for correctness. The pulses of data exchange between the tuner and the processor can be monitored with an oscilloscope
Once again, we remind TV users: do not try to repair yourself without the appropriate knowledge, experience and the necessary qualifications! Trust the repair to professionals with sufficient experience in the field of electronic repair.
DOWNLOAD SCHEMATIC DIAGRAM / SERVICE MANUAL ------------------> PANASONIC TX-LR42U20 Chassis KM09
MainBoard TNP4G468 is shown in the figure below:TNP4G468
External view of the power supply
The main features of the PANASONIC TX-LR42U20 device:
Installed matrix (LCD panel) LC420WUN (SC) (D1).
Matrix control uses the LC420WUN-SCD1 Timing Controller (T-CON).
The inverter 6632L-0620A is used to power the backlight lamps.
The formation of the necessary supply voltages for all nodes of the PANASONIC TX-LR42U20 TV is carried out by the TNP4G478 power module, or its analogues using the FA5501AN (C0DBBZG00004), SSC9512 (C0DABYY00025), STR-A6059 (C0DABYY00018) and KEGA0000 B1D60RE type power switches B1CERQ000060).
MainBoard - the main board (motherboard) is a TNP4G468 module, using Nand Flash chips: H27U1G8F2BTR, EEPROM: 24C32, Audio: LV4921 and others.
The ENG37F03KF tuner provides reception of television programs and tuning to channels.
Additional technical information about the panel:
Brand: LG Display
Model: LC420WUN-SCD1
Type: a-Si TFT-LCD, Panel
Diagonal size: 42 inch
Resolution: 1920x1080, FHD
Display Mode: S-IPS, Normally Black, Transmissive
Active Area: 930.24x523.26 mm
Surface: Antiglare (Haze 10%), Hard coating (3H)
Brightness: 500 cd / m²
Contrast Ratio: 1400: 1
Display Colors: 1.06B (8-bit + Dithering), CIE1931 72%
Response Time: 7 (G to G)
Frequency: 60Hz
Lamp Type: EEFL Embedded (Inverter)
Signal Interface: LVDS (2 ch, 10-bit), 51 pins
Voltage: 12.0V