REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

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Wednesday 2 September 2020

REPAIRING / SERVICING TV PANASONIC TX-20LA70

Technical description and composition of the PANASONIC TX-20LA70 TV, panel type and modules used. The composition of the modules.
PANASONIC
Model: TX-20LA70
Chassis / Version: GLP21L
Panel: V201V1-T03 L5EDD5L00011 640x480 VGA 4: 3
Lamp backlight: 6 Lamp CCFL
Inverter (backlight): integrated into PSU
PWM Inverter: STR-H2003
MOSFET Inverter: TPC8022-H
Power Supply (PSU): TNP0EP008
PWM Power: MR4030-7102
MainBoard: TNP0EA008 8 A
IC MainBoard: CPU: VCT6753G-FA, EEPROM: 24C32
Tuner: ENGF7701GF
Control: Remote: EUR765101B
TX-20LA70 Specifications
PANASONIC TX-20LA70
General recommendations for TV LCD repair
Possible manifestations of defects
- PANASONIC TX-20LA70 TV does not turn on. There are no signs of operability. The indicators on the front panel do not light or blink, the TV does not respond to the remote control and control buttons.
With such manifestations, the TNP0EP008 power supply module usually fails. It is necessary to measure its output voltages, and if they are absent (full or partial), the serviceability of the power switches of the converters and rectifier diodes should be checked for a possible short circuit.
In case of any breakdown of semiconductors in the secondary circuits, the converter can usually operate normally in an emergency short-circuit mode. There are no output voltages. And with a short circuit in the power elements of the primary circuit, as a rule, the mains fuse breaks and, less often, the current sensor in the source of the key.
The breakdown of power switches (MosFet) in switching sources is sometimes caused by malfunctions of other circuit elements, for example, in the circuits supplying the PWM controller, frequency setting or damper, as well as in the circuits of Negative Feedback (OOS) stabilization. PWM regulators (PWM) MR4030-7102, if they have no visible damage to the case and an outright short circuit between the terminals, are usually checked by replacement.
- There is no picture, but there is sound and reaction to commands from the remote control. Or the image appears immediately after switching on and disappears.
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 keys of the converter and the secondary windings of the transformers.
If, when diagnosing a malfunction, it is required to turn off the inverter protection, there is a risk of failure of the power elements of the inverter, and special care is required during work, and after they are completed, it is imperative to restore the protection circuits for further safe operation of the TV by the owner in normal mode.
- The TV does not go into operation, does not respond to the remote control. The indicator on the front panel is on or blinking.
Repair or diagnostics of the TNP0EA008 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). Sometimes it is necessary to check or replace (if necessary) the elements of the MainBoard - CPU: VCT6753G-FA, EEPROM: 24C32. In cases where a BGA processor is used, its malfunction is usually detected by the local warm-up method.
If you suspect a malfunction of the ENGF7701GF tuner, first of all, you need to make sure that the software is correct, as well as the presence of the necessary levels of supply voltages and pulses of data exchange with the processor via the I2C bus on the corresponding terminals of the tuner.
Attention to TV owners! Attempts to repair PANASONIC TX-20LA70 on your own are not recommended by the manufacturer and can lead to serious negative consequences!
DOWNLOAD SCHEMATIC DIAGRAM  / SERVICE MANUAL   ------------------>    PANASONIC TX-20LA70 Chassis GLP21L    for models  20LA70F, TX-20LA70P, TX-20LA7F, TX-20LA7P


 The appearance of the MainBoard TNP0EA008 is shown in the figure below:
TNP0EA008
External view of the power supply
The main features of the PANASONIC TX-20LA70 device:
Installed matrix (LCD panel) V201V1-T03 L5EDD5L00011 640x480 VGA 4: 3.
To power the backlight lamps, a converter combined with a power supply is used, controlled by the STR-H2003 PWM controller. TPC8022-H keys are used as power elements of the inverter.
The formation of the necessary supply voltages for all nodes of the PANASONIC TX-20LA70 TV is carried out by the TNP0EP008 power module, or its analogs using MR4030-7102 microcircuits.
MainBoard - the main board (motherboard) is a TNP0EA008 module, using CPU chips: VCT6753G-FA, EEPROM: 24C32 and others.
The ENGF7701GF tuner provides reception of television programs and tuning to channels.
Additional technical information about the panel:
Brand: CMO
Model: V201V1-T03
Type: a-Si TFT-LCD, Panel
Diagonal size: 20.1 inch
Resolution: 640x480, VGA
Display Mode: TN, Normally White, Transmissive
Active Area: 408x306 mm
Surface: Antiglare
Brightness: 500 cd / m²
Contrast Ratio: 600: 1
Display Colors: 262K (6-bit), CIE1931 75%
Response Time: 3/5 (Tr / Td)
Frequency: 60Hz
Lamp Type: 6 pcs CCFL Without Driver
Signal Interface: TTL (1 ch, 6-bit), 50 pins
Voltage: 5.0V (VCC)
PANASONIC TX-20LA70 TV with LCD V201V1-T03, size 20 "diagonal 4: 3. The brightness of the screen is 450 cd / m2 provided by CCFL (EEFL) fluorescent lamps. Contrast, as the ratio of maximum brightness to minimum, is 500 : 1. Input analog video signal can be processed in PAL, SECAM, NTSC systems Graphic processing and image formation of digital signal occurs in 480i, 480p, 576i standards.
The power of the acoustic audio system is 6 W (2x3 W), provided by two speakers. NICAM STEREO sound processing system is used.
The external interface (communication with other devices) is supported by standard input and output connectors: antenna input (RF), AV, S-Video, SCART, RGB. A headphone output is provided for individual listening.
The power consumed by the TV in operating mode from the network is 65 W.
Dimensions: with stand 498x484x260 mm, without stand 498x443x98 mm.
TV weight: with stand: 9.3 kg, without stand: 7.5 kg.
Attention! The V201V1-T03 panel of the PANASONIC TX-20LA70 LCD TV is a rather expensive component.
Avoid impacts on glass and pressure on the surface of the screen to avoid irreversible damage to the LCD panel!
Posted By: FRANK at 05:22
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