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Manufacturer: Panasonic

Type: TX-L42ETW5

Chassi: LA35



Hello everybody,

I could determine or measure the following with the device:

Device does not start anymore, stand-by LED lights red when device is plugged in and flashes red as soon as an IR command (key press) is sent via the remote control. Voltages of power supply STB 5V and signal LCD_TV_SUB_ON come from A-board. Power supply starts, supplies P15V and SUB1.1V, 1.5V, 1.8V, 3.3V, 5V, HDMI3.3V and USB5V are generated on the A-Board (stand for about 2.5 seconds). Then signal LCD_TV_SUB_ON goes low (voltages go away to STB 5V) and after about 2 seconds back to high (endless). What is missing is the voltage PNL12V which is switched on by PANEL_VCC_ON2. PANEL_VCC_ON2 always has a low signal and does not change its state. Power supply also provides for the 2.5 seconds the 24V for the backlight. Clocking of LCD_TV_SUB_ON starts immediately after plugging in the mains plug (also without IR command). SOS error code is not output. The over-voltage circuit in IC 5000 pin 7 also does not respond. Attached is the timing diagram from the technical training of Panasonic where I have drawn until when the boot process behaves normally.

In my opinion a mistake on the A-board? Does anyone have a tip?

greetings

Andi

My old TV has just broke a day ago, and when i try turning it on, relay is clicking and tv is not starting. I have heard that it probably has magnificying transformer broken.

:taps2: This is a LCD TV brand EMERSON, model LC320EM3F and is completely death. At first revision, we detected some bad components in the switching power source: Switching MOSFET K10A50D, RESISTOR 0.19 Ohm, 2W, transistor switching controler 2SC5344, Zener Diode 1ZB36 (36V) and the 4A fuse. I had the SM of LC320EM9 model, so, the values of the components are different. I replace them all twice and they always broke again! FRUSTRATING! Then I realyze that changin the values nearly to the LC320EM9 model, I would obtain better results (see FILE ATTACHED) I replace the 0.19Ohm resistor by a 0.39Ohm, maximizing the pulse received for the control transistor, for that purpose, also changed the 2.4KOhm resistor for 5.6KOhm. The switching MOSFET used was IRF640 replacing K10A50D, and transistor 2SC5344 was replaced by 2N5551. Finally we add a Zener diode not included in original board (marked with blue circle) limiting the colector voltage and gate voltage to 26V. For short, when we connect the power cord, every thing was fine, except than voltages at secondary of main transformer, was only 3.2V DC in all rectifiers. Found a diode in short-circuit (circled in red), replaced it and BINGO!, the TV return to live again!!!! I Hope it serves as a nice experience for the future.