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Old 04-10-2018, 11:24 AM   #1
ageman
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Default Panasonic TX-L42E3B flashing red LED

Hi All

looking for some help. I am having issues with my TV. It will work ok for a few days after the normal panasonic reset.

When the set is in standby with red led, I press the power button on the remote control and all that happens is the led continually flashes red, while the power button is pressed.

I have checked voltages on P2 connector and P4 connector, and all look to be good.

power board is TZRNP01NYUB
A Board is TNP8EA114

any help would be greatly appreciated
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Old 04-10-2018, 01:53 PM   #2
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Default Re: Panasonic TX-L42E3B flashing red LED

Do you have any photo's of your circuit boards. Nice and sharp. Also any voltage readings taken when refusing to come back on?
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Old 04-11-2018, 11:40 AM   #3
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Default Re: Panasonic TX-L42E3B flashing red LED

Here are pictures of the top of boards. Will get voltages when at fault, but ok at the moment. Think maybe main board issue.
Cheers
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Attached Images
File Type: jpg 15234681423703987400074682479296.jpg (635.3 KB, 20 views)
File Type: jpg 15234681671793882138455006879557.jpg (892.5 KB, 14 views)
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Old 04-12-2018, 03:59 AM   #4
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Default Re: Panasonic TX-L42E3B flashing red LED

It could also be worthwhile checking the solder joints on the underside of the power supply board and redoing any that don't look so good.
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Old 04-12-2018, 04:52 AM   #5
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Default Re: Panasonic TX-L42E3B flashing red LED

Hi already did the solder joints
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Old 04-13-2018, 05:46 AM   #6
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Default Re: Panasonic TX-L42E3B flashing red LED

Hi

There has been an issue with panasonic sets of that age and series thats due to data being broadcast. TX**C4,E3, D28 and a few other models seem to be effected

Set will fire up if you switch off mains and then hold in power button as you switch mains back on

Force update software to latest software, turn off new service message and new software message and don't leave in standby
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Old 04-14-2018, 04:43 PM   #7
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Default Re: Panasonic TX-L42E3B flashing red LED

Interesting information.
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Old 04-17-2018, 05:06 AM   #8
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Default Re: Panasonic TX-L42E3B flashing red LED

Hi Davph

I have forced firmware update, has the latest already installed. I left tv turned off not on standby, but getting this issue when turning on by main power button. Have not had chance to check voltages yet.
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Old 04-24-2018, 09:17 AM   #9
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Default Re: Panasonic TX-L42E3B flashing red LED

Hi Guys
I have taken voltages for the two plugs P4 and P2 please see attached.

Any help on where to look next would be appreciated. I don't think it's anything to do with leaving in standby or firmware, as the TV has had no problems since I bought it from new.

Cheers
Adrian
Attached Files
File Type: xlsx P2 and P4 voltages.xlsx (12.4 KB, 6 views)
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Old 04-24-2018, 09:35 AM   #10
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Default Re: Panasonic TX-L42E3B flashing red LED

Can you check this schematic matches your power supply.

The backlight (BL_ON) is being switched off and a backlight error (BL_SOS) is being generated.
Attached Images
File Type: jpg PSU Volts.JPG (107.8 KB, 14 views)
Attached Files
File Type: pdf tnpa5364.pdf (730.7 KB, 13 views)
File Type: xlsx P2 and P4 voltages.xlsx (12.2 KB, 7 views)

Last edited by dick_barton; 04-24-2018 at 10:09 AM..
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Old 04-24-2018, 10:15 AM   #11
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Default Re: Panasonic TX-L42E3B flashing red LED

Hi

yes that is the correct schematic. Do you want me to check the backlights are off?
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Old 04-24-2018, 10:18 AM   #12
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Default Re: Panasonic TX-L42E3B flashing red LED

Found a picture of the complete sets circuit boards after searching this site.
You either have bad leds or possible led driver board.
Can you post a picture of the blue circuit board with metal shield removed so that any text on the board can be read.
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File Type: jpg bad2.jpg (2.89 MB, 12 views)
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Old 04-24-2018, 10:54 AM   #13
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Default Re: Panasonic TX-L42E3B flashing red LED

Here is the led board
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File Type: jpg 20180424_172536_resized.jpg (1.17 MB, 23 views)
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Old 04-24-2018, 11:32 AM   #14
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Default Re: Panasonic TX-L42E3B flashing red LED

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Old 04-25-2018, 10:23 AM   #15
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Default Re: Panasonic TX-L42E3B flashing red LED

Thanks dick barton and thoma. I have taken the tv apart and checked all the diodes, some are a bit iffy. I have managed to get some from a tv with broken screen awaiting arrival. Have also checked the LED board, andit looks like D100 has failed short circuit. It is marked UF 36. Assume it is a 36 volt diode, but not sure as cannot find a schematic for this PCB
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Old 04-25-2018, 11:17 AM   #16
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Default Re: Panasonic TX-L42E3B flashing red LED

You need to be careful when replacing diodes. Some are Ultrafast rectifying diodes and need to be replaced with likewise and not general purpose diodes.
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Old 04-25-2018, 11:37 AM   #17
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Default Re: Panasonic TX-L42E3B flashing red LED

I've ordered a replacement board to be on the safe side. I assume UF means Ultra Fast, but wasn't sure
Cheers
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Old 04-25-2018, 12:00 PM   #18
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Default Re: Panasonic TX-L42E3B flashing red LED

Out of interest what components numbers on the power supply did you consider were faulty.
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Old 04-25-2018, 01:57 PM   #19
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Default Re: Panasonic TX-L42E3B flashing red LED

Sorry meant to say led's were iffy not diodes. Only had a quick check on the led driver board and found diode no 100 was short circuit. Got another led driver board for 11 fully tested. So not going to check out any further
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Old 04-25-2018, 10:47 PM   #20
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Default Re: Panasonic TX-L42E3B flashing red LED

https://www.badcaps.net/forum/attach...2&d=1524588829
Quote:
Originally Posted by ageman View Post
Sorry meant to say led's were iffy not diodes. Only had a quick check on the led driver board and found diode no 100 was short circuit. Got another led driver board for 11 fully tested. So not going to check out any further
D100 is connected in series with LOW OHM R143, that R/D NETWORK is then connected in parallel with R100 (about 10 Ohms) so that is why the diode shows conduction in both directions; that whole R-D/R network is for the Gate discharge circuit for that MOSFET Q100. It has the exact same setup at the Gate of Q200 (R243, R200, D200) for the #2 Booster circuit.
Q100 is one of the two Voltage booster circuits, Q200 is second booster circuit.

So the question is what Voltages do you have on all the pin of that white connector CN1 on that LED power supply/driver board when TV is OFF and when power switch is activated?
What Voltage do you have when measure between the two legs of C1 (680uF 35VDC) when TV is off and when power switch is activated?
What Voltage do you have when measure between the two legs of C104 and C204 when TV is OFF and when power switch is activated?
BTW, you have 10 strings of LEDs: VL1 ~ VL5, VR1 ~VR5.
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