Panasonic TH-L50B6D LED 1 Blink Code

[BookWormStud]

Hello,

Posted a problem on reddit & badcaps (O/G post) about Panasonic Viera TH-L50B6D.

TL;DR Backlights turning ON and OFF. LED screen is alright did the flash light test. After sometime TV goes to standby with Red Light Blinking. Reduced brightness, now TV stays ON but backlight turning ON & OFF.

[UPDATE] Someone on reddit provided me with the Service Manual (don't download I'll provide important images later) of TV almost similar to that of my TV. Only difference is Main/A-Board (that too in position of connections everything else is same).

Take a look at these:

Overall Schematic

Wiring Diagram

Block Diagram 1 A-Board

Block Diagram 2 Other Boards


Now I'm asking, Is there any way to jump the wires with A/Main-Board disconnected from P/Power Board and turn ON the backlights.

I read a post by downunder [Truly A HERO Member]Post

downunder
when I asked about the post he said he meant like this.
I don't know if same applies in my because someone on reddit suggested me to do it like this can anyone confirm


Thanks. Any other Info you need please comment.

[downunder]

Your original symptoms were error code 1 - this is a backlight SOS.

Reduced brightness, now TV stays on but backlights flicker. That means POWER-ON signal is being supplied to the power supply from the A-board.

Check it - should be anywhere from 2V to 5V, DC and steady.

So there should be no need to link Power-On to the 5V Standby rail.

Merely link BL-ON pin to the 5V pin. Backlights OK, then A-board most likely faulty, but also check screen for any darker areas

which means some of the backlight LEDs are out.                                      Bruce

[BookWormStud]

I tried what you said nothing happens.
I also tried with POWER_ON pin connected still nothing. Check if this is correct

[downunder]

OK, it looks like we're working on different variants of the P-board. The TH-P50B6A uses 13 pins on P2. The TH-P50B6Z uses 14 pins. Your block diagram 2/2 shows 13 pins. Your Overall diagram and your last post show 12 pins. Obviously the connections will all be different.

Your picture of the P-board shows no markings at the plug to say which pin does what. Have you checked the underside of the P-board to see if the pins are titled there?
If not, place the TV in standby and measure the pins on P2 for voltage. Only 1 pin will have volts, that's the Standby pin which will read about 5.3V. From there you'll have to work out Power-on pin and BL-ON pin. I'm starting to get as confused as you now.       Bruce

[BookWormStud]

OK, it looks like we're working on different variants of the P-board. The TH-P50B6A uses 13 pins on P2. The TH-P50B6Z uses 14 pins. Your block diagram 2/2 shows 13 pins. Your Overall diagram and your last post show 12 pins. Obviously the connections will all be different.

Your picture of the P-board shows no markings at the plug to say which pin does what. Have you checked the underside of the P-board to see if the pins are titled there?
If not, place the TV in standby and measure the pins on P2 for voltage. Only 1 pin will have volts, that's the Standby pin which will read about 5.3V. From there you'll have to work out Power-on pin and BL-ON pin. I'm starting to get as confused as you now.       Bruce

I checked the Part No. of P-Boards on 2 Service Manual [TX-L50B6B & TX-L50B6E] they both have same No. TXN/P1ZPUE [TNPA5807 2P] as mine & they too show the same block diagram with 13 Pins as I have provided above but have 14 pins in reality. (Check Images)


Is there anyway to check which pins are BL_ON & POWER_ON by checking the voltages.

Why do we need a resistor? Can't we simply jump with a piece of wire?
I read a post on justanswer.com where they suggested to jump wires directly with single piece of wire, no resistor.

[downunder]

Best to use a resistor. It protects the circuits connected to the pins from inrush current as these pins never go above 3.5V during normal
operation. Never know what ICs or switching transistors are in line.

About identifying the pins....a bit haphazard and tricky. You can eliminate maybe 3 ground pins which should read near zero ohms to the chassis ground, eg the tuner case. I explained how to identify the Standby 5V pin. A couple of pins

Power-On and BL-On will read near zero volts in standby, and rise rapidly towards 3.5V when power is activated. However other pins, eg PWM may also imitate this and rise as well. A bit hairy, I'd say.

BTW: Do you have 24V at LD1, and what voltages do you get at the pins on LD3?

[BookWormStud]

Best to use a resistor. It protects the circuits connected to the pins from inrush current as these pins never go above 3.5V during normal
operation. Never know what ICs or switching transistors are in line.

About identifying the pins....a bit haphazard and tricky. You can eliminate maybe 3 ground pins which should read near zero ohms to the chassis ground, eg the tuner case. I explained how to identify the Standby 5V pin. A couple of pins

Power-On and BL-On will read near zero volts in standby, and rise rapidly towards 3.5V when power is activated. However other pins, eg PWM may also imitate this and rise as well. A bit hairy, I'd say.

BTW: Do you have 24V at LD1, and what voltages do you get at the pins on LD3?

I checked all the voltages you can check here

Also attaching the Circuit Diagrams of Connectors of P & LD-Boards from service manual of TX-L50B6B because I checked the Model No. & Part No. which matches with that of my TV.

Hope you can make something out of it.

[downunder]

At a guess, P-AO9, pin 6 = Standby 5V (stable), pin 9 = Power-On (stable), pin11 = BL-ON (all over the place).

                 P4, pin 3 = BL-ON (all over the place).

                 LD3, pins 3 and 9, LED supply volts, should be stable.

Suggestion: cut the lead going to pin 11 of P-AO9 in a place where it can be resoldered later on. Make sure all plugs are in place. Then place your resistor between pins 6 and 11 of P- AO9. Now you are controlling the backlights, not the A-board. If pin 11 is now stable, then the A-board is causing your previous fluctuations. If the backlight don't light up, I'd say you have dead LED/LEDs in the display panel - LG panel, is it? Quite common.

Don't suppose you have a LED tester? My guess is based on the voltages you have supplied and may not be accurate. Good work on your attachments.

Bruce

[BookWormStud]

At a guess, P-AO9, pin 6 = Standby 5V (stable), pin 9 = Power-On (stable), pin11 = BL-ON (all over the place).

                 P4, pin 3 = BL-ON (all over the place).

                 LD3, pins 3 and 9, LED supply volts, should be stable.

Suggestion: cut the lead going to pin 11 of P-AO9 in a place where it can be resoldered later on. Make sure all plugs are in place. Then place your resistor between pins 6 and 11 of P- AO9. Now you are controlling the backlights, not the A-board. If pin 11 is now stable, then the A-board is causing your previous fluctuations. If the backlight don't light up, I'd say you have dead LED/LEDs in the display panel - LG panel, is it? Quite common.

Don't suppose you have a LED tester? My guess is based on the voltages you have supplied and may not be accurate. Good work on your attachments.

Bruce

First of all Thanks for even reading that.

Secondly, P-A09 Connector (Stand By) I wrote Pin 3 = 133V instead of 0.133V Sorry for that.

No I don't have a LED Tester. Sorry.

You said Pin 3 = BL_ON at P4 and Pin 11 = BL_ON at P2, But the diagram says Pin 2 & Pin 12 Respectively. Please Explain.

About LD3 Pin 3 & Pin 9, voltages fluctuate cause Backlights are turning ON & OFF.
Yes It has the LG Panel the infamous LC500DUE (SF)(R1)


Also, if I cut the Pin 11 wire attach it to a resistor how am I be able to connect to Pin 6 with the connector plugged in. Or should I do it like this

[downunder]

The BL-ON function of pin on P2 (14 pin) I have surmised from the behaviour of the voltages you provided. You say it fluctuates between 1V and 4.5V. I could be wrong, but 4.5V this sounds like the level BL-ON would reach. The functions you have allocated to P2 on your attachment (last post) - are they the real deal as per service manual for your model? This keeps confusing me, the different number of pins in various attachments.

Re the resistor, my intention was for you to do it with all connectors in place. You can either force it into the top of P2 or solder it to the relevant pins on the underside of P2. THen, A-Board supplies Power-On, you supply BL-ON.

Bruce

[BookWormStud]

The BL-ON function of pin on P2 (14 pin) I have surmised from the behaviour of the voltages you provided. You say it fluctuates between 1V and 4.5V. I could be wrong, but 4.5V this sounds like the level BL-ON would reach. The functions you have allocated to P2 on your attachment (last post) - are they the real deal as per service manual for your model? This keeps confusing me, the different number of pins in various attachments.

Re the resistor, my intention was for you to do it with all connectors in place. You can either force it into the top of P2 or solder it to the relevant pins on the underside of P2. THen, A-Board supplies Power-On, you supply BL-ON.

Bruce

OK I tried some new things,
Firstly I discovered that Pin 12 on P2 Connector is indeed BL_ON.
Now what I did, With every connector attached I one by one disconnected the wires labeled
BL on Connector connected to A09. Pin 12 when disconnected Backlights don't light up.
Then Connected Pin 12(removed from connector A09)
to Pin6 of 5Vs (connected at Connector A09)
Like this
Backlights light up but same flickering. Also disconnected every other wire with BL prefix
Thought maybe they were sending a bad signal but no luck.


I wanted to ask another question. If one or more of the LED in backlights is bad then when directly
Connected to 5Vs shouldn't it give maybe dim light but constant why do they flicker if LEd is short or bad?

[downunder]

Wrt your procedure, I would expect the backlights to be constant. At least that eliminates the A-board, but you have a problem elsewhere. Could be the LD-board but they're generally reliable. Most likely a faulty LED. Also, when you remove other BL related cables, you're removing other info related to BL operation e.g. PWM (pulse width modulation) controls the brightness and current of the LEDs, BL-Error tells the micro of any defects in the LEDs which generates Code 1.

Ever pulled a panel apart to expose the back light LEDs? Might be a big ask for a dabbler as you could end up with a cracked display panel.

Bruce

[BookWormStud]

Wrt your procedure, I would expect the backlights to be constant. At least that eliminates the A-board, but you have a problem elsewhere. Could be the LD-board but they're generally reliable. Most likely a faulty LED. Also, when you remove other BL related cables, you're removing other info related to BL operation e.g. PWM (pulse width modulation) controls the brightness and current of the LEDs, BL-Error tells the micro of any defects in the LEDs which generates Code 1.

Ever pulled a panel apart to expose the back light LEDs? Might be a big ask for a dabbler as you could end up with a cracked display panel.

Bruce

Haven't even opened a back cover of an LED TV before. I'm thinking of replacing Backlight as Last Resort. I just wanted to turn on the Backlights with A-Board disconnected which is the main issue, if I somehow be able to rule A-Board out to be good then I'll move on.
But it seems like impossible.

I think Now what I'm gonna do I'm gonna use a resistor to jump Pin 6 = 5V to all other pins which gives a Backward & Forward signal all together.

Is there any other way to put DC voltage (using a battery) to LD3 and turn a strip ON. Is it even possible?

Another question how can I check Backlight array model?

[BookWormStud]

One more thing I read a post on justanswer.com TL;DR Some resistor were open circuit that's why Backlights flicker.

I check the resistors on my P-Board there are total of 3 resistors which read open circuit. Every other resistor makes a beep sound on my Multimeter under continuity test (which states that circuit is complete). Is this natural or something is wrong?

Open Resistors on P-Board
Top View
Bottom View

EDIT :
Turns out those resistors values were more than the range of my Multimeter's Continuity test.That's why they didn't beep. So ignore this.

[downunder]

You've already ruled out the A-board by severing the BL-ON lead and activating the LEDs using the resistor bridge.

Resistors shown appear to be 1 megohm so they wont beep.

I cannot recommend linking pin 6 willy-nilly to other pins on the plug. You don't know what damage you'll do, especially to the 1.8V rail.

Power-On and BL-ON are the only two we ever bridge out to the 5V pin.

Re applying voltage to the LED strips, that is where we use the LED-Strip Tester. It automatically and gently ramps up the volts it applies to a strip until

the strip illuminates and then it stops there. If you open the panel, you can test individual LEDs with your digital meter on diode mode. Some meters 

will apply enough volts to light up a single LED provided it's connected in the correct lead polarity. One way works, other way not.