Panasonic TH-L50B6D LED 1 Blink Code

[BookWormStud]

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.

OK about checking the voltage with an external battery, I meant that if we can check the LED Backlight without even opening the panel. Can a LED tester check the backlights without opening the panel, If it can I would buy one.


I came to the conclusion that when jumping Pin6 STB5V & Pin 12 BL_ON the backlights didn't turn ON because all the other voltages to connectors P4 & LD1 were missing. Also when I jumped the above said pins the voltages were equal to 5VS.

Now if you would check my voltage sheet specifically on P2 (Turned ON) Pin 12 = BL_ON it gives 0.51V while every where else it's 2.37V

Question: Is there any way to check what voltages should a capacitor give?

[downunder]

So, a LED Tester can test the backlights without stripping the panel. 34USD with free delivery should get you one from here:

https://www.aliexpress.com/popular/led-tester-lcd-tv-led.html

Like a voltmeter, + and - probes, applied between LED1 and Anode1 then LED2 and Anode 2 on connector LD3. Depending on the layout of the LEDs,

each application should light up one half of the LEDs, then the other half.


Your connector configurations are confusing me. You give the voltage table for A09. Do the leads in the loom mirror each other at the plugs or do some

wires in the loom cross over to different pins. Does this table show the actual pins in your TV and are you counting the pins from the correct end of the

plug. Usually pin 1 is identified in some way by an arrow head screen-printed on the board near pin 1 of the socket.

Going by your table, pins 2 (up to 3.41), and 4 (0.99 to 4.5 fluctuating) are the only pins behaving like a BL-ON signal, yet you say pin 12 = BL-ON.

Re capacitors, they don't actually give voltage, but they can store a voltage. Their upper voltage rating is stamped on the casing. This is the max

voltage that can healthily be applied to the capacitor. Any voltage over this will cause heat stress in the capacitor until it ruptures the top or bottom

casing.               Bruce

[jordan]

http://www.tv.quuq.org/forum/index.php?topic=10225.msg29799#msg29799

[BookWormStud]

So, a LED Tester can test the backlights without stripping the panel. 34USD with free delivery should get you one from here:

https://www.aliexpress.com/popular/led-tester-lcd-tv-led.html

Like a voltmeter, + and - probes, applied between LED1 and Anode1 then LED2 and Anode 2 on connector LD3. Depending on the layout of the LEDs,

each application should light up one half of the LEDs, then the other half.


Your connector configurations are confusing me. You give the voltage table for A09. Do the leads in the loom mirror each other at the plugs or do some

wires in the loom cross over to different pins. Does this table show the actual pins in your TV and are you counting the pins from the correct end of the

plug. Usually pin 1 is identified in some way by an arrow head screen-printed on the board near pin 1 of the socket.

Going by your table, pins 2 (up to 3.41), and 4 (0.99 to 4.5 fluctuating) are the only pins behaving like a BL-ON signal, yet you say pin 12 = BL-ON.

Re capacitors, they don't actually give voltage, but they can store a voltage. Their upper voltage rating is stamped on the casing. This is the max

voltage that can healthily be applied to the capacitor. Any voltage over this will cause heat stress in the capacitor until it ruptures the top or bottom

casing.               Bruce

1. About LED tester if I order it from Aliexpress, I'll get it by atleast 45 Days. And If order it from online stores in my country its gonna cost like $200. I'll surely check the local stores and try to find a cheaper one.

2. I'm sorry for confusing you about the 0.51V (Stable) on Pin 12 P2 Connector in my last post. I checked that again it came to be 2.37V (Stable).


Also I'm so sorry if my explanation was confusing for you. A09 connections are like this, you can see that wires 3 & 4 are missing and also P2 pins are inverted(A09 labels top to bottom while P2 does from bottom to top).

Not everything is labelled but Connector names (eg. P2, P4, A09 etc.) and Starting & Ending Pins are Labelled (eg. on P2 1&14, on A09 1&12 etc.) You can check the labelling here.

That's why Pin 12 (on P2 connector) = BL_ON and Pin 3 (on A09 connector) = BL_ON is stable at 2.37V.

Also Pin 11 (on P2 connector) = BL_SOS and Pin 4 (on A09 connector) = BL_SOS which are fluctuating between 1 & 4.5V.

3. Question : I know that BL_ON voltages are for turning Backlights ON & BL_PWM is to control it's brightness But what I wanted to know was that what is the function of BL_SOS?


4. Also since every other voltage is almost stable except for BL_SOS (Pin11, Pin 3 & Pin 3 on connectors P2, P4 & LD1 respectively) which is fluctuating between 1 to 4.5V, I thought maybe a Bad LED in the backlight is triggering it to fluctuate.

So I disconnected the LD3 connector (i.e. disconnected Backlight from the LD-Board) but the BL_SOS was still fluctuating at every Pin mentioned above (1V-4.5V).

Then I disconnected the LD1 connector (i.e. disconnected LD-Board from the P-Board ) now all the BL_SOS voltages came to 3.18V(Stable).

Is this info any helpful to diagnose any further?

[downunder]

Hi, starting to make more sense, now. So SOS (danger) signal. Various sections of the TV are monitored for abnormal activity or operation. In such a case

an error signal is fed to the microprocessor on the A-board which usually reacts by shutting the set down and issuing a relevant error code by flashing the

standby light in a certain sequence. So BL-SOS tells the micro that there's a problem in the backlight circuits.

Theoretically, unplugging LD3, then LD1, would mean the problem is with the LD-board, but with LEDs disconnected, the micro can still sense

something's still not right.


Did you see Jordan's post re backlight damage in this model. I would expect BL-SOS to be near zero volts in a normally operating TV. Why not see what

happens if you run any BL-SOS pin to earth via a shorting link. Also, have you seen this bulletin. 45 days ex China is a bit ridiculous - I see, free

delivery. Must be sending by sea mail. We usually get stuff within 14 days by economy air mail.       Bruce

[BookWormStud]

Hi, starting to make more sense, now. So SOS (danger) signal. Various sections of the TV are monitored for abnormal activity or operation. In such a case

an error signal is fed to the microprocessor on the A-board which usually reacts by shutting the set down and issuing a relevant error code by flashing the

standby light in a certain sequence. So BL-SOS tells the micro that there's a problem in the backlight circuits.

Theoretically, unplugging LD3, then LD1, would mean the problem is with the LD-board, but with LEDs disconnected, the micro can still sense

something's still not right.


Did you see Jordan's post re backlight damage in this model. I would expect BL-SOS to be near zero volts in a normally operating TV. Why not see what

happens if you run any BL-SOS pin to earth via a shorting link. Also, have you seen this bulletin. 45 days ex China is a bit ridiculous - I see, free

delivery. Must be sending by sea mail. We usually get stuff within 14 days by economy air mail.       Bruce

1. OK Please elaborate this "Why not see what happens if you run any BL-SOS pin to earth via a shorting link.", How do I ground BL_SOS? (I'm a Noob :p)

2. Secondly about LED tester if I choose the DHL Shipping its costs like $25 more (6-13 Days). But that's not it, Custom Import charges are like 30-50 % of the price of product.

3. I checked those SMD FET Transistors. I checked them in circuit with my DMM at continuity test. Sometimes there's brief(like 1/2 second) beep sound when Drain & Source are probed, after that it shows a reading of 436. Otherwise they seem fine. I'm not that good at soldering but I'll ask someone to replace them with new ones.

4. Also I found this. His problem was same like mine But in his case voltages are different than mine.

 

[downunder]

OK, see what you mean about the LED Tester. Perhaps Turnip will enlighten you about where he sourced his tester from - I don't think he paid anything like that for his.

Forget about the FETs -they measure OK. Re the Badcaps post, I don't find anything useful there.

The BL-SOS pin should, I expect, measure virtually 0V in a normally operating TV. So, to simulate the 0V status, you would use a piece of wire and connect it between the the BL-SOS pin and the main metal chassis, or use some sharp tweezers to connect between the BL-SOS
pin and any earth (=ground) pin on the exposed top of P2. Just interested if this stabilises the backlights.             Bruce

[BookWormStud]

Like this

[kennyc]

Hello . When I am checking the LED strips I just use 2 transformers  from the Xmas tree lights . You know the one that plugs into the wall and lights them . One has 12V output and the other 24V . If you are testing 8 LEDs use the 24V supply and if its 2 sets of 4 with a joinig cable betweeen them use the 12V one. I know its a bit basic but if its just to see if they all light or some are duff its a simple and easy way to do it

[rshankarvi]

I think you should use this link where you will get best solution with step by step.
http://lcdrepair.co.in/
 

[BookWormStud]

Hello . When I am checking the LED strips I just use 2 transformers  from the Xmas tree lights . You know the one that plugs into the wall and lights them . One has 12V output and the other 24V . If you are testing 8 LEDs use the 24V supply and if its 2 sets of 4 with a joinig cable betweeen them use the 12V one. I know its a bit basic but if its just to see if they all light or some are duff its a simple and easy way to do it

Do you have some pictures of the circuit?

[downunder]

Re post # 22, yes, that's what I meant by earthing BL-SOS pin. If you can find the specs for your panel model, it'll probably reveal number of LEDs, how they're wired and maybe voltages required to operate them.

Bruce

[kennyc]

Hello again . Only use these transformers to check the LED strips once I have opened the panel up and can test each strip individually

[BookWormStud]

OK, see what you mean about the LED Tester. Perhaps Turnip will enlighten you about where he sourced his tester from - I don't think he paid anything like that for his.

Forget about the FETs -they measure OK. Re the Badcaps post, I don't find anything useful there.

The BL-SOS pin should, I expect, measure virtually 0V in a normally operating TV. So, to simulate the 0V status, you would use a piece of wire and connect it between the the BL-SOS pin and the main metal chassis, or use some sharp tweezers to connect between the BL-SOS
pin and any earth (=ground) pin on the exposed top of P2. Just interested if this stabilises the backlights.             Bruce

I tried grounding the BL_SOS to Metal Chasis, Nothing. I'm gonna try one more time, reassuring Ground BL_SOS like in attachment image.
with everything connected, right?

Also I found a post for testing Inverter Boards, I couldn't understand it properly. Here.

[Turnip]

Hi, hadn't replied before as my Led Lcd tester seems no longer available.

It's nifty as applied polarity is unimportant - Strings being O/C connected the wrong way around.

Mine works automatically with a single Led or a string up to 200v where checking a screen it displays applied voltage so strings of different lengths are identified.

Trouble is if you don't know how many Leds are in a string, you don't know if one or more is S/C without taking the screen apart but it's good with an O/C string indicating max voltage far above the string usual.

Most inverters cut if a single diode is S/C or O/C after the initial power up to check. so a quick test with a meter gives an idea as to where the problem might be.

Noticed something recent and similar on Ebay from China at £18.00 inc post - Chris.