Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: BookWormStud on August 12, 2017,08:01:29
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Hello,
Posted a problem on reddit & badcaps (O/G post) (https://www.badcaps.net/forum/showthread.php?t=63794) 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 (https://nohm.eu/schematics/Panasonic/TX-L50B6E%20Service%20Manual.pdf) (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 (https://drive.google.com/open?id=0BzpaeXutpVmJRWlXdkl0dmtzWDg)
Wiring Diagram (https://drive.google.com/open?id=0BzpaeXutpVmJRzhzc3hGZG5mVGc)
Block Diagram 1 A-Board (https://drive.google.com/open?id=0BzpaeXutpVmJS3hlUTlLTkVsVzg)
Block Diagram 2 Other Boards (https://drive.google.com/open?id=0BzpaeXutpVmJbVdxMnNpX0ZlVzQ)
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 (http://www.tv.quuq.org/forum/index.php?action=profile;u=18459) [Truly A HERO Member]Post (https://drive.google.com/open?id=0BzpaeXutpVmJbFdJRFowYlkySlk)
downunder (http://www.tv.quuq.org/forum/index.php?action=profile;u=18459)
when I asked about the post he said he meant like this. (https://drive.google.com/open?id=0BzpaeXutpVmJUnJUbWVQVkhfUEk)
I don't know if same applies in my because someone on reddit suggested me to do it like this (https://drive.google.com/file/d/0BzpaeXutpVmJUnRROC1jeVdGdFk/view?usp=sharing) can anyone confirm
Thanks. Any other Info you need please comment.
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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
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I tried what you said nothing happens.
I also tried with POWER_ON pin connected still nothing. Check if this is correct (https://drive.google.com/open?id=0BzpaeXutpVmJdVhrVzJEREVLZE0)
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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
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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.
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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?
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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 (https://drive.google.com/open?id=0BzpaeXutpVmJZklXMGc3TzRSN00)
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.
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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
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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 (https://drive.google.com/open?id=0BzpaeXutpVmJZ3kyRXNLQlRPams)
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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
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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 (https://drive.google.com/open?id=0BzpaeXutpVmJX2dmYS05dlE0RjQ)
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?
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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
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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?
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One more thing I read a post (https://www.justanswer.com/tv-repair/8mphm-42-rca-led-tv-screen-keeps-flickering.html) 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 (https://drive.google.com/open?id=0BzpaeXutpVmJQlVOMmVrY3Rla2M)
Bottom View (https://drive.google.com/open?id=0BzpaeXutpVmJNEZYdlV1b0pWdGc)
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.
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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.
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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 (https://drive.google.com/open?id=0BzpaeXutpVmJZklXMGc3TzRSN00) 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?
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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
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http://www.tv.quuq.org/forum/index.php?topic=10225.msg29799#msg29799
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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 (https://drive.google.com/open?id=0BzpaeXutpVmJZ3kyRXNLQlRPams), 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 (http://i.imgur.com/eqXlRRp.jpg).
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 (https://drive.google.com/open?id=0BzpaeXutpVmJcnBxc3M3eVg3M1E), P4 (https://drive.google.com/open?id=0BzpaeXutpVmJTV84UVlMbmkxRzA) & LD1 (https://drive.google.com/open?id=0BzpaeXutpVmJYldSVmRsOVptbzQ) 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?
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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
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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 (http://www.badcaps.net/forum/showthread.php?t=51587). His problem was same like mine But in his case voltages are different than mine.
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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
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Like this (https://drive.google.com/open?id=0BzpaeXutpVmJbVJZTWw4U2ZDQTg)
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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
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I think you should use this link where you will get best solution with step by step.
http://lcdrepair.co.in/ (http://lcdrepair.co.in/)
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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?
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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
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Hello again . Only use these transformers to check the LED strips once I have opened the panel up and can test each strip individually
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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 (https://www.badcaps.net/forum/showthread.php?p=766568#post766568).
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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.
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Re your attached image, yes, that is exactly right. That will hopefully stop the SOS signal from reaching the microprocessor and affecting the backlights
operation. So in your case, did the backlights continue flickering?
RE THE badcaps post, it only refers to backlighting that uses CCFLs (cold cathode fluoro lamps), a different technology that uses long thin fluoro lights in lieu of LED strips. So not applicable in your case.
Hate to say it, but your problem is looking more and more like faulty LED or LEDs inside the panel. Bruce
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Re your attached image, yes, that is exactly right. That will hopefully stop the SOS signal from reaching the microprocessor and affecting the backlights
operation. So in your case, did the backlights continue flickering?
RE THE badcaps post, it only refers to backlighting that uses CCFLs (cold cathode fluoro lamps), a different technology that uses long thin fluoro lights in lieu of LED strips. So not applicable in your case.
Hate to say it, but your problem is looking more and more like faulty LED or LEDs inside the panel. Bruce
:73: Tried again nothing happened.
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Well, I think its time for examining the LEDs and wiring inside the panel. Bruce
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Well, I think its time for examining the LEDs and wiring inside the panel. Bruce
Hey can I check various Test Points on backside of LD-Board. I mean I cannot check them while it is mounted on back of TV. If I unscrew it and put it on table with everything connected can I measure the voltages at Test Points(labelled as TP#### see the Image). Would it cause any damage because Ground screws are removed frm the board.
If I can, then where should I put the black probe of multimeter on metal chasis or somewhere else.
Also another question if the LED(Backlight) is disconnected from the LD-Board then why do the voltages at LD3 keep flickering in same pattern with Backlights.
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Yes, you can check the LD board thus. It will still have ground connections through LD1 back to the power board. Use metal chassis as your ground for measurements.
You make a valid point about unplugging LD3 and the voltages still fluctuate. Can only assume that the LED sensing on the LD board sees there is no LED current and sends the SOS back to the main board.
Have you tried the self-check mode as per service manual. This also acts as a factory reset when you exit the mode. Not sure if it'll achieve anything in your case, but it's worth a shot. Bruce