Sony Bravia 55 KDL-55EX640 no backlight / flashes once

[budm]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

Well, one way to be sure is to have spare LED strips (4) to verify. We do not have the diagram to really dig deep into component level on the board, other than that you can buy the board and take a chance that it will fix the problem. From what I have seen in other threads regarding to the LED backlights TV, common failures are in the LED strips not in the LED driver board.

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

where can i get the spare LED strips? the client might be convinced to buy these to do the test before buying the psu which is 90 dollars
would i have to take apart the panel to find out which LED strips i need to buy to test with?

[Ltank]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

LED steps are considered part of the screen. Most Recyclers
Remove boards and discard the screens. Too time and labor to disassemble the screen s

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

so basically they cant be found unless i get lucky and find the same exact TV with a cracked screen?

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

and is buying a new panel even an option? the TV is worth 900$ as far as i can tell

[Clydeuk]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

Not many TV's can justify the cost of a replacement panel, these are generally priced as expensive as the entire set, sometimes more than the set cost.

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

yeah thats what i was figuring. i cant find anyone selling a panel for it. gonna try get them to buy this one with a cracked screen on ebay for 150$ and swap the boards. and if that doesnt work, then swap the LED strips.

what im more irritated about though is why i was not able to see any amps going to the backlight (even though i know it was getting current because i saw it flash)

i tried it with my analog meter as well and saw no change in the needle except when i put it on the lowest setting (.5 miliamps)
and even then the only thing the needle did was slightly deflect to the left (what does that even mean???)

[budm]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

If the analog meter deflect to the left then you need to reverse the probes. Also are you saying all four wires none of them show activity?

[budm]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

"This might work, you can have just one of the four wire connected and see which one does not show a flash of backlights for seconds, you should observe it in dark room."
Did you do this test as I suggested?

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

yeah that is exactly the test i did. with just one wire at a time, both white wires wont make a flash no matter what pin i put them in. the black and blue wires will make a flash on any pin, but if i turn off and restart the tv the flash gets dimmer and dimmer until i cant see it at all (even in a completely dark room) only with the black wire on pin3 do i get consistent backlight flashing. is there a way i can bypass the system's need, or trick the other pins into thinking they are drawing current so i can just power one LED strip at a time without it going into auto shutoff mode? i know it will be dim but at least it would show something...
dont know why they cant set it up that way to begin with. this "one goes out they all go out" shit is BULL


details of the testing i did were in post 37

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

please... " is there a way i can bypass the system's need, or trick the other pins into thinking they are drawing current so i can just power one LED strip at a time without it going into auto shutoff mode? "

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

someone on Ebay is offering to sell me the strips for 125 plus shipping. that seems like way too much... is it?

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

little help? please

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

why has this thread seemingly died on the operating table??? not to be a squeaky wheel but i only have so much space in my house for dead TV's...if i dont fix some of these and get em out i wont have room to fix any more!

[budm]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

To simulate the LED strip, we will need to know how many LED there are on the strip to get the total voltage drop on the string, then you may able to calculate the resistor value based on Guessing the driving current the LED string is using. So unless you know how many LEDs you have in the string you will not be able to use the resistor as the dummy load. You will have to take the panel apart to get to the LED strings. Right now per your test in post 37, you do have two bad strings so I do not see any reason to go further and since the LED string is not cheap, two already gone out, so the other will more likely to go out later. So is it worth spending lots of money on USED LED strips?

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

i can get all 4 strips from a guy named marcos on ebay for 100 bucks he says... that could be worth it, right?
ive asked him how many LED are in the strip so i can make this resistor test you speak of.
i know it seems like i do have 2 bad strips for sure but i would still like to see if i can make the other 2 light up on their own.

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

also this is for a client and i think they would be willing to pay 100 for a chance at fixing this tv

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

Salesmarcos never did get back to me with how many led per strip so I had to ask someone else...he said there are 7 led per strip. So how do I make the dummy resistor using this knowledge?

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

well i went ahead and bought some LED strips from the other guy on ebay "patch1stripe" who actually was nice enough to tell me there were 7 on each strip.
however, he listed the item as NEW
and when i finally got it, i notice one of the strips is missing an LED!
i already sent him a message about it. because obviously they are not NEW!

the other troubling thing is that while i thought we had decided that i should only have 4 LED strips in this panel,
he sent me pairs enough to make 7 strips!
without having opened the panel i have no idea now how many strips there actually are in there but 7 cant be right, can it?

oh and also, i was hoping they would come with the wiring so i could just plug them directly into the power supply without opening the panel, but they are just the strips!

is there a way i can hook these up externally to test my internal LED strips?
and howabout trying to make a dummy load with some resistors based on what we now know about these LED strips?

please help!

[triplefour]

Re: Sony Bravia 55 KDL-55EX640 no backlight / flashes once

boy its awful quiet in here....