Toshiba 40D1333B no back light.

[Dang]

Hi, I have this Tv which has no back light, it is an LED type so was wanting to know how best to test for a bad LED strip? I've tested the PSU and think all voltages are fine, I'm seeing 24-25 volts from the supply caps so quite certain there's no short there, I've tested pins 1-12 for the back light with the connector disconnected and the last five pins show 24.5v, the first 3.2v and the second 1.4, with the connector back in place only pin 2 drops to 0.3v, the rest of the pins I believe are ground. My thoughts are for a shorted LED but I'm not to sure how to test for that without taking the screen apart, so my question is how? thanks, Andy.

[ReeceyBurger123]

Re: Toshiba 40D1333B no back light.

I have seen 2 other sets like this with either a samsung or Vestel panel and the leds themselves were bad, in some cases the connectors going to the leds can become weak and will need reseating and adding a small layer of tim on them could get them back and working. Best option would be to take apart the screen and check the leds normally when they fail there will be a crack in the optic glass on top of the diode.

[Dang]

Re: Toshiba 40D1333B no back light.

I have seen 2 other sets like this with either a samsung or Vestel panel and the leds themselves were bad, in some cases the connectors going to the leds can become weak and will need reseating and adding a small layer of tim on them could get them back and working. Best option would be to take apart the screen and check the leds normally when they fail there will be a crack in the optic glass on top of the diode.

Thanks for the info, if one or more are bad, what's the best course of action, can they be bypassed?

[ReeceyBurger123]

Re: Toshiba 40D1333B no back light.

Thanks for the info, if one or more are bad, what's the best course of action, can they be bypassed?

Normally you can just check the strip for a sort, if you see a cracked optic you can just break it off by wiggling it then check the diode.

[ReeceyBurger123]

Re: Toshiba 40D1333B no back light.

Here is an example of the bad led, from the photo you can see that the optic is cracked probably because the led shorted and got really hot.

[zomi]

Re: Toshiba 40D1333B no back light.

IS the crack next to the red line I added ?
Best to view these under a magnify lamp from the looks of it ?

[Dang]

Re: Toshiba 40D1333B no back light.

Here is an example of the bad led, from the photo you can see that the optic is cracked probably because the led shorted and got really hot.

OK, cool thank you, I have to ask though, would a bad LED take out just a strip or would it take them all out until replaced?

[budm]

Re: Toshiba 40D1333B no back light.

If they are connected in series, then it only need one open circuit to kill all the lights.
Can we see the pictures of the board? You can look at the connector and the circuits on the board to see how the LED strings are connected.

[Dang]

Re: Toshiba 40D1333B no back light.

If they are connected in series, then it only need one open circuit to kill all the lights.
Can we see the pictures of the board? You can look at the connector and the circuits on the board to see how the LED strings are connected.

Your right of course and I would have to say in series going by the power supply circuit although five 24.5v feeds threw the question. So from the top of the connector to the bottom, pins one and two are 3.2v and 1.4 respectively, the next five are ground and the bottom five are at 24.5v each, pin two drops to 0.3v when the connector is in place.

[budm]

Re: Toshiba 40D1333B no back light.

OK, let me analyze the board layout to see how the LEDs are connected.
OK, I cannot find anything at Shopjimmy to see if they have good pictures of the top and the bottom side of the board.
17PW07-2 power supply.
Can you please provide the pictures of the bottom side?
it looks like it has 4 LED strings (8 wires on the connector), 4 filter caps 1000uF/35V, so the drive voltage is not very high.

[tom66]

Re: Toshiba 40D1333B no back light.

Schematic of 17PW07-2:


Like all Vestel schematics it's drawn terribly...

[budm]

Re: Toshiba 40D1333B no back light.

OK, we are missing the LED driver board picture!
Can you upload the pictures of the whole back side of the TV.
That connector PL306 is just the output connector to feed 24Vdc, and backlights commands signals to the LED driver board.
TOM, thanks for the diagram.

[tom66]

Re: Toshiba 40D1333B no back light.

I have a sneaking feeling this is a TV with the 24V going to the panel, and the LED driver is inside the panel.
That's how the AUO panels in the 40L1333DB sets do it, and they use a very similar arrangement of parts.

[budm]

Re: Toshiba 40D1333B no back light.

Ah yes, I remember something like that now! IT IS SUCK BIG TIME.
https://www.badcaps.net/forum/showth...ght=LED+DRIVER

[tom66]

Re: Toshiba 40D1333B no back light.

What a wonderful design, and yet another example of a product designed to be non-serviceable. What would be the problem with sticking the driver on the outside of the panel? No problem at all, but for some reason it's done this way.

[Dang]

Re: Toshiba 40D1333B no back light.

What a wonderful design, and yet another example of a product designed to be non-serviceable. What would be the problem with sticking the driver on the outside of the panel? No problem at all, but for some reason it's done this way.

It hadn't eluded me, I guess it's time to take it apart. One last thing to add, I do hear a very high pitch noise on start up, not too sure what it is but might be a clue.

Just to add: this is a Samsung panel, and yes, it's a piece of crap but it's a friend's Tv so agreed to try and fix it, thanks.

[budm]

Re: Toshiba 40D1333B no back light.

Samsung panel with LED driver inside the panel?
Can you provide the panel model number sticker? I would like to look up an info for it.

[Dang]

Re: Toshiba 40D1333B no back light.

Samsung panel with LED driver inside the panel?
Can you provide the panel model number sticker? I would like to look up an info for it.

Here you go, picture attached.

[zomi]

Re: Toshiba 40D1333B no back light.

To fix you have to strip the panel

And get it like shown in the pic.

If you have full voltage across the inverter

Then you have to check for any blown led.

If all is fine its best to bridge the connections shown with solid wire and all should be well ..

Test it to see if any led's on verge of failing..

[ReeceyBurger123]

Re: Toshiba 40D1333B no back light.

To fix you have to strip the panel

And get it like shown in the pic.

If you have full voltage across the inverter

Then you have to check for any blown led.

If all is fine its best to bridge the connections shown with solid wire and all should be well ..

Test it to see if any led's on verge of failing..

The inverter will shutdown if it detects that an led isnt lighting and will only show 24v on the output. These panels are pure crap I have two more of these sets in now that need new diodes.