led backlight voltage issue on Toshiba 32W3453DB

[edoogle]

Hey guys,

Im trying to fix a backlight issue on my sisters Toshiba 32W3453DB

after watching several youtube videos, I jumped in at the deep end and started replacing led's I thought were bad, but with no success.

after testing the 17IPS11 power board, I was only getting 25v out on the led supply so replaced this but Im still getting the same issue.

I dont have the voltage info from the power board to the main board so I'm struggling to diagnose the 17MB95 23186905 but I fear this could be the issue?

does anyone have the voltage to pin info for the connection from power to main board please

Thanks

Kev

[dick_barton]

Re: led backlight voltage issue on Toshiba 32W3453DB

If you disconnect the led connector from the power supply can you check what voltage you have at the led connector pins. It should spike high then quickly fall back.
Also some clear well focused photo's would be helpful.

[budm]

Re: led backlight voltage issue on Toshiba 32W3453DB

We do not know which version of the power supply board you have.
See PDF schematics.
Pictures of the boards and the whole backside of the TV showing all the boards will help.
There are also threads about 17IPS11:
https://www.badcaps.net/forum/search...rchid=12931643

[edoogle]

Re: led backlight voltage issue on Toshiba 32W3453DB

Thanks for the schematics,

I tested with and without leds connected and got same voltage, no spike at all

Ive attached some images, and will start to check voltages to mainboard

Is there anything else worth looking at?

Thanks again

Kev

[budm]

Re: led backlight voltage issue on Toshiba 32W3453DB

Right now you are see the 24V at the LED connector because the Boost converter circuit is not working which can be due to the circuit fails or because BL-ON-OFF is not present. You should monitor the BL_ON-OFF pin to see if it changes state when you turn TV on and off. You should verify that all the control signals are present first.
BTW, the schematics are the master schematic which will show ALL the component to create the net-list to make the blank PCB, the blank PCB then will be stuffed with the needed component for particular PCB Assembly.

[Diah]

Re: led backlight voltage issue on Toshiba 32W3453DB

can you hear sound ? did you test it with torch light? that you can see picture on the LCD ??

[Kg74]

Re: led backlight voltage issue on Toshiba 32W3453DB

Did you check for a short in any of the wires going to the LEDs? I just dealt with a problem on a Westinghouse and after tearing apart the panel and testing every LED as well as checking all the voltages which appeared correct luck shined my way. On a final assembly I had picture - my conclusion was a short in the wire which I taped up and since then no issues.

My theory is the screen would power on, sense the short and the protection circuits kicked in. Easy to check.

[edoogle]

Re: led backlight voltage issue on Toshiba 32W3453DB

Thanks guys, yes it was typical sound working, torch show lcd image present no backlight, as for shorting the voltage is same with or without leds connected so that rules that one out.
I am getting 3.3v at the bl-on/off

[Diah]

Re: led backlight voltage issue on Toshiba 32W3453DB

Thanks guys, yes it was typical sound working, torch show lcd image present no backlight, as for shorting the voltage is same with or without leds connected so that rules that one out.
I am getting 3.3v at the bl-on/off

after watching several youtube videos, I jumped in at the deep end and started replacing led's I thought were bad, but with no success.

your first work to replace LED some things wrong there. take the screen out and keep it out of the set until you have working complete led BL. show us photo on your work before and what kind of LED

[edoogle]

Re: led backlight voltage issue on Toshiba 32W3453DB

your first work to replace LED some things wrong there. take the screen out and keep it out of the set until you have working complete led BL. show us photo on your work before and what kind of LED

Thanks Diah, I've already replaced both LED rails, and the power board

an interesting thing happened today, I removed both boards from the chassis and wired them up and for about 3 seconds the led bl came on, but this happen intermittently therefore Im lead to believe its a bad solder joint somewhere as I did manage to get it to stay on permanent but when the board is moved this disturbs the bad joint

[budm]

Re: led backlight voltage issue on Toshiba 32W3453DB

If the LED's did come on that means the boost converter did work, but now it probably comes on and then shutdown due to no load so all you get is the 24V feeding Voltage.