Toshiba 32W1333DB no backlights

[Nevillet]

Hi,

I have a Toshiba 321333DB with a Vestel 17IPS11 power board.

The TV powers up but the backlights do not light.

If I externally power the LED's I get a picture.

Any pointers?


Vestel 17IPS11 Schematic linked below:
https://www.badcaps.net/forum/attach...1&d=1614948277

[dick_barton]

Re: Toshiba 32W1333DB no backlights

Check your BL_ON voltage level at power up.

[Nevillet]

Re: Toshiba 32W1333DB no backlights

When the set is on it's reading 3.26V

[dick_barton]

Re: Toshiba 32W1333DB no backlights

Do you have the 24V, 12V and 5V supplies? How about VCC pin 16 of U103.

[Nevillet]

Re: Toshiba 32W1333DB no backlights

Measuring at CN100
Pin 1 = 23.6V
Pin 5 = 5.3V
Pin 13 = 11.9V

U103
VCC (pin 16) = 5.9V

[dick_barton]

Re: Toshiba 32W1333DB no backlights

Did you mean pin 15 (VIN) = 11.9V
Does D107 cathode voltage peak sharply and drop when you come out of standby?

[Nevillet]

Re: Toshiba 32W1333DB no backlights

U103
Pin 15 = 9.3V in standby > 11.9V when on (it seems stable between the 2 states and not jumping around)

[dick_barton]

Re: Toshiba 32W1333DB no backlights

Everything appears to be in order so far.

Is U103 pin 16 at 6V when out of standby.

What was the peak voltage at D107 cathode when switched out of standby.

[Nevillet]

Re: Toshiba 32W1333DB no backlights

U103 pin 16 is 5.9V when out of standby (TV on)

D107 Cathode is 22.3V

[Nevillet]

Re: Toshiba 32W1333DB no backlights

Back tomorrow

[dick_barton]

Re: Toshiba 32W1333DB no backlights

The led driver chip is not boosting the incoming 22.3V to drive the leds.
Check the diode D107, D138 & D110 using your multimeter in diode mode and also the mosfet Q103, transistor Q110 and R187. There are plenty of videos on Youtube showing how to test the components.

Check this video out https://www.youtube.com/watch?app=desktop&v=RxwdC7V5Ue0