Toshiba 58L4300U Flashes logo no picture.

[fcisolutions]

Hello I have a Toshiba 58L4300U. When I hit the power button the toshiba logo flashes and the backlights flash and thats it. Lights cut off t.v. is then non responsive.

Voltage readings on connection P802 are

Pin 1 = 1.8V
Pin 2 = 5.23V
Pin 3 = 3.4V
Pin 4 = 3.2V
Pin 5 = 3.5V
Pin 6 = 5.1V
Pin 7 = 0.0V
Pin 8 = 0.0V
Pin 9 = 0.0V
Pin 10 = 12.3V
Pin 11 = 0.0V
Pin 12 = 0.0V
Pin 13 = 12.3V
Pin 14 = 12.3V
Pin 15 = 12.3V

[dick_barton]

Re: Toshiba 58L4300U Flashes logo no picture.

The voltages all appear fine. Could well be a led or led driver fault. Photo's of your boards and how they interconnect would be helpful?

[Andrew F. Ali]

Re: Toshiba 58L4300U Flashes logo no picture.

Could you repost the voltages you got on P802 but this time with the Pin Nos. AND the labels? So for instance, when I see Pin 2 = 5.23V (StdBy)

[fcisolutions]

Re: Toshiba 58L4300U Flashes logo no picture.

Pics of the board.

[Andrew F. Ali]

Re: Toshiba 58L4300U Flashes logo no picture.

OK. After viewing the pin#4 and being able to identify voltages, I suspect a bad LED backlight issue.

[budm]

Re: Toshiba 58L4300U Flashes logo no picture.

You have 5 LED strings.
Put meter in 200VDC scale.
1) TV off, keep the black probe on the chassis.
2) Keep red probe on 'LB1-)
3) Turn the TV on while watching the meter to see how high the Voltage goes up to.
4) Repeat step 1 ~ 3 but move the red probe to 'LB2-'.
Do the same on 'LB3-' ~ 'LB5-'.

[fcisolutions]

Re: Toshiba 58L4300U Flashes logo no picture.

150.3 on each one.

[budm]

Re: Toshiba 58L4300U Flashes logo no picture.

That is very high.
So when you turn on the TV you see the backlights flash on and the reading jumps up to 150V they stay there even after the lights go out?
Notes: It cannot be 150V on the (-) minus pin when the backlights come on.
You are measuring at the LB1 ~ 5 (-) pins, correct, not the LB1 ~ 5 (+) pins.

[fcisolutions]

Re: Toshiba 58L4300U Flashes logo no picture.

Yes sorry I was measuring the +.
On the - side it is
LB1 = 47.3
LB2 = 48.2
LB3 = 37.9
LB4 = 43.8
LB5 = 44.2

[budm]

Re: Toshiba 58L4300U Flashes logo no picture.

Yes sorry I was measuring the +.
On the - side it is
LB1 = 47.3
LB2 = 48.2
LB3 = 37.9
LB4 = 43.8
LB5 = 44.2

So to be sure we are not getting wrong data, those Voltages are made per instructions?

[fcisolutions]

Re: Toshiba 58L4300U Flashes logo no picture.

Yes they were.

[budm]

Re: Toshiba 58L4300U Flashes logo no picture.

LB3 does not look right compared to the other 4.

[fcisolutions]

Re: Toshiba 58L4300U Flashes logo no picture.

I agree so possible backlight strip failure, you think?

[budm]

Re: Toshiba 58L4300U Flashes logo no picture.

Yes, this where the LED backlights tester come in handy because it will give the Vf (Forward Voltage) reading of each LED string.

[fcisolutions]

Re: Toshiba 58L4300U Flashes logo no picture.

Yes I have a backlight tester. They are all at 124 except LB3 which is at 129.