(VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

[Folxs]

Hi, I have Toshiba 40L3448DG, made by VESTEL, and backlight is ok, it normally operates by switches (turn on, turn off) but there is no picture on the screen.

Whole TV takes about 35W, I unplugged backlight and MB takes about 10W and normally turn on/off so I think this is working properly.

Fuse on T-CON is ok, i tried to find shorted cap on it - but all seems to be ok.

Any ideas?

[budm]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

What do you see on the screen if you only have one ribbon cable between the T-CON and the LCD panel connected one at a time?
There are also may Voltage test points on the T-CON board that you need to test, I.E. AVDD, HAVDD, and many more.

[dick_barton]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

What voltage do you have at the fuse on the tcon?

[Folxs]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

What do you see on the screen if you only have one ribbon cable between the T-CON and the LCD panel connected one at a time?
There are also may Voltage test points on the T-CON board that you need to test, I.E. AVDD, HAVDD, and many more.

I tried only on left and right ribbon cable - same story on both, just backlight + dark screen.
Some measurements:
AVDD: 0.044V
HVIN_12V: 0.428V
B_INT_DCDC: 0.004V
VIN_12V: 12V

ICD2_VCC_1.8V: 1.8V
INV_V: 1.65V
FB_TRDY_3: 3.25V
FB_TRDY_1: 3.25V
FB_R: 0.004V

Definietly something wrong on HVIN - what can this cause? (EDIT: On last photo i did some black arrows, where that via is going)

What voltage do you have at the fuse on the tcon?

12V

[budm]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

I would check to see if the HVIN goes to the fuse or not, then check the resistance between HVIN and GND to see what you get.
Pictures of the backside of the T-CON so you can see where the vias go to.

[Folxs]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

I would check to see if the HVIN goes to the fuse or not, then check the resistance between HVIN and GND to see what you get.
Pictures of the backside of the T-CON so you can see where the vias go to.

There is no short.

Can't find second fuse or something like that.

I did red arrows to show where that via is going.

This could be bad RT6921, or something in his area? Or could it be bad mainboard, that doen't communicate with that IC?

[budm]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

It is hard for me to see where the trace go into without having the board in front of me.
You can look for the spec sheet of the RT6921.

[Folxs]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

This IC is pretty rare and hard to find / expensive.

I'm wondering if I can just send 12V by connecting VIN to HVIN? <devil> But probably this is stupid idea

[budm]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

That HVIN goes to another IC for reason instead of going directly to the 12V in for reason. Did you look to see what the replacement T-CON board will cost?

[lololatte]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

Hey Folxs did you manage to find the fault? i have the exact same symtons and measurements... on another monitor but they are using the same tcon components. greetings

[ph4t3]

Re: (VESTEL) Toshiba 40L3448DG - backlight ok, but no picture

looks like there is a damaged connector on the video board.