Help with no backlight on Toshiba 42AV504D

[budm]

Re: Help with no backlight on Toshiba 42AV504D

What DC voltage do you have on the pin 12 (on/off) of CN2 MASTER Inverter board when TV is off and when TV is ON?

[Mikeyboy2007]

Re: Help with no backlight on Toshiba 42AV504D

4.94v on pin 12 budm

[budm]

Re: Help with no backlight on Toshiba 42AV504D

OK, so you do have all the needed signals. More in depth troubleshooting of the inverter boards then.
BTW, does one of the flat ribbon cable on the MASTER INverter board go to the T-CON board?

[Mikeyboy2007]

Re: Help with no backlight on Toshiba 42AV504D

yeah mate sure does. thought that was pretty strange. one ribbon from master inverter goes to tcon and the other to the slave inverter.

[budm]

Re: Help with no backlight on Toshiba 42AV504D

Remove that cable to the T-CON and see if the backlights will come on, I believe it is part of the Dynamic dimming control so they can claim high contrast ratio.

[tom66]

Re: Help with no backlight on Toshiba 42AV504D

It is BACKLIGHT SYNC - for reducing screen flicker and improving motion response. Screen goes black while it is being updated.

[budm]

Re: Help with no backlight on Toshiba 42AV504D

It claims to have 17,000:1 Contrast ratio.
http://toshiba42av504d.fullhdtvs.co.uk/

[tom66]

Re: Help with no backlight on Toshiba 42AV504D

Complete nonsense, no LCD can achieve that. Highest (ACTUAL figure, not marketing figure) is about 2000:1 for some high end 4K Sharp LCD panel.
The best plasmas achieve around 30,000:1.
AMOLED achieves >1,000,000:1

[budm]

Re: Help with no backlight on Toshiba 42AV504D

They did that by using active dimming control just to fool the people to make you think you have high contrast ratio.
I.E.:
http://www.cnet.com/news/contrast-ra...r-lies-to-you/

[tom66]

Re: Help with no backlight on Toshiba 42AV504D

Yeah, they basically measure the full-screen black (backlight 10%) vs full screen white and claim that as contrast. In reality a scrolling checkerboard should be used and that generates valid contrast ratios.
But it's the same as "marketing GHz" or "marketing watts" (audio amplifiers, inverters, power supplies, etc.) - more is better!

[Mikeyboy2007]

Re: Help with no backlight on Toshiba 42AV504D

budm removed the ribbon from T-Con to inverter and still no backlight.

[Mikeyboy2007]

Re: Help with no backlight on Toshiba 42AV504D

Any ideas ?

[budm]

Re: Help with no backlight on Toshiba 42AV504D

You can try new set of inverter boards.

[Mikeyboy2007]

Re: Help with no backlight on Toshiba 42AV504D

will do budm, will order some from ebay and let you know how it goes.