Very Nice Toshiba 46L5200U1 Strobe Effect

[Michale32086]

I seem to have very bad luck with Toshiba TVs...

Got this very nice Toshiba... Works fine for 5-10 mins and then the backlight starts strobing...

I had one a bit ago, same model, same problem. Broke that one down to the bare LED strip thinking that was the problem... But, after testing it, I am not so sure... Now I can't seem to find that one..

So, I wanted to eliminate other possibilities before I went that route with this one...

There are no burned or blowed caps or resistors.. Picture is fine for the few mins it's working...

Would this likely be an LED strip problem or a component/board issue??

[nomoresonys]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Did you try turning the backlights down and see if it stays on longer, thats a pretty good test for faulty leds, I think.

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Did you try turning the backlights down and see if it stays on longer, thats a pretty good test for faulty leds, I think.

I did not.. Thanx, I'll give that a shot..

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

OK thought I had something..

I turned the BACKLIGHT down.. TV came up.. everything was good.. Displayed the menu and inputs.. No problem.. Thought I had it made..

Plugged in a video source... Within seconds, it was strobing... Unplugged video source.. Display stabilized..

Main Video board issue??

[nomoresonys]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Was the video source thru hdmi or antenna/cable. guess I mean will it strobe on both inputs.

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Curiouser and Curiouser....

I hooked up a PS3 to HDMI 1... A DVD player was hooked up to COMPONENT before with the strobe..

Other than a flicker now and again at the start, it's playing flawlessly...

More and more pointing to the main board...

[nomoresonys]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Could be, seems like some mainboard inputs might be a little faulty, suppose it could just be a faulty component input, your component cables tested good on last use?

[budm]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

The Backlights is being controlled via T-CON board for dynamic contrast control (to give you the faked high contrast ratio spec.), what happen if you disconnect that cable between T-CON and the LED driver board, or disable the dynamic Contrast, dyna-lights control in the OSD user menu?

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

OK This TV is haunted.. It was working fine on the HDMI for like 5 mins or so.. Hooked up the COMPOSITE/COMPONENT again and it ALSO worked fine...

Then the backlights shut down, but I could still see the image with a bright light on the screen...

Shut the TV off, turned it back on.. Backlights came back up and then it started to strobe on both inputs....

I am hoping it's either the power PCB or the inverter board... As LED strips for this are not available outside of China...

[budm]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

See post 8.

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

The Backlights is being controlled via T-CON board for dynamic contrast control (to give you the faked high contrast ratio spec.), what happen if you disconnect that cable between T-CON and the LED driver board, or disable the dynamic Contrast, dyna-lights control in the OSD user menu?

Pulled the connector between the TCON and Driver board..

Same thing.. Strobe effect then backlights shut down..

[nomoresonys]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Might be time to test those pesky backlights, lol.

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

I was afraid of that..

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Thanx for the input guys... Was hoping for a board issue..

Oh well, sometimes ya get the bear, sometimes the bear gets you...

[budm]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Pulled the connector between the TCON and Driver board..

Same thing.. Strobe effect then backlights shut down..

How about if you disable the Dyna lights function?
And then turn down the backlights level to as low as possible to see what happen.
Then also check to see if the bl-on and PWM dim signals also go away or not when it acts up.

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

How about if you disable the Dyna lights function?
And then turn down the backlights level to as low as possible to see what happen.
Then also check to see if the bl-on and PWM dim signals also go away or not when it acts up.

I'll give that a shot.. Thanx...

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

OK.. DynaLight to OFF... Brightness and Backlights set to 25.... Dynamic Contrast is off...

Working good..

BLON is at 3.27 and can't find PWM, but there is a DIM pin and it's at 1V

I'll let it ride and check the voltages when/if it screws up..

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

OK ran it for about 10 mins.. Worked fine..

Slowly started bumping up the BACKLIGHT... Around 70 it started strobing and then after a few secs of strobing, the backlights shut down..

Gonna leave the BACKLIGHT at 50 and run it for a bit...

[Michale32086]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

Still craps out..

Does that support the LED strip being bad??

Or could it be the Driver Board??

[budm]

Re: Very Nice Toshiba 46L5200U1 Strobe Effect

It does sound like LED's problem.
LED driver board: You have 4 LED strings, each LED string Cathode is connected to one of the 4 the PWM controlled MOSFET's (Q101 ~ 401), you can check the Voltage on the big tab of each MOSFET to see if they are all about the same or not, the one with bad LED string should show different result.
The PWM dimming signals are from the T-CON board via CN002 connector on the LED driver board, there are pin names printed right by the connector.