Toshiba 58L1350UC Backlight.

[tantogata]

Symptoms: turn the TV on - short white flash screen and black. Flashlight test showing an image on the black screen. Power light is on (green light). I've red a "A guide on how to troubleshoot 2 seconds to black" but before to start to follow this guide may be someone got the same experience with that model of the TV and give me some additional advice. Thanks.
P.S.
After moving (shaking) and didn't operate the TV for several days it starts to work properly for 10-15 minutes and go black screen again.

[neilc6]

Re: Toshiba 58L1350UC Backlight.

On Toshibas, bad backlights can damage the power supply and vice versa. So if you install new strips, they can be instantly be damaged again. Do not recommend repairing these models for this reason since you will spend more money trying to repair than the tv is worth.

[nomoresonys]

Re: Toshiba 58L1350UC Backlight.

check over your solder joints, just in case its something simple like that, examples of bad joints there: https://www.google.com/search?q=bad+...ih=607&dpr=1.5

[nomoresonys]

Re: Toshiba 58L1350UC Backlight.

check the big capacitor C601, carefully VERY HIGH VOLTAGE THERE, meter set to dcv probe on each leg, see what voltage you get with tv powered on. If its around 400 or so, then maybe take it down to the backlights and check them and their connections, refresh rate for this one is 120, a lot of gamers like that.

[nomoresonys]

Re: Toshiba 58L1350UC Backlight.

maybe check the electrolytic capacitors around the P802 connector.

[tantogata]

Re: Toshiba 58L1350UC Backlight.

Everything looks perfect
https://imgur.com/a/VFDR5l6
355V. on C601 capacitor. The electrolytic capacitors around the P802 connector look like new.
Looks like the issue is in backlight strip. Right?

[tantogata]

Re: Toshiba 58L1350UC Backlight.

I've checked LED strips - work fine (125-130V. for 23 LED in one line, there are 5 lines, no one died, around 5,5V for one LED, is it OK?).
Measurements on LED connector (P803 on power board, from 0-1,5V. between LB1-/LB2-/LB3-/LB4-/LB5- and LB1+/LB2+/LB3+/LB4+/LB5+ with/without connection LED strips, power TV on). BUT if I put negative lead on ground and positive one on LB1+/LB2+/LB3+/LB4+/LB5+ I get 120V.
What I did: checked all diodes, LED strips, voltages on P803 connector. The diode (D201) is strange. When I'm checking on the board it passing test in both side. When I took it out and check again the diode passing test only one way (as normal). The fuse is OK.

[tantogata]

Re: Toshiba 58L1350UC Backlight.

I'm confused, all symptoms tell that I have dead led strips but I've checked them with a backlight tester, no one was dead. Is it possible if even all led strips pass test they still have an issue?

[nomoresonys]

Re: Toshiba 58L1350UC Backlight.

could be, most backlight testers do not supply the current that the powerboard does, so they could be failing at the higher current, but backlight testers are still a great tool imo, they have saved me many hours of troubleshooting by just showing me the screen had a slight crack, that could only be detected by lighting up the screen.

[tech9pc]

Re: Toshiba 58L1350UC Backlight.

You can also try testing each LED individually ... if you see any that are working but are dimmer than the rest .. replace them.

[tantogata]

Re: Toshiba 58L1350UC Backlight.

I'm not sure, please clarify a question: I have 0 volts between LB1- and LB1+, LB2- and LB2+, and etc. (TV is on, disconnected LED wires). Is it normal? I think it must be around 120 volts like to between ground and LB1+, and etc.

[tantogata]

Re: Toshiba 58L1350UC Backlight.

Some guys recommend to measure voltage for LED strips between LB1- and LB1+ on the connector, the others between "ground" and LB1+. Who is right? I'm confused.

[tantogata]

Re: Toshiba 58L1350UC Backlight.

If I unplug the TV for a long time (several days), the TV is working untill next turn on/off. I've changed a powerboard but the problem is still there.

[lotas]

Re: Toshiba 58L1350UC Backlight.

The problem may be not only in the LEDs, but also in the connectors on the strips themselves (no contact, burning, poor soldering, cracks).

[lotas]

Re: Toshiba 58L1350UC Backlight.

Some guys recommend to measure voltage for LED strips between LB1- and LB1+ on the connector, the others between "ground" and LB1+. Who is right? I'm confused.

You should always measure between LB1- and LB1+, because on LB1+ it is always present relative to gnd, and LB1- is controlled by driver led and mosfets.

[tantogata]

Re: Toshiba 58L1350UC Backlight.

I've changed a main and power boards but the problem is still there. I've checked LED connectors, they are ok. All LEDs light well, I've checked them with my LED tester. Now I'm thinking to change T-CON board - the last board on the TV which I didn't change yet. If this not help to fix the TV it will be interesting.

[nomoresonys]

Re: Toshiba 58L1350UC Backlight.

First post, you state flashlight shows an image, MOST times this means a backlight issue, could also be powerboard issue, usually I like to prove the backlights and powerboard before moving on to mainboard or tcon or panel.

[nomoresonys]

Re: Toshiba 58L1350UC Backlight.

"I've checked LED strips - work fine (125-130V. for 23 LED in one line, there are 5 lines, no one died, around 5,5V for one LED, is it OK?)." what does that mean? if it is different than the rest it's a backlight issue, when you are able to turn the tv on, set the backlights or brightness way down, then see if tv stays on longer.

[tantogata]

Re: Toshiba 58L1350UC Backlight.

All 5 led lines light shine with led tester. No one single led died. When the TV is turning on LEDs is short flashing and that's it. After long period of time (a week and more) not operating the TV, it is turn on and works for long time (I dodn't know how long cause I've tried to turn off and on the TV but on second time turning the TV was failed).

[nomoresonys]

Re: Toshiba 58L1350UC Backlight.

Are you saying that you tore it down and looked at/tested every single led?