Toshiba 50L4353D With 5 Bad Leds !

[flocko]

Re: Toshiba 50L4353D With 5 Bad Leds !

Not a good photo need part number of IC6 then look up data for the IC to see what pin is used for current setting then go from there ?

[vinceroger69]

Re: Toshiba 50L4353D With 5 Bad Leds !

Not a good photo need part number of IC6 then look up data for the IC to see what pin is used for current setting then go from there ?

Thanks flocko and reece for your help when i get some spare time i will take power supply out and get the number of the ic as ive got a few projects on and running out of space at the minute.I will update my own thread i started so it keeps it all in thread.

[Malachi]

Re: Toshiba 50L4353D With 5 Bad Leds !

Reecey, why was your led TV able to stay on with bad LEDs but mine, from the other thread turns of due to bad LEDs?
I'm just learning this stuff. Do different tv's behave differently?

[budm]

Re: Toshiba 50L4353D With 5 Bad Leds !

https://www.badcaps.net/forum/showpo...89&postcount=9
Look at the board layout, you can see that the board has 4 PWM controlled power MOSFETs (Q13~16) to control 4 strings of LEDs,'all the Source pins of all 4 MOSFETs are tied together to single current sensing resistor R159 (there are two SMD resistors (221) R131, 132 also connected in parallel with R159). The MOSFET next to the small blue cap C22 is for the boost converter circuit
So to reduce the current you will have to increase the value of R159 but you can increase it s much before it is out off the control range of the circuits as designed.
You can measure the VDCdrops on the R159 with True R.M.S meter to see how much current is flowing at max backlights setting.

[ReeceyBurger123]

Re: Toshiba 50L4353D With 5 Bad Leds !

Thanks flocko and reece for your help when i get some spare time i will take power supply out and get the number of the ic as ive got a few projects on and running out of space at the minute.I will update my own thread i started so it keeps it all in thread.

No worries mate, sorry for no reply I had a mate over. Will read thread now.

[budm]

Re: Toshiba 50L4353D With 5 Bad Leds !

Reecey, why was your led TV able to stay on with bad LEDs but mine, from the other thread turns of due to bad LEDs?
I'm just learning this stuff. Do different tv's behave differently?

BTW, your TV did not turn off in your thread since all the power supplies are still running, only the backlights shut off due to the protection circuit detects open LED connection, the TV was still powered up.
https://www.badcaps.net/forum/showthread.php?t=52749

[ReeceyBurger123]

Re: Toshiba 50L4353D With 5 Bad Leds !

Reecey, why was your led TV able to stay on with bad LEDs but mine, from the other thread turns of due to bad LEDs?
I'm just learning this stuff. Do different tv's behave differently?

Some have very sensitive controllers for example sharp Tv's flash an error if an Led is out and the controller shuts down. This Tv and like many others I have fixed if not all them dont really care and will still run the rest of the Tv even if the Bl has gone out.

[ReeceyBurger123]

Re: Toshiba 50L4353D With 5 Bad Leds !

https://www.badcaps.net/forum/showpo...89&postcount=9
Look at the board layout, you can see that the board has 4 PWM controlled power MOSFETs (Q13~16) to control 4 strings of LEDs,'all the Source pins of all 4 MOSFETs are tied together to single current sensing resistor R159 (there are two SMD resistors (221) R131, 132 also connected in parallel with R159). The MOSFET next to the small blue cap C22 is for the boost converter circuit
So to reduce the current you will have to increase the value of R159 but you can increase it s much before it is out off the control range of the circuits as designed.
You can measure the VDCdrops on the R159 with True R.M.S meter to see how much current is flowing at max backlights setting.

Awesome, will also help me when messing about with one of them too. Cheers bud

[budm]

Re: Toshiba 50L4353D With 5 Bad Leds !

Awesome, will also help me when messing about with one of them too. Cheers bud

Most if them will have individual current sensing resistor for each string, so the cheap one has one common sensing resistor so if one of the FOUR string goes open and the circuit will still try to maintain the same constant current through the sensing resistor, that means the current of the three strings will go up (driven harder) to maintain the same total current when all 4 strings were working.
3 more resistors +misc parts cost more money.
You can also see that there is only ONE GATE drive for all 4 MOSFETs instead of true 4 channels backlights driving scheme.

[stereojohn]

Re: Toshiba 50L4353D With 5 Bad Leds !

Kind of funny my toshiba 50" also had 5 burnt leds and work great now !

[budm]

Re: Toshiba 50L4353D With 5 Bad Leds !

Just make sure to turn down that backlights level.
Sad isn't it that the LEDs never last as claimed due to bad implementation and cost cutting.

[ReeceyBurger123]

Re: Toshiba 50L4353D With 5 Bad Leds !

Yeah its very sad, Leds are brighter but keep them bright and they fail in no time flat. I have another 40" Toshiba on the way same fault bad Led's they are dropping like flies. On the plus side they sell in no time flat so im happy

I actually like fixing these Led backlights fixed 33 so far find it fun lol but there are many, many more to come !

Plasma all the way !