Vizio E470 LED current mod.

[dskall]

I have power board # 0500-0614-0270. Upper left is led ic9101. SEM5028 is chip number. I can find no pinout info. I would like to knock down current to led's. Anyone know how to id the pin for current feedback?

[petehall347]

Re: Vizio E470 LED current mod.

can it not be done in the service menu ? just a thought ..

[budm]

Re: Vizio E470 LED current mod.

It is 2-channels version of LED driver IC SEM5027 1-CH LED driver, so you just have to increase the resistance of the current sensing resistor connected to the Source pin of the two PWM controlled power MOSFET Q9105, 9205.

SEM5027 Diagram:
http://4.bp.blogspot.com/-80jXWtC6Hj...D%2BDRIVER.jpg

[dskall]

Re: Vizio E470 LED current mod.

So current isn't set at the IREF? There are 2 pairs of 30ohm at R9218/A and R9118/A are the ones you are talking about off Q9105/9205

[budm]

Re: Vizio E470 LED current mod.

Yes, you can use IREF too but I cannot find the pinout for this SEM5028.
Two 30 Ohms is parallel, 15 Ohms seems kind of high. Did you measure them. If you remove one of them then the current should drop in half.
I sure like to find the spec sheet of both ICs.

[dskall]

Re: Vizio E470 LED current mod.

I was surprised there was no datasheet. Removed one 30ohms. Have not tried it yet

[dskall]

Re: Vizio E470 LED current mod.

Ok update. The correct resistors are R9110 and R9210 which are 1.5ohm 1/2watt which output 420ma at max brightness. Replaced with 2 3.7ohm 1/4 watt in parallel. Which brought max. current to around 320ma. From what I find for led specs. is a max of 350ma. So this should bring current into reliable current ratings for led.

[budm]

Re: Vizio E470 LED current mod.

I would go down just a little more like 300mA or less and you probably will not see the different in brightness.
The max 350mA is probably at 25c but the temperature inside the panel will be higher than that so I would give it more head room by lower the current more..

[NeedsMoreFlux]

Re: Vizio E470 LED current mod.

scummy scammy manufacturers.

It is the higher voltage at start up that is the problem!

[budm]

Re: Vizio E470 LED current mod.

It is the constant current circuit so the maximum current will not be any higher than the set max current which these LED backlights TV are being driven at maximum current with no regard of the heat management or the life span.
This is the warning from LG spec. sheet for their own LED's:
※ Operating the LED beyond the listed maximum ratings may affect device reliability and cause
These or any other conditions beyond those indicated under recommended operating conditions
The exposure to the absolute maximum rated conditions may affect device reliability.

But guess how LG drives its LEDs in the LG panel.

[dskall]

Re: Vizio E470 LED current mod.

I think this is a way to do planned obsolescence. To kill them after the warranty.

[nomoresonys]

Re: Vizio E470 LED current mod.

I think this is a way to do planned obsolescence. To kill them after the warranty.

I think so too, why else would they do it, they must know that too much current is a killer.