SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

[mykolas]

Morning all,

Have the above model that had the led strips replaced by me. Second set ordered and I need information on how to lower the current to the led"s. I've done this to other sets using current limiting resistors and the sets have been fine for 4 years. The problem is that Sharp barely recognizes this model and bestbuy just wants the set in their shop. The power board:

715G8095-P01-000-0035(board number)
pltvfy751aau4/fy751aau4(sticker number)

I traced from the the led socket and it goes to two 8 pin chips. Can't see any current limiting resistors(possibly they are smd's). Hoping maybe someone has gone thru this before with Sharp sets or possibly download a schematic with ideas that will help me.


Thanks for looking,


Mykolas

[nomoresonys]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Check tomtech here, he has at least a few where he's done a current mod, this one was the easiest. I don't know if he's done your exact model: https://www.youtube.com/watch?v=dnTz41ot8-s

[nomoresonys]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Tom's good, here's his fix it playlist those mods are in there, I saw at least 3 for backlight current mods, simple procedure actually and he explains it pretty well: https://www.youtube.com/watch?v=GrfS...gtd-hcUXG2KjSC

[mykolas]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Thank you sir. Great tutorials. Will keep looking for the schematic and apply what I learned here.

Thanks,


Mykolas

[budm]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Can I see good clear straight shot of the whole top and bottom sides of the power supply board?

[mykolas]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s




Got the schematic. Page 61 has the led configuration


Mykolas

[mykolas]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

I believe resistance network r8607-r8615 would have to be increased. Am I right about this? Is there any other circuit that would need to be changed at the same time?


Thanks for any insight,


Mykolas

[nomoresonys]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Looks like mostly they just raise the resister value which lowers the current.

[mykolas]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

I'm trying not to guess at this point. I've already changed one set of strips and would like to lower the risk of the chance of replacing another.
Anyone have an idea what to change and why?


Mykolas

[budm]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

I believe resistance network r8607-r8615 would have to be increased. Am I right about this? Is there any other circuit that would need to be changed at the same time?


Thanks for any insight,


Mykolas

What page of the service you ref those resistors to?
Page 56? I do not see R8607 ~ 8615, that's 9 resistors?
Is LED controller IC U8601 (PF7708AS) used on your board? I would look up the spec sheet on that.

[mykolas]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

I'm sorry, the resistor network is located on pg. 61.


U8601 is : PF6002AS so far can't find data sheet.



Mykolas

[mykolas]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

I think there is a bit of confusion here. The schematic is for three different power boards. Page 56 and 58 are for 32" and 43". They basically use the same IC U8601. Page 61 is for the 50". Completely different circuit.



Mykolas

[budm]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

You have two LED strings and two LED controller IC's TPV101AD U805 and U806.
Pin 6 (ISET) is for setting the current for the LED string by adjusting the value of the resistors attached the ISET pin.

[neilc6]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Just got this TV replacing 3 bad strips with used ones I had. The default backlight level is labelled TV Brightness and defaults to Brightest (max) after doing a factory reset. Some leds sit in cavities in the chassis so may not get the best heatsinking if floating in the air. I think the combination of these two issues are causing LED failures on this model.

[budm]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Did you take lots of good pictures? OP did not provide any pictures for this TV model, thanks.

[neilc6]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

No pictures of the back but pictures of how the leds sit on top of the cavities.

[mykolas]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

I've added sticky aluminum muffler tape under those open leds. Cut into strips and can attach ends to chassis. But I believe the current reduced is the best option for lasting.
Can't figure out what to change to reduce the current on this circuit.
Could use some direction here.


Mykolas

[budm]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

I've added sticky aluminum muffler tape under those open leds. Cut into strips and can attach ends to chassis. But I believe the current reduced is the best option for lasting.
Can't figure out what to change to reduce the current on this circuit.
Could use some direction here.


Mykolas

Did you not read post #13?

[neilc6]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Plaiyng more with the settings on this tv, backlight level is set under Advanced Picture Settings and most picture modes including stsndard run the backlight at 100% Even low power mode is at 78%. You need to turn off dynamic contrast which is default on to change the backlight level.

[mykolas]

Re: SHARP/BESTBUY LC-50LB481U Need to lower current to led"s

Thanks neilc6, I will check those settings.