Samsung UN46d6003SF screen dark some

[gavric]

Hello, i have another tread active and you guys are great.

I got this Samsung UN46d6003SF that has picture and everything works but image is kinda dark. I actually opened screen up and looked at led strips and they all light up. Edge lit screen from top, two strings of leds along top of screen only. No dead leds. I can stare at them and they are not bright bright. On power supply it says that power to led string TOP1+ should be 255VDC but i am measuring only 230V. I have measurements at led strip connectors as shown bellow:

BACKLIGHT ARE AT 20, multi-meter negative probe on tv chassis
TOP1+ 230VDC
TOP1- 111VDC
TOP2+ 111VDC
TOP2- 9VDC

Tv does respond to backlight level change and it gets darker to where at Backlight 1 TOP2- is about 134VDC.

Compared to working 46 samsung this one at full backlight level looks like good working one at level 4 i would say.

Picture of power supply is attached, provided by shopjimmy.

[budm]

Re: Samsung UN46d6003SF screen dark some

[SM].pdf&mfg=Samsung
If you disconnect the cable between the power supply board and the main board, are the backlights on brighter? Check and see if LED+1 is also still at 230VDC or not.
This one all the LEDs are connected in series, no zone dimming, etc. compared to your other LG.

[gavric]

Re: Samsung UN46d6003SF screen dark some

[SM].pdf&mfg=Samsung
If you disconnect the cable between the power supply board and the main board, are the backlights on brighter? Check and see if LED+1 is also still at 230VDC or not.
This one all the LEDs are connected in series, no zone dimming, etc. compared to your other LG.

I just unplugged main board from PS and backlights came on, about same in brightness and voltages are now as shown
TOP1+ 230VDC
TOP1- 115VDC boost of 4VDC from before
TOP2+ 115VDC boost of +4VDC from before
TOP2- 1VDC lost 8VDC from before

No increase in TOP1+ voltage to give me that 25VDC that I am missing from PS. I guess there in no current control circuit command from main board and that is why other voltages went up some, it that did not change anything regarding brightness. Tv seems to be like on 30% brightness I would say. Watchable but annoying.

[budm]

Re: Samsung UN46d6003SF screen dark some

Self-test mode (disconnecting the cable form the main) will put the LED driver circuit at full on mode (see explanation below). So you may have problem in the Voltage Booster circuit (IC9101, Q9101, D9102, L9101, C9110) that suppose to boost the Voltage up to 255VDC.

"TOP2- 1VDC lost 8VDC from before" Right now the PWM Controlled MOSFET Q9102 on the Cathode return side is basically fully on that is why you are only seeing about Vds drops of only 1VDC (same topology as other LED driver that I already explain how it functions and how it regulate the current flow through the LED in the your LG thread).

[budm]

Re: Samsung UN46d6003SF screen dark some

BTW, all other Voltages are OK? I.E. 5.3V, B13V, VAMP 12V?
Also what is thew PFC Boosted Voltage measured between the two legs of the main filter cap CP814S?

[budm]

Re: Samsung UN46d6003SF screen dark some

What is the LCD panel model number?
BTW, if you go into user OSD menu/?/Self Diagnosis/Picture test, does it look nice and bright?

[gavric]

Re: Samsung UN46d6003SF screen dark some

BTW, all other Voltages are OK? I.E. 5.3V, B13V, VAMP 12V?
Also what is thew PFC Boosted Voltage measured between the two legs of the main filter cap CP814S?

when tv is ON i get 392VDC at CP814S and when tv is off I get 164VDC.
all other voltages are good, 5v is 5.25v, 12v is 12,86V.

What is the LCD panel model number?
BTW, if you go into user OSD menu/?/Self Diagnosis/Picture test, does it look nice and bright?

screen model T460HW08 V.7
nothing changes by doing diagnostics, picture is at same brightness.


I read elsewhere that others have replaced IC9101 to fix no backlight problem where they had no voltage at all but in my case i am missing only about 25V.

[budm]

Re: Samsung UN46d6003SF screen dark some

What is the P/N of the IC9101?

[gavric]

Re: Samsung UN46d6003SF screen dark some

IC9101 is SEM5025