samsung ue55ju6800 problem with brightness

[budm]

Re: samsung ue55ju6800 problem with brightness

According to SJ, the LCD panel is backlit, but since we do not have any pictures form OP, we cannot verify if that is true or not. Based on OP pictures, it looks like one set of the LED string is not driven the same as the other set of the LED string.
https://www.shopjimmy.com/samsung-bn...ght-strips.htm
https://www.shopjimmy.com/catalogsea...ung+ue55ju6800

[budwich]

Re: samsung ue55ju6800 problem with brightness

my "poor search" and "untrusted site"... shame on me...

I followed this:
https://www.displayspecifications.com/en/model/9db6434

[jjanssen7]

Re: samsung ue55ju6800 problem with brightness

This is fun, diagnosing his set without him being here! I'll weigh in again if I get another unit with this symptom.

[george_gpu]

Re: samsung ue55ju6800 problem with brightness

good day
wait for me , i will post new pictures

[george_gpu]

Re: samsung ue55ju6800 problem with brightness

Good afternoon
Sorry for delay reply
I take some photos







As you see from power supply to red connector(led bar) i have in first grey cable 310volt ,second gray 100volt and 3 grey 290 volt is that allright?

[budwich]

Re: samsung ue55ju6800 problem with brightness

I think you need to measure across the "+" to "-" as labeled... those are "driving pairs" for the backlights.

[budm]

Re: samsung ue55ju6800 problem with brightness

Your TV has two LED driver circuits, and two LED strings.
https://www.badcaps.net/forum/attach...4&d=1564065956
https://www.badcaps.net/forum/attach...7&d=1564065956
Do you see the two resistors (R9167, 9169) by the LED connector? As you can see, they are labeled for using as the test point, so with the TV turned off, keep the DC Volt meter probes (polarity does not matter if you use DMM) on the two legs of R9167 then turn on the TV while watching the meter and then wait 10 seconds to see what the Voltage changes to, repeat the same test on R9169.
https://www.shopjimmy.com/samsung-bn...-led-board.htm

[Diah]

Re: samsung ue55ju6800 problem with brightness

gamma chip problem... Maybe.

+10
from his photos the darkness straight its tell not LED issue
https://www.badcaps.net/forum/showpo...43&postcount=3

[nomoresonys]

Re: samsung ue55ju6800 problem with brightness

Ok, so do test in post 27, will it be another 2 weeks before your next post?

[R_J]

Re: samsung ue55ju6800 problem with brightness

I would say it is the top led srtring is bad, either bad connection from the horizontal led strip to the vertical distribution strip or intermitint led on the top strip.
You said the fault is intermintint, so try tapping the rear (metal) of the panel where the upper strip is attached.

[budwich]

Re: samsung ue55ju6800 problem with brightness

Your TV has two LED driver circuits, and two LED strings.
https://www.badcaps.net/forum/attach...4&d=1564065956
https://www.badcaps.net/forum/attach...7&d=1564065956
Do you see the two resistors (R9167, 9169) by the LED connector? As you can see, they are labeled for using as the test point, so with the TV turned off, keep the DC Volt meter probes (polarity does not matter if you use DMM) on the two legs of R9167 then turn on the TV while watching the meter and then wait 10 seconds to see what the Voltage changes to, repeat the same test on R9169.
https://www.shopjimmy.com/samsung-bn...-led-board.htm

I am having trouble understanding how this problem could be a backlight issue. You indicate that the panel has only two strings.... so "basic math" would indicate that half the screen would be in trouble. Yet look at the first pictures that the OP posted. It is at best 1/3 of a screen... maybe even 1/4. I don't see how that relates to one of two strings being in trouble.

[R_J]

Re: samsung ue55ju6800 problem with brightness

There are 18 strips in the panel (according to SJ) There are 2 connected together to form 1 horizontal strip. Each of the 9 strips are connected to 1 vertical connector strip. If one strip is going out it may not trigger an error to shut down the backlight.
I could be wrong but I don't see how any other board would cause this fault
It looks like one string is 4 strips (168v) and one string is 5 strips (210v)
The power supply lists (2D) 227v & 182v for each string
It should be easy to check the voltage across the string when it is working and not working

[budm]

Re: samsung ue55ju6800 problem with brightness

https://www.badcaps.net/forum/attach...5&d=1562666779
It looks like some of the LEDs are shorted out, especially at the top right corner you see dark section compared to the top left corner of the screen.
Checking the Voltage on the resistors will give us a clue but it may take another 2 weeks to find out from OP.
Most of the time they will arrange the LED strips in alternate rows, I.E. LED ROW 1, 3, and 5 may be driven by LED driver #1, row 2, 4, and 6 may be driven by LED driver #2.

[george_gpu]

Re: samsung ue55ju6800 problem with brightness

Thanks all for your answer
I measure 2 resistors monday morning and i tell you

[george_gpu]

Re: samsung ue55ju6800 problem with brightness

Good day
i measure dc voltage in 2 resistors , only r9169 has 0,0036 volt ( r 9167 no dc voltage)
i measure right this time the cnl802 connector ( from power supply to led bar connection in panel) i have 220 volt in 3 greys (+)

i notice 2 led bars up in monitor has low brigthtness

[george_gpu]

Re: samsung ue55ju6800 problem with brightness

See photo

[budm]

Re: samsung ue55ju6800 problem with brightness

Good day
i measure dc voltage in 2 resistors , only r9169 has 0,0036 volt ( r 9167 no dc voltage)
i measure right this time the cnl802 connector ( from power supply to led bar connection in panel) i have 220 volt in 3 greys (+)

i notice 2 led bars up in monitor has low brigthtness

1) R9169 is connected in series with LED string #2, R9167 is connected in series with LED string #1, you indicated 0V reading on R9167 which means there is no current flow through LED string #1.
2) You indicated all 3 grey wires (+) have 220V on each one, but if you look at the pin names of the LED connectors, there are only TWO + pins, 1+ (pin 9) and 2+ (pin 1). 1- is pin 13), 2- is pin 5.
So based on your measurement, are you 100% sure that your measurements are correct?
See attached picture.

[george_gpu]

Re: samsung ue55ju6800 problem with brightness

good day
i remove panel
i measure led bars
i have in 3 up bars many fault leds
can you send me the type (is :bn96-38486a) for order

[budm]

Re: samsung ue55ju6800 problem with brightness

good day
i remove panel
i measure led bars
i have in 3 up bars many fault leds
can you send me the type (is :bn96-38486a) for order

What do you mean "Can you send me the type (is :bn96-38486a) for order"? You cannot buy the set of the replacement LED strips?
BTW, can we see the pictures of the panel showing the LED strips?

[george_gpu]

Re: samsung ue55ju6800 problem with brightness

I have 40 burn leds