Samsung UN55D7000LFXZA top of backlight not working

[Jtroutt19]

Hey guys got this TV where it's dark along the very top. Image is still there when testing voltage on the backlight connectors the TV will power cycle upon touching L2+ showing 44v on all except for R1 and R2 and L1 and L2 which jump between 4v and 6v

Any Ideas on fixing this issue.

[dick_barton]

Re: Samsung UN55D7000LFXZA top of backlight not working

What voltage do you have between the two legs of C9110, C9201, C9310, C9410

[aaronwt6]

Re: Samsung UN55D7000LFXZA top of backlight not working

Based on my experience with this and similar models, my guess is your top LED strip has one or more failed LEDs on it. This is an edge lit set. The top strip is typically two pieces hooked in series.

[budm]

Re: Samsung UN55D7000LFXZA top of backlight not working

I look at the boards connections and this is what I see:
This power supply/LED driver board has:
4 Boost converter circuits
4 PWM Controlled MOSFET
4 Main LED strings:
R1+ is the Anode of the first LED string that has LED strips R1, R2, L2, L1 connected in series. L1 - is the Cathode return of this LED string.
R3+ is the Anode of the second LED string that has LED strips R3, R4, L4, L3 connected in series. L3 - is the Cathode return of this LED string.
R5+ is the Anode of the third LED string that has LED strips R5, R6, L6, L5 connected in series. L5 - is the Cathode return of this LED string.
R7+ is the Anode of the first LED string that has LED strips R7, R8, L8, L7 connected in series. L7 - is the Cathode return of this LED string.\

So turn the TV off and keep the meter black probe on the chassis, put red probe on R1+ then turn the TV on watch the meter to see how high it goes up to and then wait 5 seconds to see how low it goes down to. Turn the TV off and then move the red probe to L1 -, turn the TV on and see how high the Voltage goes up too and then wait 5 seconds to see how low it goes down to.

Repeat the same procedures for
R3+/L3-
R5+/L5-
R7+/L7-

Pictures provided by shopjimmy.
http://www.shopjimmy.com/samsung-bn4...pply-unit.htm#

[Jtroutt19]

Re: Samsung UN55D7000LFXZA top of backlight not working

OK here are the readings

R1 319v 286v
L1- 1v but this jumps around but not much over a volt
R3 180v 150v
L3- 19v 44v
R5 180v 150v
L5- 19v 44.5v
R7 180v 150v
L7- 19v 44.5v

[budm]

Re: Samsung UN55D7000LFXZA top of backlight not working

OK here are the readings

R1 319v 286v
L1- 1v but this jumps around but not much over a volt
R3 180v 150v
L3- 19v 44v
R5 180v 150v
L5- 19v 44.5v
R7 180v 150v
L7- 19v 44.5v

Well, the LED string that contains the R1 strip/R2 strip/L2 strip/L1 strip has open circuit.

[Jtroutt19]

Re: Samsung UN55D7000LFXZA top of backlight not working

May I ask how you came to that conclusion?

[Jtroutt19]

Re: Samsung UN55D7000LFXZA top of backlight not working

Well I have discovered that this tv has been taken apart before. All the stripped screws and such and then once I get he panel out of the thing I discover this and it is like this on both sides. Hopefully pads are intact and I can just repair it

[Jtroutt19]

Re: Samsung UN55D7000LFXZA top of backlight not working

OK so I have to find these little LEDS now. They have a number on them. I have searched it but no luck.

LZ2XNS031

is the imprint.

[dick_barton]

Re: Samsung UN55D7000LFXZA top of backlight not working

You don't say where you are based. Possibly available from Shopjimmy if you're in the USA

[Jtroutt19]

Re: Samsung UN55D7000LFXZA top of backlight not working

I am located in Indianapolis. I don't want to order brand new strips. Nothing wrong with the strip itself. I would like to find the individual LED's. just need 6 of em.

[budm]

Re: Samsung UN55D7000LFXZA top of backlight not working

May I ask how you came to that conclusion?

By looking at the Voltages readings you provided and have the understanding how the LED driver functions.

[Jtroutt19]

Re: Samsung UN55D7000LFXZA top of backlight not working

Would you have any suggestion on how to find those LED's other than going through mouser page by page? What is that package style even called?

[vinceroger69]

Re: Samsung UN55D7000LFXZA top of backlight not working

maybe something like this?
https://www.aliexpress.com/item/FOR-...124162c1&tpp=1