Hi everyone thanks for accepting me to your forum. I have a problem with the above set, functions perfectly apart from backlights. I've tested them with LED tester and both sets light up ok in fact with the tester connected the TV is perfectly watchable. When connected to the BN44-0876A supply they don't illuminate, I've removed the connection to the main board which I believe should have brought them on as well but nothing. Is it possible for the fault sensing in the power supply to pick something up in the LEDs which the tester isn't showing or is it more likely to be a fault in the PSU?
-
-
Re: Samsung 49KU6400U backlight
You need to get a multimeter and do some measurements.
Also, with LED tester, are all LED's on? No dark spots? What are voltage readings with LED tester? -
Re: Samsung 49KU6400U backlight
Light spread looks ok no dark spots (it's edge lit) I'm showing 72 volts on each array (there's 2). Refering to the picture I'm measuring with LEDs connected:
Pin 3 1+ 365v
Pin 7 1- 296v
Pin 4 2+ 296v
Pin 8 2- 227v
All measurements to case.Attached FilesComment
-
-
Re: Samsung 49KU6400U backlight
Did you measure it with multimeter or LED tester?
If with LED tester, you should unplug connector and measure at connector pins.Comment
-
Re: Samsung 49KU6400U backlight
The BN44-0876A appears to be a power supply for a 55" set with led voltage when in 2D is given as 200V @520mA and when in 3D given as 231V @ 1040mA
Is this the correct power supply for your set?
https://www.shopjimmy.com/samsung-bn...w-112345157940Willing to help but I'm no expert.Comment
-
Re: Samsung 49KU6400U backlight
Yes mate that's the one. I believe it's fitted to quite a few different setsLast edited by russianbar; 05-25-2021, 09:39 AM.Comment
-
Re: Samsung 49KU6400U backlight
Supply voltage to LEDs looks OK.
There is a mosfet that controls current through LEDs.
It's drain should be connected to pin 8 of connector.
Check the voltages on that mosfet pins.
And obviously inspect PCB for solder joint cracks, check transistors and diodes with multimeter.Comment
-
Re: Samsung 49KU6400U backlight
All looks ok apart from what looks like a choke/coil inductor which is open circuit L9101CS?Attached FilesComment
-
-
Re: Samsung 49KU6400U backlight
Run some fresh solder on the inductor pads and test again. L is generally a prefix for an inductor.Willing to help but I'm no expert.Comment
-
Re: Samsung 49KU6400U backlight
Took it out still o/c but big crack in the base looks like we may have the culprit, anyone know of an equivalent because the number doesn't bring up many resultsAttached FilesComment
-
-
Re: Samsung 49KU6400U backlight
I found this part reported bad in other forums, so it seems to be typical failure.
And I found datasheet too:
http://www.mu-sem.com/bbs/download.p...&wr_id=14&no=0
3mH is quite high value for inductor.
You can search replacement by inductance and other specs in the datasheet.
Or if you have a meter with inductance measurement, you can try some parts from scrap boards like transformers, common mode chokes. And you can connect windings in series to get the right inductance. It doesn't need to be precise, can be 20-30% off, usually slightly more is better.
Good luck!Last edited by alfatv; 05-26-2021, 02:02 PM.Comment
-
Comment
-
Re: Samsung 49KU6400U backlight
In your language, but not much useful
https://kenotrontv.ru/topic/7464-sam...ont-podsvetki/
https://kenotrontv.ru/topic/7455-isc...p-bn44-00876a/
http://monitor.espec.ws/section48/topic320937.htmlComment
-
Re: Samsung 49KU6400U backlight
New power supply board from Ebay £10 and sorted. Not impressed with picture on the set though (given to me by daughter fix and keep) it'll be ok for a bedroom I suppose. Menus and guides are razor sharp but the definition even UHD below par. My main set is Sony KD-55X8509C am I expecting to much from the Samsung in comparison. Anyone know if there is any adjustments needed to match supply with set? Might swap the good inductor out of the new board and put it in the original?Comment
-
Re: Samsung 49KU6400U backlight
This is a entry level tv and not one of Samsung’s best. I believe it’s only 60hz refresh rate. The ku9500 is probably closer to your Sony.Comment
-
Re: Samsung 49KU6400U backlight
Massive thanks to all contributors
Comment
)
-
This specification for the Samsung Galaxy Book 2 Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the Galaxy Book 2 boardview and Galaxy Book 2 schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from our users directly on the relevant badcaps forum. Please note that we offer no warranties that any specification, datasheet, or download...09-07-2024, 05:50 AM
-
Samsung LN46C630K1F – Intermittent Backlight, BN44-00341B Power Board
Summary for TL-DR readers:
• Backlight is intermittent, may come on with TV boot or not. No flickering, never fails during TV on.
• Have obtained Samsung schematic & service documents - Can upload if helpful.
• Have read ALL applicable threads
• C1818 and CP820 replaced as low hanging fruit
• CN802 data taken for normal and failed BL operation. SUMMARY: Pin 2 - 5vDet = 3.52 @normal, 0.0 @BL fail. Pin 6 - EPWM = 1.631 @normal, 1.058 @BL fail.
• VCC pin (18) of PFC... -
this tv is throwing me for a loop. do samsung tvs no longer have the backlight self test feature built into the power supply?
i tested the backlight with my LED tester and it lights up both strips. one of them reads 100v and the other reads 63.7v.
unplugged mainboard from power supply but left backlight plugged in, and then plugged psu wall power in. expected to see backlights light up but see nothing.
according to how ive diagnosed in the past, this would almost always be a bad power supply. replacement power supply was cheap like 20$ from ebay. but still i get not even... -
Hi everyone!
Hope you're all having a great day, and thank you very much for stopping by and taking the time to read this post to help me with my parents' Samsung TV.
My issue: No backlight.
Model: QE82Q70RAT
Type No: QE82Q70RAT
The TV was already serviced by Samsung once under warranty for the exact same issue, but six months after the fix, the backlight went out again. Now, Samsung is asking for nearly the same price as a brand new TV to fix this with the same 6-month guarantee.
So hopefully, I can fix this cheaper.
... -
TCL 75S421
PSU BOARD: 40-L402H8-PWD1CG
it shows not even a flash of backlight when powering up.
but the tv appeas to turn on and i can hear the sound of the menus moving and clicking. i can power down the tv with the button.
testing the backlights with my tester all 4 strings lit up and showed similar voltage drops. around 110 or so.
unplug mb and leave only psu plugged into backlights (PSU + BL SELF TEST MODE?) does not light the backlights.
i do see 24v but 0v on PSON and BLON (i didnt write this down tho so cant be sure)
with mb connected, PSON...
Comment