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Turn Down Your Backlight Level in Roku TVs

LED backlight failure is common in all LED TVs. With Sharp and RCA Roku TVs, turning down the backlight level isn’t very intuitive.

  1. Under Settings-> TV Picture Settings Set the TV Brightness to Normal. It defaults to Brightest I’m not sure if this is controlling image brightness or backlight level but safer to set it to Normal.
  2. With your current input selected (eg HDMI 1), hit * on the remote. Go to Advanced Picture Settings. Set Picture Mode to Low Power, Dynamic Contrast to Off and the Backlight to 60-70. The lower you can tolerate the better. The default for low power is 78 which still seems high. Most picture modes set the backlight at max which will burn out the LEDs.
  3. Repeat step 2 for all inputs you are using and also check all apps (eg. Netflix, Roku media player you are running.

Samsung UN40EH and UN40H LED Backlight Strips

I was doing a led replacement for a UN40H6203AF and ordered replacement strips, but the middle strip didn’t match. These series of Samsung LED TV’s use 3 strips with 2 angled strips and a middle straight strip. Part number is LM41-00001V for the angled ones and LM41-00001W for the straight one. When I installed the straight strip, the holes didn’t match. I noticed there were 12 leds on the strip and I needed 13. Though the angled strips were the same part number, the straight strip was different.

For the 13 led straight strip, the part number is D3GE-400-SMB-R3

LG 32LC7D Slow to Turn On

I don’t see a lot of LCD TVs anymore since they are getting old and obsolete. This one had almost all the 2200uF/10V capacitors bulged. I proactively replaced the 470uF ones as well.

C221, C206, C217, C202, C215 – 2200uF/10V
C222, C226 – 470uF/25V
C203 – 2200uF/25V
C210 – 1500uF/35V

Update: I encountered another 32LC7D with one bulged cap but the backlight did not come on. Backlight control comes from the pin labelled I-C and there was no high signal from the main board so I replaced the board. The capacitors on this board were also replaced.

C207 – 1000uF/35V
C212 – 2200uF/25V
C203, C208 – 470uF/35V (one is actually 25V)
C215, C225 – 2200uF/10V
C204, C205 – 3300uF/10V
C221, C222, C223, C232 – 680uF/35V

LG 49UJ6500-UB Blue Purple Tint

This 2 year old TV had a blue and purple tint and the backlights were suspected of turning blue. Removing the panel confirmed this colour change happened. Shopjimmy only shows one set of backlights for this model but they didn’t match what was in my tv. Shopjimmy part is 3 rows of left and right strips with 9 LEDs per row and labelled 49UJ65 for panel HC490DGG-ABSR2. My TV has a LC490DGG panel and strips are marked V17 ART3 and there are two rows of 12 LEDs per row.

Update: Seen same issue on 43UJ6300-UA with 3 rows of long strips. They have the same large flat lens.

Update 2: Sony XBR-49X700D appears to use the same style backlights and suffer the same problem.

Update: I popped off the lens to investigate and it appears these LEDs are naturally blue but are covered in a yellow filter. The yellow filter has cracked and crumbled away.

Blue LED Closeup

UN65MU6290 No Backlight

UN65MU6290VXZA UN65MU6290VXZC

I researched this model thinking I could repair it since I had salvaged parts from a cracked screen TV. Apparently, there are two different versions. UN65MU6290F and UN65MU6290V. The V version is edge lit and is very prone to backlight failure. Shopjimmy recommends replacing two resistors to limit the backlight current after LED replacement. This ebay post from a backlight seller indicates bad LEDs can damage the power supply and bad power supplies can damage the LEDs.

“On this model most of time one led strip and power board fail at the same time, to fix this issue you must replace that failed led strip plus power board. If you install this LED strip with failed power board and turn the TV on, LED strip will fail on the spot, also if you install a good power board with bad LED strips the same thing would happen to that power board. “

This ebay listing indicates the LED driver IC IC9101 SEM4082A can fail as well as Q101c and Q201c.

On top of all these potential issues, the back cover is screwless and needs to be pried apart. There are holes at the bottom to insert a tool to start prying apart.

LG 32LK450-UB No Backlight

This LCD tv turned on but without a backlight. Googling found a repair kit for transistors on the inverter board.

Testing the transistors on the inverter board, I found Q103 (Nikos P4004ED PCH, 40V, 21A) shorted and F101 (240V, 7A) blown. Replacing both parts restored the backlight. If Q105 or Q107 are shorted, the part is P2904BD (NCH, 40V, 25A).

Samsung UN55F7050 Won’t Turn On

Model UN55F7050 UN55F7050 AF UN55F7050AFXZC

This model appears to be a Costco Canada version of UN55F7100 UN55F7100AF. When the power button is pressed, the front LED blinks but the tv doesn’t turn on and there is no backlight. Disconnecting the cable between the main board and power supply, the backlights came on indicating the power supply and backlights were good but the main board was suspect. I sent the board to a repair service on ebay and they indicated the board was good. When I got the board back, I tried powering up the tv with one of the ribbon cables between the tcon and panel disconnected and the tv powered up with one side disconnected. This result indicates there is probably a short on the panel. I did measure low resistance between capacitors on the panel board on the bad side but it would have been extremely difficult to trace a shorted capacitor. I also tried blocking some ribbon connector pins with tape and also removed the side tabs but the tv was a lost cause.

Update: It was likely there were shorted caps on the panel board. I should have had the patience to remove and test every one that appeared shorted.

LG 60LN5600 LED Backlight Replacement

LG’s LN series comes in a variety of sizes and variations but they all seem to suffer from LED backlight failure. I did a LED replacement of a 60LN5600 which used the thick style lens but replacement was difficult due to the reflector sheet being glued down to the chassis. It was difficult to remove without stretching or ripping it and I had to tape it back down after I replaced the strips. Some of the new replacement lenses were loose and I had to reglue them back on after they were knocked off.

RCA RTRU5528 No Backlight

RTRU5528 is the Canadian model and RTRU5527 is the US model.

This tv was reported as having no backlights. Opening up the panel, the backlights tested good with an LED tester. There was a standby light and the tv turned on but without backlight. I then noticed a blown up MOSFET on the power supply board. Some components on the back side were also damaged. Checking other components, D401 was shorted as well. I would recommend checking D401 – D404 and checking the main fuse F101. Power supply part number is HSL55D-2S9.

Here is a list of parts replaced
Q506 & Q507 TF5N50 (NCH 500V 5A) Digikey FDPF8N50NZ-ND (8A substitute)
Q504 & Q505 (2T marking) MMBT4403 (PNP 40V 0.6A) Digikey MMBT4403LT1GOSCT-ND
D509 (T4 marking) 1N418 100V 0.3A Digikey 1N4148W-FDICT-ND
R506 240 ohm 1206 Digikey 311-240FRCT-ND
R533 & R528 30 ohm 1206 Digikey 311-30.0FRCT-ND
D401 SF26 400V 2A Digikey 1655-1581-1-ND
F101 4A 250V fuse Digikey 507-1721-1-ND

LG LN Series Bad LED Backlights

I have repaired dozens of LG LN series TVs with bad LED backlights. Symptom is the LG logo flashing on power up and the TV is on with sound but no video because the backlight has shut down. Though a LED tester will confirm the failure, it is possible to confirm bad LEDs without one but you need to remove the panel to watch the LEDs flash.

LG Logo Flash on Power Up LG 42LN5700 (looping)

The flash is caused by protection circuitry shutting down the backlights because an error is detected in the LED driver circuitry. Driver circuits are current sources driving the leds wired in a series string like Christmas lights. LEDs can fail short (most common) which will cause an undervoltage situation. If LEDs fail open, there will be overvoltage that the driver can detect as well. If there is an open LED, the backlights in that string will not flash. In non-smart LG models, there is no logo and there may just be a quick backlight flash.

The shutdown protects the rest of the LEDs and the power supply. It may also prevent the LEDs from burning up. I have seen LEDs burn up in LN series even with the protection shutdown.

There are a lot of youtube videos on panel removal and I will include one here from Shopjimmy. The panel is extremely fragile and you need to be extremely careful to not crack it. The boards flex connected to the panel can also be ripped off very easily. Damage to the panel or those boards is not repairable.

The TV will turn on with the panel disconnected so you can observe the flashing. By going frame by frame, I took a capture of the flash where you can see two LEDs not lighting up. If you have an LED tester, disconnect the strips from the power supply and probe each strip individually.

LED backlight flash with the panel removed LG 42LN5700 (looping)
Capture of flash where you can see two LEDS not lighting up

LEDs are likely to fail if the backlight level is set to maximum. They get hot and will burn out over time. Failure could occur between 2-5 yrs. On LGs, the default picture modes for Standard and Vivid modes are at 100% level. With the LN smart versions, apps may also default to 100% backlight and can only be changed in the Quick menu.

Repair Options

  1. Full replacement of all strips with NEW ones. This option is preferred to minimize future problems with your backlights. Reputable sellers include Shopjimmy and ebay seller meihua361000 based in China. I have had failures with Rzconne branded strips so best to avoid those.
  2. Replace bad strips with used ones. This option is cheaper if you have used strips but if you are buying strips, its only a bit more for new ones. Because there is wear on the existing LEDs, they may fail in the future.
  3. Replace the LED itself. The LEDs are pretty cheap but you could have an issue with centering the lens back on. If not perfect, it can cause bright spots. For the LN series, you can find 3V 2835 LG replacements on Aliexpress. https://techhometravel.com/lg-42ln5700-logo-flashes-no-picture-has-sound/

It is preferred to have your replacement strips in hand before doing the repair. If your tv has been disassembled for weeks waiting for parts, you may forget how it goes together. You also risk damaging the LCD panel if you haven’t stored it safely and prevented it from gathering dust. However, some models use different panels so may have different strips even for the exact same model number.

To ensure your repair lasts, you need to turn down the backlight level. This setting is in the picture menu. For LGs, 50 to 70% is recommended. With apps, you need to access the Q.Menu to adjust the backlight level. You need to do check on ALL inputs and ALL apps. I would also recommend turning Energy Saving OFF since this could increase the backlight level in a bright room.

Samsung TVs

Samsung TVs also have LED failure but they don’t have shutdown protection. LEDs will fail until there is damage to the power supply or the screen will get very dim. With Samsung TVs, you can disconnect the cable from the main board to the power supply and this will force the backlights on for testing.

You can also set the backlight level on Samsung TVs. Dynamic picture mode will crank the backlights to 100% (level 20/20). It is recommended to set the backlight level between 10-14 to make them last.

Burnt out backlights UN58H5202AF causing failure of Q9101 FET on the power supply

RCA/Proscan/Haier TVs

These models have a protection feature but there is no backlight setting in the menu. However you can turn it down in the service menu under Panel Settings. With the TV on, try Input-1-1-4-7 or Source-2-5-8-0 Be very careful with service menu settings since you can brick your tv. I would check every input and set the backlight to around 60. Some models will have an Energy Saving picture mode which runs the backlights at a lower level.

List of backlight repaired models

LG 32LB5600 42LN5200 42LN5700 42LN5750 47LN5700 47LN5750 50LA6205 50LB6100 50LB6500 50LN5310 50LN5400 50LN5700 50LN5750 55LB5800 55LB6100 55LF6000

Vizio E60-C3

Samsung UN40EH5000F UN40EH5300F UN40H5203AF UN46H5203AF UN46EH5000F UN46EH5300F UN50EH5300F UN55D6300SF UN55FH6030 UN55ES6100F UN58H5202AF UN60ES8000F

Haier 40D3505 55UFC2500 65E3550

Insignia NS-37D20SNA14 NS-55D550NA15

RCA/Proscan RTU5540-D RLDED5078A-D RLDEDV3988-A EP5585 SRC5565 RTRU6049