Category Archives: TV Repair

RCA RLED4250A No Backlight

This TV had no backlight but would turn on and off. Opening up the back, the power supply HTX-PI420402A had four pairs of wires going to the LED strips. I powered one pair with my LED tester and could observe the splash screen and confirmed that video was good.

I decided to open up the TV to check the strips and this edge lit TV used four sets – one at each side and two along an edge. All strips tested fine with my LED tester.

Shopjimmy sells a repair kit which includes two ICs and two FETs to repair the backlight circuit. I checked the FETs and diodes and none were shorted. Searching the power supply part number on badcaps, there was a suggestion to check the transformer for cold solder joints.

I found a cold joint and there were some clues if I had inspected the board more carefully. There was a scorch mark above the joint on the top of the PCB. The bottom of the PCB had an insulator sheet that had a hole at the cold joint location. And there was a crackling noise coming from the board occasionally, caused by the joint arcing.

Though 90% of no backlight cases are caused by bad LEDs, in this case it was the power supply.

Other models that may use this power supply –
Haier LE42B1380
Haier LE55B1381
Viore LED42VF80
Seiki SE421TT
Seiki LE-55GB2
Curtis LED4250A

Panasonic TC-60CX650U Backlights Flash 1 Blink Code

When turned on, the backlights flash and the front led flashes a one blink code. According to the service manual that can be found online, it is a backlight error.

I recorded a video of the flash and from a still frame, the third row was not lighting up. The left and right strips did not come on and I found two bad LEDs on the left strip. The right strip tested fine. This TV has local dimming and though left and right strips are wired separately, they are dimmed row by row. I used Samsung 3V LEDs and the color was a bit off and they were a bit brighter.

I decided to take apart the TV a second time to move the repaired strip to the bottom of the TV and also remove a fleck of dirt trapped under the panel. Unfortunately, I cracked the panel after putting pressure on the edge when I missed a screw in the bezel. In hindsight, I should have removed the bezel completely with the TV lying flat.

For the record, part number for the strips are as follows
Left CX-60S02E01-3B5Y3-0-B-523-1208-U
Right CX-60S02E02-3B5Y3-0-B-523-1297-U

Samsung UN50ES6820F Backlight but No Video

UN50ES6820 UN50ES6820F UN50ES6820FXZC

This TV turned on with backlight but no video. Usual suspect in this case is the tcon board though a bad main board could also cause no video. If I had sound, it would strengthen the case for the main board to be good.

The model appeared to be Canada only and there was a lot of variation in the model numbers for the ES series. Tcon part number was 35-D076725 and main board was BN94-05874R (BN97-06430L firmware).

Replacing the tcon brought the video back. I did notice the volume had been lowered to 0 which was the reason there was no sound. In this model, there is a sound effect if you scroll through the menu.

This model does have backlight issues so make sure they aren’t set to maximum or the picture mode set to Dynamic.

RCA RTU6049 No Video

Backlight failure is common in most RCA models mainly because the backlight is set in the service menu. On some models, there is a Power Save picture mode which lowers the backlight but Standard and Dynamic modes typically run the backlights at 100%.

In this two year old TV, the backlights would shut off after a few seconds or minutes but would stay on for a few hours when the level was reduced but it still cut out.

Opening the TV was a bit of a challenge since the panel was taped to the bezel. There were also screws hidden under the thick foam spacers supporting the panel boards. I realized afterwards that the tv had to be assembled with the diffuser sheets and panel face down inside the bezel and the chassis should be lifted away.

Once the tv was apart, I tested all the strips with my LED tester and they all appeared good. They were probably only failing under higher current. Since I couldn’t isolate individual bad LEDs, I decided to do a full strip replacement.

There appear to be at least two different panels for this model. I initially ordered the wrong strips since I didn’t want to open up the TV again to check the part number. JL.D60081235-031AS-M (AE110475) are 12 half length strips with 8 LEDs per strip. My strips were SQY60LB (AE0110384 or AE0110383 ) which are six rows of left and right strips (8 leds per strip). Shopjimmy indicates these are used in model RLED6090.

When I put the TV back together with the new strips installed, there were some moving lines which I eventually traced to a poorly grounded tcon. I had removed the tcon to release the tabs of a standoff to lift off the reflector sheet.

The service menu for this model is accessed by SOURCE-2-5-8-0 and reducing the backlight saves it under User picture mode. It is recommended to keep the picture mode as Power Save to prevent backlight failure.

Update: After I sold the tv, the new owner inquired about turning off motion smoothing since it creates the soap opera effect when watching movies. Some models have a 120Hz or MEMC (Motion Enhancement Motion Compensation) setting in the Picture menu. Working with him, we were able to find a Film Mode in the Service Menu and turned that option on.

UN58H5202AF Flashing Backlight No Video

UN58H5202 UN58H5202AF UN58H5202AFZXC UN58H5202AFZXA

This model suffers from backlight failure that pops a transistor on the power supply leaving the tv dead. See post here. This tv had different symptoms with a flashing backlight and no video.

I opened up the tv and the majority of leds had burned out so I replaced them with used strips I had salvaged. With the main board unplugged, the backlights came on. With the main board plugged back in, but panel still disconnected, the tv went through the normal start up processs when turned on. I reassembled the tv and it still did not display a picture. Suspecting a bad panel, I was able to get a picture with only the right side tcon cable connected indicating a fault on the left side of the panel. I checked the left side panel board for shorted chip caps but didnt find any. Next, I tried blocking some of the left side tcon flex cable with tape (“tape cutoff method”) but that didnt work either. As a last resort, I ripped off all the side tabs on the left side of the panel and was able to get a good picture.

I’ve only done this once before on a Sharp 60 inch tv but it only lasted a month or two before the panel had other issues.

Sony KDL-55EX620 Dead 10 Blinks

I previously repaired this model with 2 blinks by replacing some mosfets here. This one appeared dead with no standby light and it didn’t turn on. A service manual and service/training manual can be found online. Checking for standby voltage, both 12V and 3.3V were present on the main board. I also checked all the fuses and regulators and they all were good.

Searching the main board part number, I ordered one from an online tv parts supplier. When Sony main boards are replaced, the firmware needs to be updated.

Downloading the firmware from Sony’s website, I extracted the file and subfolder onto the root of a FAT32 formatted USB drive. I did have some trouble getting the firmware to update but what worked for me was turning the TV on which flashed green and amber. I then plugged the USB in and after a few minutes if flashed red and amber. Instead of rebooting, it blinked an error code. With the USB unplugged, and the tv turned on again, the tv flashed on for a second before giving me a 10 blink error code. I tried going in to the service menu, but couldn’t because of the error.

The service manual had no listing for a 10 blink code so I was stuck. I suspected that the main board had to be configured for my panel so purchased another main board from a KDL-55EX720 which uses the same panel. This model is 3D and has a higher maximum refresh rate.

When I installed the second board, the tv flashed the same 10 blink code but I didn’t need to update the firmware. Looking at the service manual for the KDL-55EX720, it had an entry for the 10 blink code – Emitter Error. The flowchart indicates to check the HEM2 board. Looking for the HEM2 board on my TV, I didn’t have one. The HEM2 board is for mounting IR LED emitters connected to the tcon used to sync with active 3D glasses. The schematic for the HEM2 board shows an EMI_FAIL pin which I assumed would trigger the 10 blink error. It is either open collector or at ground.

I ordered a HEM2 board with cable from ebay but decided to see if I could get the tv to turn on by grounding EMI_FAIL (pin 7) on the tcon board. I had to ground it before plugging in and kept on grounding it to prevent the 10 blink code from reappearing.

Multiple versions of the Sony model use the same main board and firmware. So it appears if the main board was configured for a 3D one, it will be checking for the EMI_FAIL signal and produce a 10 blink error if the board is not installed.

Most board sellers group all the boards together since they have the same part number so you will encounter this issue if the board is configured for a 3D TV and you are trying to install in an non 3D model.

Toshiba 58L1350U Backlights Flash

Canadian model number is 58L1350UC. Power supply part number is PK101W0220I.

I had previously repaired this model with a shorted power supply transistor here. On this tv, the backlights would flash on power up which is a sign of bad backlights. I ordered a full set of backlights since the owner said it had been previously repaired and it may have been run at maximum backlight level.

With the TV opened up, I found one out of five strings with multiple led failures. I replaced all the strips anyways. With the new strips installed and the tv plugged in but off, the string with the previous failed leds glowed. When turned on, the backlights did not come on.

Checking the LED controller circuit on the power supply board, it appeared each strip was individually powered and controlled. I checked all the transistors in the circuit and they all appeared good. I suspected the bad LEDs damaged the LED controller IC OZ9908BGN. I was able to find a replacement on Aliexpress.

Once the part came in, I did have a lot of issues soldering the IC since the part was probably old and there was poor solderability on the pins. With each pin tested for continuity, I finally got the TV to power up with all the backlights staying on.

Samsung LN40B500P3F Backlights Flash

Model LN40B500 LN40B500P3F LN40B500P3FXZA

When turned on, the backlight would come on for a second, turn off and this would repeat for a couple of times. Power supply part number is BN44-00264A. Schematic is available online. This badcaps thread indicates potentially bad transfomers on the inverter or bad ccfl bulbs in the backlight. I hooked probes to the main filter cap to monitor the PFC voltage and it was steady around 390VDC throughout. The thread indicates to connect a wire to pin 10 of the UI801 to see if the overvoltage protection was being triggered from faulty bulbs. This signal was high when the backlights were on confirming the fault. The thread also mention to bypass CI805 on pin 2 which should keep the backlight from shutting off. This modification worked as well. I put a plain white image on the screen and could verify a few bulbs were dim and triggering a fault.

Since the LCD TVs are becoming old and obsolete, I decided to scrap the TV and was able to use the main board on a LN46B500 TV I had.

Samsung LN46B500P3F Doesn’t Turn On

Model LN46B500 LN46B500P3F LN46B500P3FXZA

This TV had a standby light but didn’t turn on. With the main cable unplugged from the power supply, the backlights turned on. The main suspect in this scenario is the main board. Searching for the part BN94-02746Z on ebay yielded some expensive boards and an eeprom from Shopjimmy. I tried freezing the eeprom but the TV didn’t start but I bought a new eeprom anyway. After installation, it still didn’t work. Shopjimmy indicated BN94-02746L was a substitute part but I couldn’t find either at a reasonable price. Searching without a suffix showed BN94-02746Y from LN40B500 may work since the board picture matched but again there weren’t any reasonably priced boards on ebay.

Putting the TV aside, I was able to get a LN40B500P3F with backlight issues and a BN94-02746Y main board. Plugging it into the 46 inch model worked. A second LN40B500 substitute is BN94-02746K.

I proactively replaced four electrolytic capacitors on the power supply board BN44-00265A.

CM858, CM859 – 1000uF/25V
CM852, CM853 – 1000uF/10V

Haier 55UFC2500 No Picture

This TV turned on with no backlight. Google indicates this model suffers from backlight failures but replacement LED strips are not readily available. This set is configured as two strings of LEDs and one open LED was found. It was repaired with a 3V Samsung compatible LED module.

Backlight level can only be adjusted in the service menu under Panel Settings. With the tv on, menu-1-1-4-7. Vivid mode sets the backlight to 100%, Standard is 85%, and Energy Saving 50%. You should keep the TV in Energy Saving mode or adjust Standard mode to 65% which gets saved as User mode. You will need to make this adjustment for all inputs.