Blaupunkt 23/157I-GB-3B-HBKDU

[randomf]

Hello,

I have faulty 23" Blaupunkt TV with dead LED backlight. I've opened the TV, it has Samsung LTA230AN01 HD Ready panel with single 33 SMD LED stripe on a side. I've tested each LED with a multimeter and they all lit up.

According to panelook.com the voltage coming to the LED stripe should be 33V but I can measure only 11.7V coming out of a power supply without load. The power supply has label 81-PBE0241-PW11 rev 0.2 (see pictures included). The caps looks ok from the outside. Does anyone has experience with this panel can he / she confirm the required voltage? Any other suggestions?

Thank you

[randomf]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

So I have unscrewed the PSU and removed the covering plastic. The board itself revealed from the bottom LKP-PL034 rev 0.2. However I can't find a schematics online so I can't find out if the output voltage is correct or not

[Andrew F. Ali]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Without a load the LED Backlight power supply will power down...so that 11.7V may be the power down voltage to protect the power supply on open circuit. From the 1st picture you have open LED/s on the strips. Replacing the LED strips will solve your issue.

[ReeceyBurger123]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Led voltage will be about 80v or so maybe lower, also how are you testing the Leds ?

[randomf]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Led voltage will be about 80v or so maybe lower, also how are you testing the Leds ?

I use LED tester function on the multi meter and touch each LED with probes (they all light up)

[Andrew F. Ali]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Your 1st picture shows the three LEDs alone lighting up....suggesting to me that all your LEDs are not working..........or is that a reflection from your camera flash?

[randomf]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Your 1st picture shows the three LEDs alone lighting up....suggesting to me that all your LEDs are not working..........or is that a reflection from your camera flash?

Sorry that picture is misleading. Its caused by my torch. No LED is lighted up on that picture.

[dick_barton]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Your power supply board may have the led voltage written on it. If you disconnect the leds and switch on and see what the voltage at the leds jumps to before falling back.

[vinceroger69]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

can you add a picture showing the bottom of the power suppy it may have some ics on etc that may run the leds whats under the aluminium cover on the left of the power supply

[randomf]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

I can safely rule out that the LED strip is ok. I bought 4 9V batteries, plugged them in series and sent the output to the Molex connector on the screen. As expected, they all lit up. There are 3 parallel segments per 11 LEDs, I'm looking for ~ 35V.

Back side of the PSU is attached

[randomf]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Under the heatsink closer to the LED connector is MBR20100CT.

[randomf]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

So I have unsoldered nearly all parts apart from the SMD IO (OB3370N) on the LED part of the power supply, measured them with ESR meter, they were all good so I soldered them back to measure signals from the controller and everything started to work. So I guess cold joint.

[vinceroger69]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Hopefully you have found the faullt and as you say was a bad solder joint all you can do now really is use it for a few days turning it on and off a few times then hopefully the fault wont come back and you can call it fixed.

[randomf]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Unfortunately the story doesn't have happy end. The problem got back. I can't measure power on signal from the main board so I'm searching for a problem.

[trutle]

Re: Blaupunkt 23/157I-GB-3B-HBKDU

Hi,
I have a tv of the same model that needs the eeprom 25Q32 bin file? Can you read yours and send it to me? I can then help you troubleshooting your problem.
Thanks.