Re: Samsung backlight issue

Thanks very much for your help!

Is it worth trying to source replacement CCFLs? Are there any good suppliers in the UK? Or should I just accept that after 10 years it is probably time to get a new TV set?

Re: Samsung backlight issue

OK, so pin 12 of UI801 is 0v.

I'm trying to think what is supposed to bring the voltage up, and wondered if it is ON_OFF. I decided to try checking PC803S, and this is 0v apart from pin 4 which is 5.22v

Then I checked round ub802 to chase INV_UVL0, and all pins are 0v. I have a strong feeling I am barking up the wrong tree here though.

Re: Samsung backlight issue



Thanks again.

Looking at the schematic, I think I need to measure to S-GND which is the chassis? This chip is on the solder side, so I needed to unplug the board from the backlight connectors and flip it over to access the chip. It is still connected to the mainboard. I believe the dot is next to pin 1, so pin 16 is opposite pin 1. Voltage to chassis is 9.7v. I also checked to pin 6, again 9.7v.

Voltage to P-GND is 0v, but if I understand correctly these circuits are isolated so that is meaningless....

Re: Samsung backlight issue



OK, Thanks for your patience!

BD901 - 340v

All pins on QI821 are 0v. I don't understand how this fits in with my measurements yesterday, but I checked a number of times....

Re: Samsung backlight issue



Thank you for your help.

BD901 is at 116v DC to ground, which isn't what you expected. Does this mean the problem is before the inverter?. QI821, I am not sure which is the drain pin, so with the writing facing me, and working left to right, I have (Again measuring in DC):
[LIST][*]-117.5[*]117.5[*]-118.2[/LIST]

I did [URL="https://elektrotanya.com/samsung_bn44-00259a.pdf/download.html#dl"]download the schematic[/URL] but don't really know enough to understand it properly.

• Re: Samsung backlight

...

Re: Samsung backlight issue



Not so far as I can see.



I believe I did this, though on the mainboard end of the cable, because it is difficult to get to the pins on the power board side. The measurements are left to right, and the labels are in the picture. I will reformat them below in the hope that helps.

[CODE]
Pin Voltage on Voltage Standby
NC 0 0
DET_5V 0.29 0
E-PWM 2.18 0
Inv_ON/OFF 5.13 0
13V(M) 13.03 0
13V(M) 13.03 0
GND 0 ...

I have a Samsung TV, model LE26B450C4W. I believe it is a backlight issue because I have tried shining a light at the display and could see a picture when it was all connected up. I can't see the menu now I have disconnected it, but maybe that is because I am not getting the right angle. The LED on the remote sensor behaves as I would expect though.

The issue was intermittent for a while, the TV would either work or not but now it seems fairly consistently dead. I measured the resistance of the secondary windings of the inverters, and found the following resistances:
...

Re: New Members - please post your introductions here

Hello! I am joining because I want to try to mend my TV. I studied electrical and electronic engineering at University, but then went into IT, so I have no real practical experience.