Samsung LE46B530P7WXXU confusing backlight

[stedmund08]

Hi All,

This is my first post here after spending hours searching around and reading as much as I can - there is a great wealth of knowledge on this site and it's kind of addicting!

Anyway, on to my problem. I have a 46" LCD Samsung tv (LE46B530P7WXXU) where the backlight will randomly turn off. Sometimes it can be running for hours or even days, other times a matter of minutes. One way I have figured out how to make it 'short out' is to adjust the backlight brightness up-and-down and it particularly seems to dislike it lower down - typically around level 2-3 is where it most commonly triggers the shut down.

I'm new tv repairs so please bear with me and apologies if I'm asking any stupid/obvious questions.

So far I've tested along the inverter board at each transformer and when the backlight shuts off, none of the inverters appear to 'spike' in voltage as one would expect. However, it's rather difficult to diagnose with the fault being so intermittent of course.

All the capacitors look to be fine too.

I will try and post some photos shortly - if you can suggest any that might help, please let me know and I'll try my best to get them.

Thanking you in advance for any suggestions!!!

Cheers,

James

[sordids999]

Re: Samsung LE46B530P7WXXU confusing backlight

Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

[ReeceyBurger123]

Re: Samsung LE46B530P7WXXU confusing backlight

Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

That should be your signature lol

[sordids999]

Re: Samsung LE46B530P7WXXU confusing backlight

good idea

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

As stated in the original text - I'm in the process of uploading pics, thanks for your input.

[ReeceyBurger123]

Re: Samsung LE46B530P7WXXU confusing backlight

good idea

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

Here are some photos - apologies that the cover is over the inverter board..

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

Rear of the power board - can't quite tell from the photos but the underside of the transformers looks a little burnt and the whole board seems to be covered in something a little sticky?

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

I'd like to find out how to test the transformers but I can't find a schematic anywhere using those part numbers... TMB9 TM0914C and the long one across the top/s 3324340025ef 3324340024ef

[budm]

Re: Samsung LE46B530P7WXXU confusing backlight

That long board connected to the lamp is not inverter board, that is the balancer board. You have power supply/inverter board combo.
You need to check the LD (Lamp detect) pin on the power supply board, normal condition will be about 11VDC, not normal will be below 10VDC which may mean one of the lamp did not stay conduct which makes sense when you turn the backlghts level too low for the bad lamp (bad lamp connection) to stay conduct, it will only take one bad lamp to make the circuit to go into protection mode. It can also be the high Voltage is too low for the lamps to stay conduct.

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

Haha instantly learning things, this site is great. Thanks budm - I'll be sure to check that tomorrow (the multimeter I have here is only good for Ohms as it's fried)

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

I can't see an 'LD' pin - would 'INV-ON' be the same thing? has two 13v pins next to it..

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

My bad... Found them - there are two?

[budm]

Re: Samsung LE46B530P7WXXU confusing backlight

My bad... Found them - there are two?

The two pins are tied together so you can measure either one of them with ref to the chassis GND.

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

So, I just checked the pins and I seem to be getting less than 1 volt - about 18-20 mv...

[budm]

Re: Samsung LE46B530P7WXXU confusing backlight

So, I just checked the pins and I seem to be getting less than 1 volt - about 18-20 mv...

You check it when TV is on? What you can do is to have the meter hook up to LD pin and the chassis GND when TV is off,
then turn on the TV and then you should see 11VDC or more and it should stay at that level with backligts on, if the backlights go off then you will see the Voltage drops below 10VDC.
Also check that you do have 12VDC on the 12V pin.
Your meter is set to DCV, right?
You said that the backlights randomly turn off, so right now you cannot get the backlights to stay on?

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

Hi - no I have the board out of the TV at the moment and had it plugged in. The light goes off randomly sometimes after an extended period and sometimes quickly.. I'll try putting it back together and checking with everything running - the back-light will still work with that plug off? (the one with the LD pins in it)

Meter is set to DC and had to be turned all the way down to 200m (perhaps as there was no load because the lamps weren't attached?)

[vinceroger69]

Re: Samsung LE46B530P7WXXU confusing backlight

maybe connect everything up on the tv so all leads connected etc then if you get your multi meter probe and push it down the side of one of the wires going to the ld pin (at the end of the wire going into the connector to the ld pin theres a metal sleve so as long as your meter probe is touching that it will give a reading)

[budm]

Re: Samsung LE46B530P7WXXU confusing backlight

'(perhaps as there was no load because the lamps weren't attached?)'
you have to have the lamps connected otherwise it will be in the safety shutdown mode, all other connections should also be in place..

[stedmund08]

Re: Samsung LE46B530P7WXXU confusing backlight

Ok, so, I've installed it back onto the TV - I get 12v (DC) at the 12v pin and next to nothing still at the LD pins - even when light comes on for a moment, no spike etc. Obviously it wont stay on for longer than a second or so with the plug off but in the second the backlight is on I don't see any increase in voltage.

Thanks for your help so far - it's greatly appreciated... Any further suggestions greatly received