Saumsung le40b554m2w; Sound but no picture

[donst]

Hi all,

I have a samsung le40b554m2w that is around 3-4 years old now that is having problems and i just hoping that someone here can help me out.

Basically, i am getting sound but no picture. When initially turning the tv on the picture shows up for about half a second and then the picture just goes black/blank. Does anyone know what the problem could be and how i can go about fixing the problem?

Thanks all, all help much appreciated.

[budm]

Re: Saumsung le40b554m2w; Sound but no picture

You can start by posting good clear pictures of the back of the TV and the boards.

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

Hi, sorry about that.

http://oi41.tinypic.com/358c9hh.jpg

http://oi39.tinypic.com/2dcj380.jpg

http://oi39.tinypic.com/30tow9u.jpg

http://oi43.tinypic.com/143j62s.jpg

Just to point out, we have checked for blown caps and as far as we can tell there aren't any.

Also, it's worth noting that when i turn the tv on it does not always display a picture for a split second like i mentioned in the original post, on most occasions it does but on other occasions you just see backlight turn on and then it goes completely black again, similar to when the picture is shown for a split second.

Thanks.

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

Anyone?

[tom66]

Re: Saumsung le40b554m2w; Sound but no picture

When it does go blank can you still see a faint glow from the screen backlight or does that go?

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

Hi, thanks for the response.

It seems to go completely blank, when you initially turn the TV on the backlight (when the picture does not display for that split second) is significantly apparent and then just seems to switch off and go blank.

I've just done another test by holding up a torch in a dark room, the first time i did this i was under the impression that there was no picture but the test i just did now there quite clearly is a picture. This suggests it's a backlight issue right?

[tom66]

Re: Saumsung le40b554m2w; Sound but no picture

BN44-00264C is your power board part #.


Pin 23 of CN801 (goes to main board) is inverter on/off. Check this.

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

I'm getting 3v for the inverter.

Not sure if this is worth noting or not, but when testing various pins the backlight (not the picture) for a split second on occasions turns on, although this is not consistent to any specific pin and does seem to my knowledge rather random.

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

Hi mate, is that reading suitable for the inverter pin? Any idea on what i should do next?

Thanks.

[tom66]

Re: Saumsung le40b554m2w; Sound but no picture

That is good. Now, check the voltage across the large 450V capacitors. What do you see? Should be in the region of 380V to 400V. Be careful: you are checking on the high voltage primary side. Do not touch anything on the primary of the power supply and be careful not to let your probes slip.

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

Ok so i've measured both and both capacitors measure at 280v.

[budm]

Re: Saumsung le40b554m2w; Sound but no picture

"280V' is way too low, even when the PFC is not kick in, you should have around 320~330VDC on the cap. Is the meter OK? You measured the voltage right at the two legs of the cap?

[newtothis]

Re: Saumsung le40b554m2w; Sound but no picture

DMM set to AC or DC?

[tom66]

Re: Saumsung le40b554m2w; Sound but no picture

Also check meter battery. And incoming mains voltage, could be very poor house wiring.

[newtothis]

Re: Saumsung le40b554m2w; Sound but no picture

Also check meter battery.

Not with your DMM though LOL (sorry have to put fun into this repairing malarky!)

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

Hi, sorry guys, was using an old analogue multimeter yesterday that seems to be for whatever reason faulty. So switched to a digital multimeter today and both caps measure at 389V.

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

Hi, any suggestions on what i should try next?

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

anyone?

[donst]

Re: Saumsung le40b554m2w; Sound but no picture

Anyone, please? Would be greatly appreciated. As we have identified the backlight to be the issue, would simply switching the bulb for the backlight possibly work?

[tom66]

Re: Saumsung le40b554m2w; Sound but no picture

Ahhh sorry totally missed your posts. Please identify if there is a small black, 4 legged device on your board labelled PCI801S. It will cross the boundary between primary and secondary. If so, please check the voltage between pins 3 and 4, the only two leads on the secondary side.