Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

[jeanph01]

Hi,
I found this 40'' tv (Samsung lnr408dx/xac, made in 2005) near a trash in front of an electronic store and brought it home.

I plugged it and got a little electronic melody and the backlight seems to be working since there is a little glow that appear but there is no image. It's black. I plugged a VGA connector and connected it to my computer and Windows recognized the screen as a Samsung TV. So some electronic seems to be OK.

After looking on YouTube I learned about the bulged capacitors problem. I opened the TV and yes there was two small bulged capacitors that I replaced with new ones with same same specs : 25v/1000uf.

But still the screen keeps being black. I wonder if it's the t-con board??. How could I know ? Can it be fixed by hand with some soldering ?
I thought about buying a multimeter and testing the different components but i'm not sure what to test.
I really want to repair it though...

Thanks for any advice ! :-)

[tom66]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

This is a pretty common issue with this series of TV.
There's a small fuse on the T-con which tends to blow from age/heat/poor design, replacing it usually fixes the problem.
To begin can you take a picture of the T-con?

You -will- need a multimeter to do the required tests. Beg, buy or borrow one -- even a $5 one works.

[jeanph01]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

Thank you for your reply. I managed to access the T-con board and I have included a picture here : https://www.dropbox.com/s/pyic7mjcrm...-17-48_HDR.jpg
I don't see any fuse though. I finally bought a multimeter and tested every removable fuse I could find on every board but every one of them (there's 4) seems to be fine.
Here's a picture of the whole set :
https://www.dropbox.com/s/aa55hvzoqq...-27-34_HDR.jpg

And close-up pics of the t-con board :
https://www.dropbox.com/s/s4r7dy407v...-32-53_HDR.jpg
https://www.dropbox.com/s/m19imy797n...-33-10_HDR.jpg


Thank you for your help.

[tom66]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

The fuse in this case is "CP".
https://www.dropbox.com/s/s4r7dy407v...-32-53_HDR.jpg
near left hand side board and that connector on the left hand side.
Test the voltage on both sides. DMM on 20VDC scale, black probe on metal chassis, red probe on each end. TV should be ON with backlight.

PS. Thanks for the good pictures.

[jeanph01]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

Ok. First thank you for your help.
I did what you asked. Here's the result:
5.38 on the left side and 0.24 on the right side. I presume this is in Volts.
Also:
The backlight is definitely working. Here's a picture i've taken of the open Tv in the dark :
https://www.dropbox.com/s/7yufd4txyo...316_193119.jpg

But, i noticed a hissing sound. I made a recording of it with the power on and off chime in case it could help to diagnose another problem. Here:
https://www.dropbox.com/s/98cc0tccez...ocal%20002.wav

Thanks.

Ps: I accidentally touched the connector with the red probe while doing my test and there was a spark. The TV shut down immediately then started again half a second afterward and everything was 'normal'. Is this a protection again short circuit ?

[tom66]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

The fuse is blown.
Replace it with this:
http://www.digikey.com/product-detai...98-1-ND/615060

I hope no damage is done by doing that, it is probably OK if original symptoms are identical.

[jeanph01]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

God this fuse is tiny. Do you have a way to solder it without covering the whole chip with solder ??!! I searched the whole internet and youtube and found nothing to show me how to do it.

Thank you.

[budm]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

You do not need to remove the blown fuse, just stack the new one on top and solder each end to the old fuse.

[jeanph01]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

Just to say thank you... The TV's working and the humming hissing sound disappeared when I plug a vga/hdmi source.
Here's my family watching netflix on it :
https://www.dropbox.com/s/qbsz7jvr1y...2018.23.14.jpg

Thanks again !
Ps: that cp fuse looks like a programmed obsolescence from Samsung. What do you think ?

[tom66]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

Nice to see one man's trash become another's treasure

It's more like bad design, but it's simple to calculate the life of a fuse. (Many published equations on this, especially look up MIL SPEC from US military which has useful calculations for this.) So it's possible that Samsung did calculate a deliberately a short life but more likely they didn't calculate it at all and guessed the value or assumed it worked for one month so would last forever. And without true manufacturer-backed warranties of longer than a year, Samsung has no incentive to make sure the fuse will last.

I view Samsung as a "mid-tier" manufacturer. They don't produce the worst stuff, but have enough failures and problems for me to advise against buying any Samsung products. Of course after fixing them I have no problem with using them, I'm watching one now .

[heavymachines]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

thanks help- me fix this same model in like 30 mins awesome forum...thanks

[00g]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

The fuse is blown.
Replace it with this:
http://www.digikey.com/product-detai...98-1-ND/615060

I hope no damage is done by doing that, it is probably OK if original symptoms are identical.

Tom66, I love you man.
This worked perfectly.

I found this tv by the dumpster in my neighborhood. Now I have an extra 40" (that I have no use for).

The part was 31 cents. Delivery was quick even with standard USPS.

P.s. I was reading 5.3 on one side of the fuse 0.5 on the other.

[jeff6763]

Re: Samsung lnr408dx/xac, no image, backlight ok, changed 2 capacitors

This is a pretty common issue with this series of TV.
There's a small fuse on the T-con which tends to blow from age/heat/poor design, replacing it usually fixes the problem.
To begin can you take a picture of the T-con?

You -will- need a multimeter to do the required tests. Beg, buy or borrow one -- even a $5 one works.

tom66 , thank you very much, this really helps me resolved the same issue on the samet TV model, but another problem came out now, before I was able to use the hdmi port with my Acer tablet and worked well, but now NO Signal detected. I wonder what happened to this and what could be the solution,

thanks