Samsung LE40B620R3W no back light

[24mech]

Good morning Badcaps, is everyone ready for the silly season lol.

I'm hoping for some advice please, I have an LE40B620R3W when the unit powers up you get all the right chimes and the screen shows the channel for a brief second then the screen goes black I have used the light trick and can see that video is there just no back light, the sound is ok no issues there. I have had the back pannel of and taken the power/inverter board BN44-00264A out it looks like someone has had a go at repairing this previously.
Thats the history so my questions are:-
1. Does the fact that the screenlights up briefly when started point to a board problem or is it more likly to be a back light issue.
2. If its a board issue and the fact its already been repaired would I be better of replacing the board?
3. Is there a way to confirm board or backlight before going any further.

Thanks in advance for your help

[Hamie]

Re: Samsung LE40B620R3W no back light

Does the mainboard still send the BL-ON signal when the backlights cut out?

[Hamie]

Re: Samsung LE40B620R3W no back light

Btw on this power supply you don't need to 'jump it on'

If you disconnect the mainboard from the power supply and plug it in.
The backlights will come on, and should stay on until you unplug it.

[24mech]

Re: Samsung LE40B620R3W no back light

Thanks for your reply, I will try this when I get back later this afternoon and report back the results. I take it if the lights come on it will be a board issue I'll take some pictures of the board as well to get peoples thoughts on repair v's replace Thanks for the response Hamie

[24mech]

Re: Samsung LE40B620R3W no back light

Hi there again people, I took some pictures of the board, I disconected the main board from the av so it only had the 240v power plug conected and powered it up, no back light did I do this correctly or? also it looks like several items have been replaced on this board already, what do you think?

[budm]

Re: Samsung LE40B620R3W no back light

What is the P/N of the power supply/inverter board combo? BN44-?????

[johnboy1313]

Re: Samsung LE40B620R3W no back light

Bud, that's a BN44-00264A.

24mech, follow the instructions in this thread to pull up the service menu to get to the test patterns. With a fully white screen, you should be able to see which bulbs aren't firing. Then, test that transformer against the others to see if it measures bad. I haven't seen a lot of bad transformers on the 00264A board. The 00264B board is a different story. My guess is that you have at least one bad bulb.

https://www.badcaps.net/forum/showthread.php?t=29580

[24mech]

Re: Samsung LE40B620R3W no back light

Good morning once again thanks, johnboy1313 I have read the thread you linked to my back light does not come with the 30p disconected, are you surgesting I bridge out CI805 or CI806 to get the back light to come on?

[24mech]

Re: Samsung LE40B620R3W no back light

Ok so I bridged out CI806 and we now have a back light it looks like the upper bulb isn't working and after being on for just a little while it started to smell hot, looking closer the inverter transformer for that bulb TI801S was a lot hotter than the other 3 is it worth my time swapping this with one of the others to see if the fault moves?

[24mech]

Re: Samsung LE40B620R3W no back light

I've swapped TI801S with TI803S and rebuilt the unit (trying to identify bulb or board issue). I have carried out the master test and these are the results (CI806 is still bridged out) I noticed that none of the transformers are notably hotter can someone point me in a direction to go next as it looks liike swapping the transformers has helped but I'm not sure what to do next.

[johnboy1313]

Re: Samsung LE40B620R3W no back light

I would test the primaries and secondaries of each transformer and compare the readings against each other. If one transformer is noticeably different than the rest, I'd suspect a bad transformer. Personally, I still suspect bad bulbs.

If the one transformer isn't getting hot anymore, maybe you had a bad solder joint that you corrected by swapping the transformers. Have you tried to remove the bridge at CI806?

[24mech]

Re: Samsung LE40B620R3W no back light

I've removed the bridge and the problem came back, if its a bulb how can I test it? are they easy to replace?

[johnboy1313]

Re: Samsung LE40B620R3W no back light

Replacing them involves opening the panel. It's not difficult but it could lead to a damaged screen if you're not careful, which would basically make the TV a box of parts. You'll have to strip the panel to the metal box, leaving the power supply connected. Then remove the metal frame around it by removing several screws and carefully lifting the frame. I wear rubber gloves to remove the screen and lay it on a blanket on a flat surface up away from any kids or pets. The black plastic under the edges of the screen (you'll see it when you get there) will probably have a few screws holding it together as well but it might just snap together. Once that's removed, you can pull the diffuser layers. Keep these together and do not mix up the order. They need to be put back in the same order as they came out. At this point you'll see the bulbs. I use pieces of wood to keep the panel lifted off of the table enough so the power supply isn't supporting the weight of the panel. I suppose you could use a sturdy art easel too. That way you'd have access to both sides of the panel as you work. Plug the set in and observe which bulbs don't fire. Make sure your solder bridge is still there. I can't remember if the bulbs are soldered in or if they are clipped in. Either way, it isn't difficult to swap them out. I found a 40" Sony with a cracked screen to scavenge bulbs from locally on Craigslist. Another guy on here bought six bulbs for 5 pounds at a TV repair shop in his neighborhood.

The main points are just be careful and put everything back together the same way it came apart.

Go for it.

[24mech]

Re: Samsung LE40B620R3W no back light

Well I've got it this far (though I wasn't the first to do so the seals were already cut) and it looks like 1 dead one and a few on there way, how do I test the bulbs?

[budm]

Re: Samsung LE40B620R3W no back light

You have lots of bad/worn lamps with blackened ends and those ends got hot to discolor the white plastic shield.
Also remove that white plastic shield to see if they also have ballast caps.

[24mech]

Re: Samsung LE40B620R3W no back light

Hi there I have removed the plastic's and the bulbs at the inverter end look corroded? do I need to replace them all and where can I get thwm from, I've looked on ebay without success :-(

[johnboy1313]

Re: Samsung LE40B620R3W no back light

I was in a very similar predicament with my set as well. You're likely gonna want to replace all 14 bulbs or face digging into it again in the near future. Just to be sure, I would swap the dead bulb with a working one to see if the dead bulb stays dead in a new location. That will rule out the transformer for sure.

[budm]

Re: Samsung LE40B620R3W no back light

You need to clean all the lamp sockets and replace ALL the lamps if it is worth it for 40" TV, they probably had set the backlights level at full blast.

[24mech]

Re: Samsung LE40B620R3W no back light

Ok where can I get bulbs from and whats the cost likly to be does anybody know?

[vinceroger69]

Re: Samsung LE40B620R3W no back light

you would need to measure the diameter of the tube and the lengh of them first