Samsung lcd tv

[monkeyelectric]

Evening all, would any of you kind people know what the cause would be for my samsung 40 " tv to have sound but no picture? There's nothing there, the screen is just black. It was working quite happily yesterday but i've just got in and switched it on and this has happened.

 

[monkeyelectric]

Ok seems to be a common fault, no back light and picture but sometimes sound. which is supposed to be invertor psu, Now i`m no expert on tvs, but have used this company before to buy repair kits for sky etc, with no problems, but your gonna have to be good at soldering, because these are small components. Repair Kit126 £22 form Ohms click on link
OHM SUPPLIES ltd, LCD & PLASMA REPAIR KITS AND SPARES

Great link there mate cheers, i'm not bad at soldering so i'll give it a go as i don't want to throw the bugger away just yet

 

[tazz]

No Problem, what these kits have is all possible components which could go wrong, in that section of the board. Good luck and keep us all informed how you get on.

 

[wade88]

 

[DPG]

Don't be too scared by surface mount components. As long as you're steady with them you'll be fine. Unless you need to start changing ICs - that's more fun. Especially BGAs! Never liked doing them, and you certainly can't do them with a soldering iron Daz

 

[Deleted member 38070]

Maybe a little anorak, but here goes...Probably the backlight not coming on, the inverter gets fed with 24v dc from the power supply, it generates a stupidly high ac voltage for the cfl back lights, the back lights are switched on via a 5v coming from the main processor. So going onto the inverter you should have 24v (or 12v) dc and the "on" 5v from the processor. Usually the board will have printing near the plug that tells you the voltage.. You can put 5v on the pin to fire the screen up (you'll probably see a dark stripe across it as one of the back lights is probably gone) that's if you have the supply voltage coming from the psu...(at your own risk! I have done this) Look for capacitors bulging on top, that's quite a common one. The inverter in LCD TV knows how much current is being drawn by the back lights, it then knows if there's a cfl out.. You can hang a scope near the inverter output and pick up the kv ac waveform. Its at about 30khz If you see it come up then go (or the 5v come up and go) then your backlight is faulty only way to fix this is new/replacement screen (eBay)
Or probably time for a new tv!
If its led backlit, then who knows..???
Some of the newer samsungs have one board for the psu and inverter, you'd need a circuit diagram, if you could find one!
(older ones had psu, signals and inverter boards.)
you could search eBay for the inverter board (part number is on the board bn.....) and give it a go, it might be the inverter faulty.
imo. Screen

hope this helps.

 

[monkeyelectric]

post me it and I will fix it.....or I can advise from a photo of the circuit board and a short description of the issue...

Hi Grant was that aimed at me with my tv or Archy with his power supply?

 

[monkeyelectric]

Right, the back is off again and i have no bulging capacitors, i've got no means of testing them Either as my multimeter does not have the setting for them. Smiffy, not 100% on where i should be looking for the voltages you describe? I'm interested in finding out where the fault lies and how to test different components in it so i don't really want to just take it to a tv repair shop and £100 later its working, i'm very inquisitive

 

[Silly Sausage]

Hi Grant was that aimed at me with my tv or Archy with his power supply?

I think it was me Monk.
Thanks anyway grant, it just needs four caps replacing, when I can get my hands on them.

 

[grantr37]

4 radial elecro ones? what values and V's and I will have a rummage around in the boxes next time I'm in the spark lab......

I prefer to use self fluxing silver solder when re-doing electrolytic caps, then I put a dod of hot melt glue on the side to fix them as well....silver solder gives a good contact with the surface on the track pad once you have the old solder off with de-soldering braid....no need for laquer spray or anything

Another thing I do is to use the (red) hot run caps (rubycon or similar) which have a good tolerance to the heat build up of the inside of a power pack....they are made for hot running, power packs are hot running in a lot of instances...standard capacitors dry out a lot more quickly...

if you ever have dried caps in a power supply and need temporary use in an emergency until your spares arrive(or your new power pack, if not keen on repairing) for example to use your laptop then an old trick is to tie the power pack (minus the mains lead if it detaches preferably) into a carrier bag, put it into the freezer for 45 minutes, take it out and it will work, after switching off, it will not work again unless you stick it back in the freezer, but as long as it is powered on it will function.....this is just a last resort fix and obviously you would be better to unplug after every use and go to the freezer trick each time round until either repaired or replaced.....don't ever let the power pack get wet...

using the freezer to chill the unit alters the electrolyte properties of the remaining electrolyte in the capacitors and brings it within functioning levels for a single use, once run up to working temperature this needs to be redone after unplugging/switching off...

45 minutes is a good time to allow the cold to work it's way through the casing and into the metalwork, components etc.....but forgetting about it and leaving too long can result in bursting of capacitors and condensation inside that can cause damage...so 45 minutes is ideal...

 

[Silly Sausage]

Cheers G!
After hours of trawling RS I found suitable jobbies, but now I think I've lost me part numbers!!! Numpty!
The thing is a Time Capsule or something, but she now saying she just wants the disc, so we'll see!
What an appalling design the thing is though, from heat dissipation view!.
We took it to an Apple centre the other day, guy just says it's dead, REALLY! Wan......

addition

Good to know there's some electronics geezers on here, prepare to get brains picked!

 

[GLENNSPARK]

4 radial elecro ones? what values and V's and I will have a rummage around in the boxes next time I'm in the spark lab......

I prefer to use self fluxing silver solder when re-doing electrolytic caps, then I put a dod of hot melt glue on the side to fix them as well....silver solder gives a good contact with the surface on the track pad once you have the old solder off with de-soldering braid....no need for laquer spray or anything

Another thing I do is to use the (red) hot run caps (rubycon or similar) which have a good tolerance to the heat build up of the inside of a power pack....they are made for hot running, power packs are hot running in a lot of instances...standard capacitors dry out a lot more quickly...

if you ever have dried caps in a power supply and need temporary use in an emergency until your spares arrive(or your new power pack, if not keen on repairing) for example to use your laptop then an old trick is to tie the power pack (minus the mains lead if it detaches preferably) into a carrier bag, put it into the freezer for 45 minutes, take it out and it will work, after switching off, it will not work again unless you stick it back in the freezer, but as long as it is powered on it will function.....this is just a last resort fix and obviously you would be better to unplug after every use and go to the freezer trick each time round until either repaired or replaced.....don't ever let the power pack get wet...

using the freezer to chill the unit alters the electrolyte properties of the remaining electrolyte in the capacitors and brings it within functioning levels for a single use, once run up to working temperature this needs to be redone after unplugging/switching off...

45 minutes is a good time to allow the cold to work it's way through the casing and into the metalwork, components etc.....but forgetting about it and leaving too long can result in bursting of capacitors and condensation inside that can cause damage...so 45 minutes is ideal...

but works at high tempretures

 

[grantr37]

Cheers G! After hours of trawling RS I found suitable jobbies, but now I think I've lost me part numbers!!! Numpty! The thing is a Time Capsule or something, but she now saying she just wants the disc, so we'll see! What an appalling design the thing is though, from heat dissipation view!. We took it to an Apple centre the other day, guy just says it's dead, REALLY! Wan...... addition Good to know there's some electronics geezers on here, prepare to get brains picked!

I have detailed files..... but that makes you a more efficient fixing machine... Affirmative....

 

[Silly Sausage]

You will be assimilated.

 

[grantr37]

Evening all, would any of you kind people know what the cause would be for my samsung 40 " tv to have sound but no picture? There's nothing there, the screen is just black. It was working quite happily yesterday but i've just got in and switched it on and this has happened.

pop a good photo of the Circuit board on here if you can, would be good if there is a bit of a closer photo of the board where the cable to the screen is connected as well......then I can get to scheming up a repair plan...

 

[GLENNSPARK]

You will be assimilated.

he already has...that happened the minute he decided to come in here...