Seiki SE40FY27 Bad LED Strip help..

[102mm]

Picked up a Seiki SE40FY27 that has 1 Bad LED strip. The set powers of but one strip of LEDs blink intermittently. I have tested the voltages and swapped the lights to be sure it was the strip.. now the problem is how do i determine which LED is actually bad? I tested every light on the strip using the diode meter on my DMM and each one lit with the same brightness.. I get the same brightness when testing the LEDs on a good strip too . Is there something i can do besides changing every LED on that bad strip?

The attached image shows the top strip off. It's actually flashing but my camera isn't fast enough to catch it while its on..

[ReeceyBurger123]

Re: Seiki SE40FY27 Bad LED Strip help..

Remove the plastic optic off the top of the led diodes, you can just twist them off and then the led diode will be exposed. Then you can use a DMM in the diode mode. Find the polarity of the led then reverse bias the meter probs so that the red (positive probe) goes to the negative of the led and the black (negative meter probe) goes to the positive end of the led. If the led is good it will light but very dim if its bad it wont light at all.
You will then need to find the spec of the led and find a new diode or use a zenerdiode to substitute it. After ward just a case of re-sticking the optic down with hot glue.

[ReeceyBurger123]

Re: Seiki SE40FY27 Bad LED Strip help..

Re-reading the post sounds like you have a di-bond failure on one of the leds. The pain is that when the faulty one goes intermittent it takes down the whole strip. Best to probably try tapping each led or near it on the trace of strips to see if any of them when vibration is near them fail and take out the strip. I had to do this on a 32" LG was a nightmare.

[102mm]

Re: Seiki SE40FY27 Bad LED Strip help..

If the led is good it will light but very dim if its bad it wont light at all.

That's my problem.. each one lights up like it's fine when i test it with the DMM, but the strip blinks when powered up and when it's flashing ALL the LEDs come on with equal brightness. it's weird..

[102mm]

Re: Seiki SE40FY27 Bad LED Strip help..

Re-reading the post sounds like you have a di-bond failure on one of the leds. The pain is that when the faulty one goes intermittent it takes down the whole strip. Best to probably try tapping each led or near it on the trace of strips to see if any of them when vibration is near them fail and take out the strip. I had to do this on a 32" LG was a nightmare.

we were replying at the same time i see... Thanks i'll try that. I was thinking of just replacing them all.. i Have some LEDs that look very similar to what's installed..

[102mm]

Re: Seiki SE40FY27 Bad LED Strip help..

Well... I tapped with no luck... i replaced the LEDs and they started smoking.. so i re-soldered the old LEDs back on the board and now that strip does not even light up, but when i test each one individually they light up... the polarity is correct so i don't know what the problem is..

[ReeceyBurger123]

Re: Seiki SE40FY27 Bad LED Strip help..

Or even better if you get a can of compressed air hold the can upside down so that the refrigerant will come out and spray the leds. This works just as well.

[lookimback]

Re: Seiki SE40FY27 Bad LED Strip help..

Are you testing by probing the LED, or the strip? If you have a bad solder joint, probing the LED will still make it come on, but probing the strip just beyond the solder pads won't (use sharp probes to pierce the solder mask). How did you do the LEDs btw? My method is to wrap a piece of tin foil around the strip, leaving just the area the LED occupies exposed on the top. I add a bit of solder to each pad, flux, set the LED in place, then heat from the bottom with my hot air wand until the LED sucks down into place. It will discolor the white solder mask, but the tinfoil prevents the back of the board from burning.

[ReeceyBurger123]

Re: Seiki SE40FY27 Bad LED Strip help..

Are you testing by probing the LED, or the strip? If you have a bad solder joint, probing the LED will still make it come on, but probing the strip just beyond the solder pads won't (use sharp probes to pierce the solder mask). How did you do the LEDs btw? My method is to wrap a piece of tin foil around the strip, leaving just the area the LED occupies exposed on the top. I add a bit of solder to each pad, flux, set the LED in place, then heat from the bottom with my hot air wand until the LED sucks down into place. It will discolor the white solder mask, but the tinfoil prevents the back of the board from burning.

Are you talking to me ?
If so when I repaired the ones I worked on I used aluminium tape, removed the optic. Added some Chip Quik flux (best for smaller joints) then used my 858d hot air station and the smaller tip on 350dc and heated the led diode, swiped it off with tweezers. Put the new one on and added a very tiny bit of solder. Finally clean the strip off with IPA and remounted the optic and boom

[lookimback]

Re: Seiki SE40FY27 Bad LED Strip help..

Are you talking to me ?

No, I was asking 102mm.

Aluminum tape is good too, does the same thing. I use tinfoil for everything when working with hot air though, just because there's always a roll in the kitchen.

[ReeceyBurger123]

Re: Seiki SE40FY27 Bad LED Strip help..

No, I was asking 102mm.

Aluminum tape is good too, does the same thing. I use tinfoil for everything when working with hot air though, just because there's always a roll in the kitchen.

Hahaha fair enough

[lookimback]

Re: Seiki SE40FY27 Bad LED Strip help..

Hot glue for reattaching the optics is a great idea too. I've been using heat sink cement. I just saw a glue gun in my basement too. Now I will have to go look for it.

[ReeceyBurger123]

Re: Seiki SE40FY27 Bad LED Strip help..

Hot glue for reattaching the optics is a great idea too. I've been using heat sink cement. I just saw a glue gun in my basement too. Now I will have to go look for it.

Yeah I use hot glue as it dries almost instantly meaning that the optic wont be able to move at all.

[lookimback]

Re: Seiki SE40FY27 Bad LED Strip help..

Definitely beats watching the other stuff dry for 45 minutes.

[Louis82]

Re: Seiki SE40FY27 Bad LED Strip help..

Hello there,

I have this tv on my bench. Sound but no picture, I can see image using flash light. Not sure If I have a led strip problem. All voltages going to led strips (see picture - connector on right top) go up to 80v then slowly drop to 30v. When I disconnect LED strips from power board, I get 25v on pin 1, 3, 5. Budm always suggest to check the filter cap, AND my filter cap measures only 163v (150uf 400v). I believe my problem is on the circuit board. Any suggestions?

[Louis82]

Re: Seiki SE40FY27 Bad LED Strip help..

Any one? The circuit board that appears on picture I attached is actually the only circuit board on this tv. Not available for an affordable price anywhere.

[budm]

Re: Seiki SE40FY27 Bad LED Strip help..

The board does not have PFC Voltage booster so 160VDC reading on the cap is normal for this one.
Can I see closed up pictures around the LED connector top and bottom side of the board?
Also the whole bottom side of the board, straight shot.

[Louis82]

Re: Seiki SE40FY27 Bad LED Strip help..

Here are pics budm. Thanks

[budm]

Re: Seiki SE40FY27 Bad LED Strip help..

There are two electrolytics caps close by yhe LED connector, what are the Voltage rating printed on them?
BTW, the LEDs are connected in series as one big long string.

[Louis82]

Re: Seiki SE40FY27 Bad LED Strip help..

47uf 100v