Post The Led Backlights Your Fixing Here.

[reeferman]

Re: Post The Led Backlights Your Fixing Here.

Samsung UN55F6400. 3 RH strips had bad LED's. Two strips each had 1 bad, one had 3 bad,
After replacing the 3 on one strip, I had to replace 4 more!
3 volt 3535smd led

[Vista20]

Re: Post The Led Backlights Your Fixing Here.

I'm replacing my edge LEDS now. Samsung UN55D6050TFXZA. The part # on the LED strips is 2011SVS55-FHD 5k6k, left and right.

I noticed there was some double stick tape on the rail in front of the LED strips, but did not appear to adhere to the LED strips. Is that double stick tape there to better secure the flat panels?

I bought a roll of double stick tape from ShopJimmy.com.

I think I can replace everything properly once my LEDs are reinstalled and connected. I bought some new screws to secure the LED's because the ones holding in the old strips were tough to get out and the Phillips head stripped
on several of them in the process.

Does anyone know of a tutorial on replacing these types of LEDs, just in case I need a reference?

[budm]

Re: Post The Led Backlights Your Fixing Here.

Yes, I set the voltage at 24V (3V for each LED) and 800mA limit (100mA) for each LED.
When I applied the probes to the sets of LEDs the power supply showed 60-70mA, I was expecting it to hit the current limit but it wasn't close.
Testing a handful of individual LEDs with the voltage set at 3v and the current limit 100mA, I see current draw between 40mA to 80mA
Why do 8 LEDs draw as much current as a single one ? I'm confused, what am I missing ?

1) Series circuit: same amount current will flow through all 8 LEDS, you do not add the current for each load in the SERIES circuit.
2) As I indicated, not all 8 LEDs will have the same Vf.
2) As I indicated, if you slowly crank up the power supply Voltage of that power supply, you will see the current starting to rise sharply. Did you do it as I suggested?
You will learn a lot by doing the proper experiment.

See page 10 of the LG LED spec then you will see why.
LED is not linear device, you can how much current will change with small amount of change of the Voltage.
Per chart @3V If is about 80ma, @3.2V it goes over 150mA.
The spec. on page 5 also show Vf of 3V @65mA.
The Vf of the LED in the working TV will be higher than 3V because the If is in the range of 200 ~ 400 mA range.

[dskall]

Re: Post The Led Backlights Your Fixing Here.

I was thinking about this subject the other day because it was confusing me to. Of course it is just ohm's law. I am just learning this stuff.

[diif]

Re: Post The Led Backlights Your Fixing Here.

Current is same throughout series circuit. Each led will have same current. But voltage will have to change each time you add led to maintain current

Of course ! I'm confusing myself unnecessarily. It's been a very long time since i did any electrical theory, thanks for jogging my memory. I went and had a little read too.

[dskall]

Re: Post The Led Backlights Your Fixing Here.

Current is same throughout series circuit. Each led will have same current. But voltage will have to change each time you add led to maintain current

[diif]

Re: Post The Led Backlights Your Fixing Here.

Yes, I set the voltage at 24V (3V for each LED) and 800mA limit (100mA) for each LED.
When I applied the probes to the sets of LEDs the power supply showed 60-70mA, I was expecting it to hit the current limit but it wasn't close.
Testing a handful of individual LEDs with the voltage set at 3v and the current limit 100mA, I see current draw between 40mA to 80mA
Why do 8 LEDs draw as much current as a single one ? I'm confused, what am I missing ?

[budm]

Re: Post The Led Backlights Your Fixing Here.

I have no idea of the spec of the LEDs but my LED tester ramped up to 22.7v per set of 8, so I figured they were 3V LEDS, hence the 24V.
The current did seem low, but they are bright at 3V, maybe they are 6V though.

But I thought you use 24V power supply with current limit to 800mA.
The LED tester only put out about 30mA that is why you see total Vf of only 22.70V, they are 3V LED at higher current.

[dskall]

Re: Post The Led Backlights Your Fixing Here.

Vizio will drive theirs around 400ma which is why they don't last. Funny thing is you can modify current to about half and they are still plenty bright. Makes you wonder if it is preplanned obsolescence.

[diif]

Re: Post The Led Backlights Your Fixing Here.

I have no idea of the spec of the LEDs but my LED tester ramped up to 22.7v per set of 8, so I figured they were 3V LEDS, hence the 24V.
The current did seem low, but they are bright at 3V, maybe they are 6V though.

[budm]

Re: Post The Led Backlights Your Fixing Here.

I tested with my LED tester and thought the same.
I then used my bench tester set at 24v and set the current limit at 800mA, tested on each set of 8 LEDs they are drawing 60-70mA. Seems they are not drawing much current.

You should see the current goes up much higher once you turn up the Voltage beyond 24V (I would limit the current to 100mA first) since the Vf of all 8 LEDs may not be 3V exact, some may be higher or lower you will have to look at the spec sheet of the LED.

[dskall]

Re: Post The Led Backlights Your Fixing Here.

I think panel drives them alot harder than 60-70ma

[diif]

Re: Post The Led Backlights Your Fixing Here.

Of course if you were using an led tester to check. Main drawback is they don't drive the led's very hard. So may not break down under light load.

I tested with my LED tester and thought the same.
I then used my bench tester set at 24v and set the current limit at 800mA, tested on each set of 8 LEDs they are drawing 60-70mA. Seems they are not drawing much current.

[dskall]

Re: Post The Led Backlights Your Fixing Here.

A total of 92 LEDs in this Sony 46", edge lit top and bottom. Removed all 4 strips, but nothing faulty round. Wondering if it was a dodgy connection..

Of course if you were using an led tester to check. Main drawback is they don't drive the led's very hard. So may not break down under light load.

[zdsh07p9]

Re: Post The Led Backlights Your Fixing Here.

I've been fixing TV's on the side for 12-13 years now ever since I was 14. My Dad had a Vizio 42" under his bed that was broken that I fixed with 2 caps and that started it all! Anyways - heres a list of TV's I've fixed LED's in within the last month - prepare yourselves lol:

Vizio e470i-a0
Hisense 50h5g
Sharp LC-60LE681u
Samsung UN75F6300 - yes you read that correctly. I replaced these by myself with no special contraption.
Vizio P502ui-B1E (this was because of an issue with the LED Driver board, not the actual LED's themselves)
LG 47LN5400

Anyways, the broken TV market has been pretty good to me lately.

[diif]

Re: Post The Led Backlights Your Fixing Here.

Have you tested the leds from the plug connection to see if they light up
or led to led.
Had it on a samsung where the leds tested fine.
but from the plug ta section would not light up
turned out to be a burnt trace.

Tested from the 15 pin connectors and also the 6 sets of 8 LEDs on each of the strips.
Think I'll reassemble and test without the LCD screen, it's possible one of the ribbon cables wasn't located properly or is damaged. Or it's the driver board.

[zomi]

Re: Post The Led Backlights Your Fixing Here.

Have you tested the leds from the plug connection to see if they light up
or led to led.
Had it on a samsung where the leds tested fine.
but from the plug ta section would not light up
turned out to be a burnt trace.

[diif]

Re: Post The Led Backlights Your Fixing Here.

A total of 92 LEDs in this Sony 46", edge lit top and bottom. Removed all 4 strips, but nothing faulty round. Wondering if it was a dodgy connection..

[nwcs]

Re: Post The Led Backlights Your Fixing Here.

I have repaired hundreds of led's in tv's and they almost always come back with more bad so I now just replace all of the led strips. And for the first time I had a Samsung UN55ES6100 that when I removed the panel to test the led's the positive wire had come disconnected from one led strip and that caused what I thought would be a bad led strip.

[diif]

Re: Post The Led Backlights Your Fixing Here.

I see a lot of posts where 1 or 2 led's are replaced. Given that the remaining led's are all the same age, and a strip of 100 on a slow boat from China is very inexpensive, would it not be prudent to just change all of them at the same time ?

I wouldn't want to swap all 52 LEDs in the last couple of TVs I've repaired the LEDs on. Replaced the dead one, turned the back light down and that's it.