How do I find exact replacement LED bead for this backlight strip? and will it last?

[link626]

How do I determine what type of LED this is? I wanna buy some off ebay

and I heard that if you replace the LED, eventually the whole strip will fail anyway. What's the reasoning for this?

[CapLeaker]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

and I heard that if you replace the LED, eventually the whole strip will fail anyway. What's the reasoning for this?

Well, this isn't fully true, but not fully wrong either. LED's are current controlled, not voltage controlled. So when a LED fails, the other LED's in the string have to work harder and get over volted and they don't like that at all. Depending on how long the LED string is, if one LED fails may matter more or less. In your case, we don't know the size or model number of your TV, so have no idea how long your LED string is nor a better idea on what exact LED that is either.

[link626]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

I thought there was a way to measure the LED.

But my TV is a TCL 43s405.

part # LB4308, TOT_43D2900_3X8_3030C_D6T-2D1_4S1PX2 <<< oh damn. 3030 might be a clue. Are all 3030 LEDs the same output? What color temperature are TV backlights usually?

and the strips look like this...

[link626]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

I also tried to test the individual LEDs with a 3V battery with 2 needle probes, and no matter where I scratched off the white paint and put the leads, I couldn't get any LED to light up.

This strip has confusing lead pattern.

I put the probes at the X's...




And my probe tester....

[budm]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

You have 4 strips so how many strips are not lighting up when they are connected to the TV? What Voltage do you have on LED+ pins and on LED1-, 2-, 3- 4- with all the connectors in place.
https://www.shopjimmy.com/tcl-lb4308...43s405tdaa.htm

https://www.shopjimmy.com/catalogsea.../?q=TCL+43s405

[link626]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

There are only 3 strips, and they all light up on the left side only.

The 4 right LEDS on all 3 strips do not light up. The control board shut that side off.

Without an LED strip tester, I have no idea which LED is bad.

I measured ~60 volts on each +/- pair from the main connector from the power board, and this connector splits off into 3, one for each led strip.




I'm really just wondering if I could do a longterm repair simply by swapping the individual LED, or if minor spec differences will cause it to fail.
I see the 3030 LEDs on ebay are 3V 1W, 350-420mA, 140-160 lumens
30 LEDs for $2.85 shipped.

it would be good practice to solder some.

I'd like to keep using my TV rather than trashing it.

[angelos]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

For me its not the issue to replace the LED but rather to readjust the lens to the right position so that the light striking the diffuser sheets does not make a bright spot on the screen. The focal distance is critical on these sets and very noticeable when done wrong.
Imagine you add your 3 dabs of quick drying epoxy and then position the lens whilst moving the diffuser over it partially to adjust the lens position. That is a nightmare. I can bear it to do 2 or three of these but to replace all 60. You will need 8 hours to do so. Also, i have had a high comeback rate when repairing and replacing only the faulty LED's since all are in series and they have all been stressed equally.
Anybody else have a better idea or is it the best advice to replace all LED's???

[zomi]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

Replace all with new strips
best way really.
Life is too short to mess about with getting lens lined up
Sometimes you have to as repalcments cant be sourced
but you have you ask your self how much is your time worth.

[Diah]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

to me for this 3030 SMT LED i use one sort Only ( Like Tomato ) which it can cover current forward from 250-420 mA. as high power LED and to whom ask of VF it can handle from 3.3 -5 V.

[budm]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

So It only has two return wires, each strip has 8 LEDs (the connector on the strip has two pair of connections for 4 LEDs per sub string: TP1+ & TP2-, and TP19+ & TP20-). The three strips are wired up as two LED strings, each string has 12 LED's.
Since each sub string has 4 LED's each if they are 6V LED then using 3V is not going to be enough to forward bias the LED on to make it start conducting current, you can try with 4.5V first for each LED to see if it will glow faintly. I would replace all new strips myself so I do not have to take the panel apart again down the road.
BTW, what is the Voltage reading on LED+ with ref. to chassis GND?

[link626]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

So It only has two return wires, each strip has 8 LEDs (the connector on the strip has two pair of connections for 4 LEDs per sub string: TP1+ & TP2-, and TP19+ & TP20-). The three strips are wired up as two LED strings, each string has 12 LED's.
Since each sub string has 4 LED's each if they are 6V LED then using 3V is not going to be enough to forward bias the LED on to make it start conducting current, you can try with 4.5V first for each LED to see if it will glow faintly. I would replace all new strips myself so I do not have to take the panel apart again down the road.
BTW, what is the Voltage reading on LED+ with ref. to chassis GND?

ahh, I suspected these might be 6v leds.

Would I be able to use a 5V phone charger to light these up?


How do I test LED+ and chassis GND? Where do I put my probes?

[link626]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

to me for this 3030 SMT LED i use one sort Only ( Like Tomato ) which it can cover current forward from 250-420 mA. as high power LED and to whom ask of VF it can handle from 3.3 -5 V.

If these leds happen to be 3v, 6v led can be substituted? with no decrease in light output?

(I'm sorry, I don't know anything about leds)

[link626]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

Replace all with new strips
best way really.
Life is too short to mess about with getting lens lined up
Sometimes you have to as repalcments cant be sourced
but you have you ask your self how much is your time worth.

yeah, I get it. In the future though, when parts may be hard to find, I will want to replace an led, since a new TV will cost $XXX.

Right now, shopjimmy sells used pulled led strips for this TV.
New parts for this TV are impossible to find.

Also, getting the lens lined up seems easy because the strip has markers to line up with. Scrape it clean, then use e6000 adhesive.

[CapLeaker]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

If these leds happen to be 3v, 6v led can be substituted? with no decrease in light output?

(I'm sorry, I don't know anything about leds)

No.
If you try to get a 6V LED to light up with 3V, that doesn't work. You proofed that one already yourself.

[budm]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

ahh, I suspected these might be 6v leds.

Would I be able to use a 5V phone charger to light these up?


How do I test LED+ and chassis GND? Where do I put my probes?

LED connector has label for each pin.
Put all connector back in place, keep black probe on the chassis, red probe on the LED connector that is labeled with LED+ (the one with red wire r the white wire) then turn the TV on to see how high the Voltage jumps up to and then wait 10 seconds to see how low it goes down to.

[link626]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

LED connector has label for each pin.
Put all connector back in place, keep black probe on the chassis, red probe on the LED connector that is labeled with LED+ (the one with red wire r the white wire) then turn the TV on to see how high the Voltage jumps up to and then wait 10 seconds to see how low it goes down to.

I was wrong before.

both LED+ measure at 80V stable. It starts at 60-70V and gradually rises to 80V.

On each led strip connector, TP1 TP2 measure at 0v,
TP19 TP20 measure at 26V.

I measured the voltage across a single LED at 6.5V, so confirmed this is definitely 6V 3030 LED.



So I go on aliexpress and buy "50pcs Lextar LED Backlight High Power LED 1.8W 3030 6V Cool white 150-187LM PT30W45 V1 TV Application 3030 smd led diode"
for $2.61
and I'm golden?

SMD LED -3030 WHITE
SIZE:3.0*3.0*0.65mm
CAT:190-200lm
CCT:6000-8000K
REF:6.0-6.6V
I(MA):350-700ma
QTY:50pcs
High Power LED - 1-2W

I watched some youtube videos, and one guy did some current adjustment after replacing some LEDs.
I hope I don't have to do that, cuz I don't have the tools.

I measured the current across one LED at 290mA.

Will the LED specs quoted above work?

[capwizard]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

In theory, You may have a lot of shorted 6v LEDs but you only have one LED open, Yes, only one chance, one of your LEDs is open, see if you can find out which one?

TV has no backlight, I found one led open by visual method then I shorted this led, TV backlights lighted up, i add more leds (any) to close to power supply led driver voltage, that's all.

Khufu's secret II......adding LEDs.
https://www.badcaps.net/forum/showthread.php?t=74702

[budm]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

Hopefully the PCB foot print will match your replacement LED, the replacement LED has large heat transfer pad as Cathode.
The ratings of the LED are OK.
http://www.lextar.com/?sn=90&lang=en-US&c=774

[link626]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

so when those LED specs are 350-700mA

If the TV only supplies 290mA when plugged in, that will still run?

[budm]

Re: How do I find exact replacement LED bead for this backlight strip? and will it la

Since we do not have details spec of the LED, the 350 mA rating may be the maximum current rating at 25c, the 750 mA may be the pulse peak current.
You do not want to run the device at maximum spec, you also need to do good thermal management. You always want to have safety margin when operating the device.
The 290 mA you measured may not be the maximum current the LED driver power supply is putting out since you do not know what the backlights setting is at for your TV right now, it may be at max, or 90%, 80%, who knows.
Look at example of the spec sheet.
BTW, looking at your pictures in your post 16, I cannot tell how the strips are wired up together, each strip had 4-pin connector, so it has 4 wires on each connector? The LED's have to connected in series some how.