Backlight Tester procurement

[captainKKK]

Please choose between these two LED testers, and reason of your preference. Thanks

Number 1:
https://www.aliexpress.com/item/1005003908772726.html
Input Voltage: AC85V-265V
Output Voltage: 0-320V
Output current:0-35mA

or

Number 2:
[url]https://www.aliexpress.com/item/1005002687350880.html
Input Voltage: AC85V-265V
Output Voltage: 0-300V
Output current:40-60mA

[sam_sam_sam]

Me personally I would want one that you can adjust the current more important than the voltage but do not get me wrong the voltage is also important as well if you can adjust the voltage and current you have the best of both worlds

I am not a real fan of automatic voltage/current self adjustable devices

I have one of these led back light testers and I personally do not like using it because it claims that it is automatically adjusts it self but it can not do single LEDs either so it not much use to me

I prefer to use an 0 to 80 volt adjustable voltage that has a 0 to 3 amp current limit switching power supply for this purpose but that just me

But you are asking for me to pick one it would be the first one but the description of the second one says 0 to 30 milliamperes but you have it as 40 to 60 milliamperes unless I read it wrong

[captainKKK]

Thanks Sam, from your criteria, I found this one, but it's only 0-230 volts, and may only work with 220 v AC? https://m.aliexpress.com/item/400026...mend-recommend

Or

https://m.aliexpress.com/item/329951...mend-recommend

Or, watch video on this one...seems to have more function:
https://m.aliexpress.com/item/329951...mend-recommend

[captainKKK]

Found and purchased this one. Hope all is ok. https://www.ebay.com/itm/202442894494

[captainKKK]

Nothing here

[sam_sam_sam]

Originally Posted by captainKKK

Nothing here

Thank you for posting this one this is somewhat what I have been looking for

This is okay however it is semi automatic / automatic it might be better than the one i have now

[captainKKK]

Originally Posted by sam_sam_sam

Thank you for posting this one this is somewhat what I have been looking for

This is okay however it is semi automatic / automatic it might be better than the one i have now

Maybe this one is for you:
https://www.aliexpress.com/item/3285...mend-recommend

[captainKKK]

I wonder, the seller raised the price from my $35.99 to $45.99, since yesterday. Aliexpress, Amazon uses cookies to raise prices and now I am wondering about EBay.....?? For this one, it States: "Note: The current adjustment switch is disabled during the test. It does not have the protection of a ramp-up voltage, it can damage your LED bead. You can stop the test area to adjust it." But not a problem, as start low, if not lit, cease lead contact, increase current....Maybe a little tedious, but I can at least use this for other tests.

[captainKKK]

https://www.ebay.com/itm/202442894494

[dellxps15]

i have repaired till now 6 tv with backlight problem. one was lg and was much easier to replace whole led kit for like 50€ because diffuser never get glued back well again and the others was able to replace just 1-2 led. in any of that repair i never had the need to use a led tester. each led stripe had positive and negative, so my lab psu was more then enought for them...

[clearchris]

Don't these leds have pretty similar rated life? Seems like something where you would want to replace them all while you had it out...

[captainKKK]

Originally Posted by clearchris

Don't these leds have pretty similar rated life? Seems like something where you would want to replace them all while you had it out...

Maybe, probably. But I use them to tell IF the BL are working when I have a "dead" set. There is no use for me to troublshoot the PS or MB if the BL are out or the screen is broken. If so, then I might test the PS voltages and strip the boards for resale.

The tester I bought has the capability to also test the BL driver so this just saved me lots of time on my last when the driver board and BL were good. A "dead" set ended up being fixed for a $0.14 schottky diode replacement. The "PROS" may have lots of test gear and a varible DC power supply they can test the BL with but I still like my dedicated BL tester.

[redwire]

I'm seeing where 1/4 of the backlight LED's are damaged, what happens is a cascade failure where one LED goes open/blinking and the PSU overdrives the other strips and damages those LEDs.
So you have to power up a strip and tap and poke to flush out the weak LED's and if you miss one you have to repeat the disassemble/glue/assembly thing again.

Are you seeing that, it's not one or two bad LED's but a bunch are in terrible shape so it's best to swap out the entire strip.

[captainKKK]

What do you think of this procedure beginning at 4:40 of THIS?

Although I got good test results testing a 65" set, I am quite sure if the number of leds per circuit get too many, the tester will not be able to drive them at full brightness.

[sam_sam_sam]

Originally Posted by captainKKK

What do you think of this procedure beginning at 4:40 of THIS?

Although I got good test results testing a 65" set, I am quite sure if the number of leds per circuit get too many, the tester will not be able to drive them at full brightness.

Thank you for posting this link How To Use This Device has convenient me to buy one for testing LED strips but I would use different hookup wires for testing different styles of connectors

[redwire]

The difficult part is LED's going intermittent. Blinking and cutting out - this is due to heating causing expansion and an open-circuit (in the cracked die, or bonding wires, or substrate glue) after which the LED then cools off and the connection is made again. Blink blink blink.

I haven't done the math how many watts is a typical LCD TV backlight, but testing at low currents does not always make enough heat in them to flush out bad connections in the LED. So people tap them, or use a heat gun to stress them.

I don't know how many watts that LED backlight tester can put out. They said 30-300VDC at 1mA or adjustable to 50mA? I don't see it putting out 15W.

[captainKKK]

Backlight LED Testing Methods
Default factory setting: Output Voltage 330V, Output Current 30mA. You can test the backlight of TV with any size at this default settings.
1. Self-testing: Plug in, turn the power switch on. The voltage is around 330V, current is 0; Contact the probes together, voltage changes to 0 and current changes to around 50mA, then testing can be started.
2. In testing:
Voltage = ‘0’, SHORT CIRCUIT.
Voltage = ‘330V’, OPEN CIRCUIT.
3. Testing single LED bead (Set voltage around to 20V and the current switch to 1mA):
A. With right polarity: the voltage shows on the tester of a normal LED bead is about 80% of the rated voltage, for example, the operating voltage of the LED bead is 2.4V if its rated voltage is 3V;
B. With wrong polarity: Voltage display the open circuit voltage.
4. Testing LED strips: Set the voltage to around 200V, change the current if need adjust brightness.
Introductions of the Additional Function
Voltage Test of Electrolytic capacitor:
Connect the black pen with the cathode of the electrolytic capacitor and the red pen with the anode. The voltage value displayed in the voltmeter will rise fast at the beginning. When reaching a certain point, the rising velocity will slow noticeably. At this time the voltage value displayed is the actual withstand voltage of the tested electrolytic capacitor. (The capacitors are qualified if the actual voltage value is higher than the indicated voltage value )
Notice: Avoid to break the capacitor, the testing time should not be too long.
1. Set the voltage around 20V and the current to 1mA when testing the voltage references of diodes, triodes, MOS tube and IC.
2. Set the voltage around 330V and the current to 1mA when testing the breakdown voltage of capacitors, stabilivolts, piezoresistors and TVS.

I have NOT tried the capacitor tests in this published LED tester guide.