Poorman's LED TV Backlight Tester.

[mariushm]

Re: Poorman's LED TV Backlight Tester.

400v at 10mA is 400 x 0.01 = 4w ... it's basically drawing more than 1A from 3.6v
Whatever battery you're using, it won't last long.

I don't like the idea of using CCFL drivers, those can place up to 1000-1500v on the output of the transformer. It's dangerous. The current should also be relatively low, a few mA at best (and they have current protections built in to protect the transformer from overheating)

[capwizard]

Re: Poorman's LED TV Backlight Tester.

1 or 2 18650

CCFL on a 9 Volt battery at 600 Volt output. Schematic diagram in description
https://www.youtube.com/watch?v=D_vSAP3nJcU

PS: Look this guy I don't think that potentiometer will last.

How to build a power supply to test LED strip for LED TV. Home made device. All brand.
https://www.youtube.com/watch?v=KxIwwXKmQP8

[cpt.charlie]

Re: Poorman's LED TV Backlight Tester.

O_o Not isolated from mains...... bad idea (but dirty cheap though).

[capwizard]

Re: Poorman's LED TV Backlight Tester.

dirty cheap ( muchísimas gracias, at that time my budget is $5), precise, and accurate..........I'm using it....everyday...For 3 months it never shocks me..... before..Yes, twice.......

EX: I test RCA LED55C55R120Q TV, I got 143v (pic3,4. Look at pic3 backlight is on). I know TV has 108 LEDs by pic5 ( This leds have no diodes protectors)

You can count the LEDs over here:
http://assets.shopjimmy.com/media/ca...8409b1-top.jpg................................

[budm]

Re: Poorman's LED TV Backlight Tester.

BTW, the full spec sheet of the LR8 IC was never provided.

[capwizard]

Re: Poorman's LED TV Backlight Tester.

Thank you , One question : Look the #24 pic3 LED testing voltage is 143.0 v, and pic4 is at 142.8 v.

Because of constant current source, so R=V / I means LEDS changing it resistance (went down) by the heat? Is this proved LEDs are non-linear and non-Ohmic loads?

attempt to clone LED TV Backlight Tester......Special thank to BUDM at #12. It makes this poormans LED tester came true.
https://www.badcaps.net/forum/showthread.php?t=55558

Now we know the heart of this tester is LR8, Actually they are using 2 of them another one is for 5v LED display directly from AC rectifier bridge.

PS: If anyone knows why this tester uses A big yellow film capacitor?

[cpt.charlie]

Re: Poorman's LED TV Backlight Tester.

Maybe it's the HV output capacitor (low capacity, high voltage).

[capwizard]

Re: Poorman's LED TV Backlight Tester.

For what purposes?

[budm]

Re: Poorman's LED TV Backlight Tester.

Vf of semiconductor is affect by temperature.


One application is using diode as temp. sensor.

[budm]

Re: Poorman's LED TV Backlight Tester.

For what purposes?

Yep, just a filter cap for that DC HIGH Voltage output to drive the LEDs.

[dobab]

Re: Poorman's LED TV Backlight Tester.

Poorman's LED TV Backlight Tester. use multimeter as voltage meter to saving $.

Finally working product: Add on type.

I use LR8K4-G IC , power use US AC 110v double to 220V. Current limit resistor use 270 Ohm.

Hello.Capacitor: C1=? ,C2=? Thanks.