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Old 02-15-2019, 07:58 AM   #1
capwizard
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Default Antique LED tester

I have a VARIAC variable transformer, I used to test on analog TV, now TVs are changing to switching power supplies, is kind of useless so I try to modify to CC-CV LED Tester can be used on the newer modern TV.

I know that it doesn't look good, look like a shirt, but I hope someone can give me advice.

On the other side of the lid, I may not be able to find it. But don't worry about that I might use cardboard instead and good for ventilation.
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Last edited by capwizard; 02-15-2019 at 08:19 AM..
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Old 02-15-2019, 08:03 AM   #2
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Default Re: Antique LED tester

try to connect a stepper motor to the shaft.
then a microcontroller can regulate the voltage or current using feedback from an inductive sensor etc.
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Old 02-15-2019, 08:07 AM   #3
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Default Re: Antique LED tester

Thank you, my friend, but this is mainly for Africans. The simpler the easier, the better.
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Old 02-15-2019, 09:16 AM   #4
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Default Re: Antique LED tester

I opened it.

Pic5 Can someone breaks the codes. What are the letters mean? I hope it is not stolen from school or something!

I have a question? what is that 5 and 2 pins use for in this variac? Probably it will give out 80 v AC. Pic 6, 7
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Old 02-15-2019, 09:46 AM   #5
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Default Re: Antique LED tester

What letters? It is multi-tap Variac.
You still have to worry about safety since you are not isolated from the line.
Powerstat 21
https://www.alliedelec.com/product/s...c/21/70120679/
https://www.alliedelec.com/m/d/db9b7...41a87d906d.pdf
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Old 02-15-2019, 09:55 AM   #6
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Default Re: Antique LED tester

Thank you for your advice on safety issues.

What I'm going to do is I will put a Step-Down Transformer 120-30v reverse to step-up to 350v than diode to dc and add CC. Resolved a lot of people complained that led testers did not have enough current to test Increasing currents of tv backlight LEDs. (Now up to 500mA)

Last edited by capwizard; 02-15-2019 at 10:11 AM..
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Old 02-15-2019, 10:27 AM   #7
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Default Re: Antique LED tester

If you are going to be able to supply up to 350V @500mA , that is lots of power.
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Old 02-15-2019, 10:43 AM   #8
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Default Re: Antique LED tester

Quote:
Originally Posted by capwizard View Post
Thank you, my friend, but this is mainly for Africans. The simpler the easier, the better.
tie it to a small child to regulate the output.
or stop implying that africa is still 3rd world - much of it is better than some parts of the u.s. thanks to people like obama and his cinegog running the u.s. into the ground.
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Old 02-15-2019, 11:07 AM   #9
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Default Re: Antique LED tester

I have a dream..... but my dream was broken.

Everything was okay up to 150v but if I cranked up to 200-volt Transformer began to vibrate and eat up 1.2A this is a failure.

So I assumed this was not a very good transformer from the AC adapter so I changed very good stereo transformer but that was the same thing. It eats up about 3.7A.
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Old 02-15-2019, 11:42 AM   #10
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Default Re: Antique LED tester

i am not surprised,

but africa is 240v
so rectify it - 240 x 1.41 = 338.4v
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Old 02-15-2019, 12:29 PM   #11
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Default Re: Antique LED tester

African friends, I am coming. If we fail, don’t be discouraged. We believe we can fly.

Just like what sti suggested. We hook up AC direct to variac pins2,5 we have adjustable AC190v and we just test led strips with AC. Pic1 believe it or not leds do Walk on AC. Connected to a diode then you have a halfwave DC. you can use that to test leds.

Caution: this is live circuits like budm said. you either use groves or just solders pin on it before you test it, don't touch it with your hands.
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Last edited by capwizard; 02-15-2019 at 12:33 PM..
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Old 02-15-2019, 01:05 PM   #12
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Default Re: Antique LED tester

Some caution from LG about reverse bias (apply Voltage in reverse polarity) so be careful.
*1) Pulse width ≤ 10ms and duty cycle ≤ 10% ※ These values are provided for informational purposes only, not any warranty or quarantee. Regarding any kinds of warranty or guarantee, consult your sales representative.
※ Operating the LED beyond the listed maximum ratings may affect device reliability and cause permanent damage. These or any other conditions beyond those indicated under recommended operating conditions are not implied. The exposure to the absolute maximum rated conditions may affect device reliability.
※ The LEDs are not designed to be driven in reverse bias.
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Old 02-15-2019, 01:17 PM   #13
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Default Re: Antique LED tester

You said it is very correct, I just burned a lot of leds with AC, it depends on what kind of LED diodes leds used

This time I used one diode halfwave DC at 10ma, 50ma, 100ma. Pic1,2,3 Because of the low frequencies, the camera will have black strips on pictures.

One question is can I use the full bridge to rectify the AC voltage?
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Last edited by capwizard; 02-15-2019 at 01:28 PM..
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Old 02-15-2019, 01:28 PM   #14
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Default Re: Antique LED tester

So are you still using the transformer in reverse?
You can also use Voltage doubler/triple/... rectifier set up on the output.
You can also stack the windings (boost setup) to get 30VAC more output.
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Old 02-15-2019, 01:52 PM   #15
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Default Re: Antique LED tester

No i put one diode on it. Now I added one 474k capacitor the picture is ok now on 100ma.
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Old 02-15-2019, 03:36 PM   #16
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Default Re: Antique LED tester

I have one question is if I put two capacitors on both neutral and hot input lines is that means both AC lines are isolated and safe to touch?
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Old 02-15-2019, 03:38 PM   #17
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Default Re: Antique LED tester

Nope, current will still flow through the caps.
https://www.schneider-electric.com/en/faqs/FA157465/

Last edited by budm; 02-15-2019 at 03:41 PM..
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