attempt to clone LED TV Backlight Tester

[budm]

Re: attempt to clone LED TV Backlight Tester

budm is it true that a shorted led can still light up? im sure ive read somewhere they can.

No, if it is shorted then it will be about the same as a piece of wire.

[vinceroger69]

Re: attempt to clone LED TV Backlight Tester

thats what i was thinking thanks for conformation and budm do you think that tester in the link is worth buying? ive just had a email back saying they will ship to the uk as i dont mind waiting a few weeks for it and i think the uk price will be a little cheaper than the ones shown on the web page

[budm]

Re: attempt to clone LED TV Backlight Tester

I would like to have one myself to really test how it react without load and with load. It is a good as long as it has good protection and no blowing up good LED when testing it afetr the unit is turned on and not connected to the load, that is what I am trying to understand how fast the circuit reacts as posted in post 59..

[vinceroger69]

Re: attempt to clone LED TV Backlight Tester

i think at that price £21.79 shipped too the uk i will take a chance.
Edit i have just payed for it so when it comes we can run some tests.

[capwizard]

Re: attempt to clone LED TV Backlight Tester

Any tricks in the payment because all the prices are too good to be true(some of items are $0.01)? Why dont they accept VISA?

Western Union (No Bank Fee) , but it is bank to bank transfers maybe charge $50
PayPal (PayPal Fee 5%) * Shippment address must match with PayPal register address
MoneyGram (No Bank Fee) ???
HSBC Bank (Bank Fee $25.00)
Alipay.com (Need to contact us) ???

[vinceroger69]

Re: attempt to clone LED TV Backlight Tester

How about Payment? They doesnt accept VISA?

Western Union (No Bank Fee) , but it is bank to bank transfers maybe charge $50
PayPal (PayPal Fee 5%) * Shippment address must match with PayPal register address
MoneyGram (No Bank Fee) ???
HSBC Bank (Bank Fee $25.00)
Alipay.com (Need to contact us) ???

I used paypal but he replied to my email within 10 minutes which was good when i asked about uk postage.

[budm]

Re: attempt to clone LED TV Backlight Tester

Any tricks in the payment because all the prices are too good to be true(some of items are $0.01)? Why dont they accept VISA?

Western Union (No Bank Fee) , but it is bank to bank transfers maybe charge $50
PayPal (PayPal Fee 5%) * Shippment address must match with PayPal register address
MoneyGram (No Bank Fee) ???
HSBC Bank (Bank Fee $25.00)
Alipay.com (Need to contact us) ???

Where do you see the fees?
https://www.hklrf.com/Payment_1.html
I use PAYPAL, so LRF will charge 5% fee and added that to the price?

It also show accept credit card on the right side of the page.
https://www.hklrf.com/0-300V-Smart-F...pair_1948.html

[vinceroger69]

Re: attempt to clone LED TV Backlight Tester

yes paypal charged me £1.00 i think but still a cheap tester at that price.

[capwizard]

Re: attempt to clone LED TV Backlight Tester

vinceroger69 : After you get it , Please let us know it is good or bad. Open it and take some pictures. Thank you.

[vinceroger69]

Re: attempt to clone LED TV Backlight Tester

vinceroger69 : After you get it , Please let us know it is good or bad. Open it and take some pictures. Thank you.

yes of course i will.

[rievax_60]

Re: attempt to clone LED TV Backlight Tester

I have traced some of the circuitry, it makes better sense now.
With the test leads open, the Source of Q1 rises to the point where the G-S drops to threshold voltage of about 2.5v. Q1's channel resistance will be very high.
When the leads are connected to a load, very little current first flows through Q1, the current increases as C8 charges. Q1 eventually ends up with about 3v drop across it.
The current limiting is done by an unidentified SMPS IC that I have represented by Q2.

[rickou]

Re: attempt to clone LED TV Backlight Tester

So I will tell how I test my LED strip from TV all strip at once without any tester. I have a old outlet cable that I took from a radio and I have cut and put 10kohm/2w resistor in series then I make one probe, in the other able i only have put one probe.

When I need to test LED from a TV I put the cable in a 230V outlet and test directly the strip not even have bother in see the plus and minus..

Here you have the most cheap, free of electronic waste, and reliable I use this for more then 4 years now

[rievax_60]

Re: attempt to clone LED TV Backlight Tester

So I will tell how I test my LED strip from TV all strip at once without any tester. I have a old outlet cable that I took from a radio and I have cut and put 10kohm/2w resistor in series then I make one probe, in the other able i only have put one probe.

When I need to test LED from a TV I put the cable in a 230V outlet and test directly the strip not even have bother in see the plus and minus..

Here you have the most cheap, free of electronic waste, and reliable I use this for more then 4 years now

That is too risky even for experienced people. It is not uncommon to find outlets with Active and Neutral transposed.
Have you tried using back to back transformers for isolation?

[budm]

Re: attempt to clone LED TV Backlight Tester

Yep, cheap, works, and dangerous. Max current worst case is 23mA.

[rievax_60]

Re: attempt to clone LED TV Backlight Tester

So I will tell how I test my LED strip from TV all strip at once without any tester. I have a old outlet cable that I took from a radio and I have cut and put 10kohm/2w resistor in series then I make one probe, in the other able i only have put one probe.

When I need to test LED from a TV I put the cable in a 230V outlet and test directly the strip not even have bother in see the plus and minus..

Here you have the most cheap, free of electronic waste, and reliable I use this for more then 4 years now

How do you test single or smaller groups of LEDs? Many LEDs do not have reverse protection diodes.

[budm]

Re: attempt to clone LED TV Backlight Tester

That is why I said it is also dangerous (to human and device) and good LED can be damaged, at least put 1n4007 in series and have to test with correct polarity. You can be lucky for so long.
https://www.digikey.com/en/articles/...ial-protection

[rickou]

Re: attempt to clone LED TV Backlight Tester

I can test only one led or more led's there is no problem. I don't need to see the polarity cause I'm applying AC voltage and this voltage will be rectified directly by the same leds that I'm testing. So I'm having half wave in the led thats why is irrelevant the polarity. The only thing is that the led will blin will blink 50times a sec here I live is 230v 50Hz but I can barely see this. I will post some pics if you want.

[budm]

Re: attempt to clone LED TV Backlight Tester

We are talking the reverse Voltage breakdown of the LED or any diode.
I know your setup, no need for pictures. Just look up what reverse breakdown Voltage of the diode is.
What do you think what the reverse Voltage is aplied across the LED when it is in reverse bias during the half cycle of the applied AC?
There is reason why minimum diode break down Voltage is chosen to be used in the circuits.

[rickou]

Re: attempt to clone LED TV Backlight Tester

I know what you are saying but when running this test I have 0.01A that is passing in the circuit is harmless, it is exactly the same principle as the light bulb in series to test power supply or any circuit that has a short.

[budm]

Re: attempt to clone LED TV Backlight Tester

"it is exactly the same principle as the light bulb in series to test power supply or any circuit that has a short." Really?