Digihome (Vestel) LED Backlighting Problem
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Re: Digihome (Vestel) LED Backlighting Problem
TV failed last week. Switch on, fine, but screen goes blank after a couple of minutes. Restarting the TV fixes the problem but it keeps recurring.
Sometimes the left half of the screen only goes dark and the right half stays bright, before the whole thing fails.
Dismantled TV, done lots of checking of LED bulbs, voltages at various different points, etc. but I'm struggling to make sense of it. Don't think LEDs are all faulty on one side of the screen (3 individual bulbs have failed on the other side of the screen but it doesn't stop the others working). Can't find any broken connections - everything seems intact.Last edited by bigalxyz; 08-21-2016, 11:41 AM.Comment
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Re: Digihome (Vestel) LED Backlighting Problem
The two and a half strips that work - voltage drop across each bulb is 2.4 - 2.5V, nice steady bright light.
The two and a half strips that don't work - voltage drop across each bulb is ALSO 2.4 - 2.5V, but they just barely light up. Not only that, but they stay in their just barely lit up state when I put the TV in standby mode!Comment
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Re: Digihome (Vestel) LED Backlighting Problem
Those LEDs are set like Christmas lights. Did you follow Reeceys suggestion about bridging? LED's can fail different ways. Open, short, or fail when they get hot. Maybe there is a bad solder joint somewhere, who knows. You may swap some strips around if it is possible. Maybe a connector could be lose or bad connection etc.Last edited by CapLeaker; 08-21-2016, 01:37 PM.Comment
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Re: Digihome (Vestel) LED Backlighting Problem
Those LEDs are set like Christmas lights. Did you follow Reeceys suggestion about bridging? LED's can fail different ways. Open, short, or fail when they get hot. Maybe there is a bad solder joint somewhere, who knows. You may swap some strips around if it is possible. Maybe a connector could be lose or bad connection etc.Comment
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Re: Digihome (Vestel) LED Backlighting Problem
yours way to test LED wrong. sorry.. as CL wrote before LED are currents not voltage. this mean, each LED had one Ziner Diode bulit in at opposite way, so you need to turn off the TV and each LED with yours test metter als Diode make the measurement,, each LED give you measure in Diode way resistances less than 50 its bad and drain currents. shortet mean will be zero and DMM will peep onComment
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Re: Digihome (Vestel) LED Backlighting Problem
yours way to test LED wrong. sorry.. as CL wrote before LED are currents not voltage. this mean, each LED had one Ziner Diode bulit in at opposite way, so you need to turn off the TV and each LED with yours test metter als Diode make the measurement,, each LED give you measure in Diode way resistances less than 50 its bad and drain currents. shortet mean will be zero and DMM will peep onComment
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Re: Digihome (Vestel) LED Backlighting Problem
don't give attention on if they light up or not in this stage.. just focus on the Diode way.. you have one line good, take the measurement of one LED as references to compare with other dimm or off one.Comment
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Re: Digihome (Vestel) LED Backlighting Problem
I've quickly tested now. In diode modes the good LEDs (the ones that I've seen light up with my 7.2V battery) show numbers of about 1050. However two of the bad ones give numbers of 100 or 200. And one of the other LEDs shows "1" on the screen which I think means an open circuit, so presumably infinite resistance, no complete circuit and no current flowing?
The bit I don't understand is that I got these numbers by reversing the leads on the multimeter, so that the "ground" lead on the meter (black) was connected to the + side of the LED, and the "live" lead on the meter (red) was connected to the - side of the LED. I hadn't expected this. But I don't get any numbers if I swap the leads around, just "1" (open circuit) every time.Last edited by bigalxyz; 08-21-2016, 02:25 PM.Comment
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Re: Digihome (Vestel) LED Backlighting Problem
Im out.Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !
https://www.facebook.com/Telford-Tel...7894576335359/Comment
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Re: Digihome (Vestel) LED Backlighting Problem
the diode test should be done not via the black or red or brown... you should scratch the line of each LED to test direct on the LED self.
mean the diode test of led should not as groupr or double.. must be each led alone.Last edited by Diah; 08-21-2016, 02:41 PM.Comment
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Re: Digihome (Vestel) LED Backlighting Problem
Yes, that's what I did - I scratched through the surface of the strips before and after each LED so that there is a little bit of copper underneath.Comment
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Re: Digihome (Vestel) LED Backlighting Problem
No, very consistent for the good LEDs, all very close to 1050. So I have to assume that's the "correct" number.
As I said, I saw 100 from one of the dead LEDs, 200 from another one, and open circuit (infinite resistance) from another.Comment
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