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Old 11-09-2018, 12:06 PM   #1
Rickig
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Default 42ls5600 backlight

Have a 42Ē LG edge lit tv that has a backlight issue
Tv comes on lights and sound for 3-4 seconds then back light shuts off.
I have 24v out to Led driver board. 3.5v to inverter on.
On the red wire with back light on I have 115v which drops to 24v when backlight goes out.
8.8v on 3 of the black wires when lights on which if the light stays on long enough goes to 20v drop to 0.7ish when off. The other 3rd from right goes to about 1.5v but if light stays on long enough goes to 14v.
The light has just come on and stayed on, have 20v on those 3 and 14v on the other still.
Would this indicate a bad led strip or driver? I donít come across many problems with the edge lit led strips.
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Last edited by Rickig; 11-09-2018 at 12:07 PM..
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Old 11-09-2018, 12:30 PM   #2
Andrew F. Ali
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Default Re: 42ls5600 backlight

Go into the settings and turn down the backlight setting to 20 if it is at 100 or 80. and see if that helps.
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Old 11-10-2018, 03:57 AM   #3
Rickig
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Default Re: 42ls5600 backlight

Yes I’ve just dropped to 20 and the light stays on.
The voltages on the led driver black cables have all gone up to 27ish volts except the one that was lower, that’s sat at 22v (they increases the lower the back light setting. Assume that these are returning voltage and are being monitored by the driver and if ones lower than the minimum it shuts off)

Slowly increase back to 100 and eventually the voltage drops to under 1v on that bank and it shuts off, The other 3 hover around 9v so assuming the led array has 4 banks of leds sharing the same common but with separate grounds and one bank is consuming too much power and as such shutting the driver off when on 100%.

So is it safe to say that the led array is faulty?
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Old 11-10-2018, 09:37 AM   #4
Andrew F. Ali
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Default Re: 42ls5600 backlight

Yes that is correct.
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Old 11-10-2018, 10:13 AM   #5
Rickig
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Default Re: 42ls5600 backlight

I’ve remove d the led array, found a replacement new on Ali express for under £20 so have ordered that.

Found one Led not illuminating when I put voltage on it on the bank that’s dropping voltage so aaaume it’s that one thats bad but already ordered the array so will wait.
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Old 11-10-2018, 10:59 AM   #6
Andrew F. Ali
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Default Re: 42ls5600 backlight

I've found in a lot of cases with edge-lit backlights it is just one bad LED that causes the problem and mostly a LED nearer to the connector. Hardly one in the middle.
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