Another LED Strip Head Scratcher.. Sanyo DP42D23

[Michale32086]

This seems to be my month for weird LED Strip issues..

I have this Sanyo that I broke down to the bare strips and discovered that the LED assembly is identical to some LGs and some VIZIOs I worked on..

I used my LED tester to find the bad strips and LEDs and was able to create an array that was fully functional.. No bad LEDs at all..

STILL wouldn't come on...

So I cracked open a 47" LED that had a bad display panel. At least I HOPE it did..

Anyways, long story short (too late!) I have confirmed that the following parts of the LED TV are fully function..

Power PCB

Main Video Board

ALL LED Strips

Cable that goes from the Power PCV to the Array board..

The "array board" (green strip that all the LED Strips plug into) seems to be the culprit.. But, near as I can tell, it's just traces and I can't find any breaks...

Voltages at the 4 pin connector on the array board are solid.. 200v at one testing....

I am thinking I need to check the voltages at the point where the LED Strips plug into the array board but I wanted to get guidance on what voltages should be present...

Thanx

FURTHER INFO: Regarding the pic, the upper array board is from the Sanyo and doesn't work. The lower array board is from the LG and it works fine.. It should also be noted that, lemme see if I can explain this right, the connectors that go from the Power PCB to the array board are inverted.. On the LG, the connector tab on both ends face the same way.. On the SANYO, the connector tabs are opposite..... If that makes any sense

[Michale32086]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

Here is what I mean about the Power PCB/Array connectors...

[budm]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

Can we see good clear pictures of the whole power supply/LED driver board?
The SANYO one: the black wires are more likely to be the Anode of the LED string, the white wires are the Cathode returns.

[tom66]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

I've encountered a set where every LED tests okay on a meter, but the whole setup fails for some reason. Perhaps an LED breaking down as voltage is applied or as it heats up. Odd, though.

[augiedoggy]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

I've encountered a set where every LED tests okay on a meter, but the whole setup fails for some reason. Perhaps an LED breaking down as voltage is applied or as it heats up. Odd, though.

Ive seen this too... sometimes Ive actually discovered it was just a cold solder joint on one of the leds..

[CapLeaker]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

LED's can work even for a while like it should and then go off. They can fail in a weird way and it is very hard to test unless you power the strip up properly on a CV/CC PSU and run it for a little while.

[budm]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

But he said "STILL wouldn't come on..." I would expect if the LED/LEDs is bad with high drive current then they should at least come on for seconds and then go off, according to the post, they did not come on.

[CapLeaker]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

Then maybe measure the LED string voltages at each of the strips and see if LED power actually gets there? Gotta be an open somewhere then.

[freakaftr8]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

I have supplied voltage to LED strips in different TV's especially LG, What normally happens is when I supply an external voltage to test LED strips, one led may light up on that strip however powered with the power supply on a much broader voltage range causing the LED to burn brighter starts to flicker

[budm]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

That is why it is important to use CC power supply to test the LED/LED strip due to the fact the if you have a bunch of shorted out LEDs on the strip then the good LED will be forced with lots of current trying to maintain the Vf when using CV power supply.
I.E. people see 4 LEDs on the strip so they figure that 4 LEDs x 3V =12V so he is going to use 12V to test the strip, but if two of the LEDs are shorted out then guess what happen when you apply 12V to the strip?

[Michale32086]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

Thanx for the replies, guys.. Turns out that it WAS a bad cable connector from the array board to the Power PCB...

Sorry it took so long to get back on it.. GRRRRRRRR I am NOT a holiday fan.. I would be happy to go from Oct 15 to Jan 16.....

Thanx again...

[budm]

Re: Another LED Strip Head Scratcher.. Sanyo DP42D23

Thanks for the follow-up.