Sharp Aquos LC-60LE830U One Long One Short

[mmartell]

Re: Sharp Aquos LC-60LE830U One Long One Short

$39 now? the price is slowly coming down.

Yessir. And not from China either, California. Was wondering about something though...

Many edge lit led strips are actually two equal strips in parallel. If a single led opened in a strip (or in my case all four strips) would that cause a properly functioning power supply to shut down the backlight ? Because that creates the scenario where the backlight tester says "ok" but in reality they're not. This unit reported 108v for each of my strips. Shouldn't it be testing for current draw as well so the user can compare with the readings from other strips inside the panel since they can't really be seen ?

[dick_barton]

Re: Sharp Aquos LC-60LE830U One Long One Short

That's an interesting senario. The unit provides a variable voltage at what I believe is at a constant current. So I reckon testing a led string with one or more short circuited leds would display a lower voltage on the tester display.

[dick_barton]

Re: Sharp Aquos LC-60LE830U One Long One Short

Out of curiosity I have just checked mine. I put my multimeter in series with the positive terminal output probe and have the following results when testing.

Shorting the probes together, current = 29mA
Testing 1 Led, current = 29mA
Testing sting of 6 leds, current = 29mA

So it look as though the current is a constant and it's the voltage that changes.

[mmartell]

Re: Sharp Aquos LC-60LE830U One Long One Short

So it would be wise to compare the voltage readings if you have more than one strip. At least that will tell you if you have any shorted leds which may not be apparent with the screen intact.

[dick_barton]

Re: Sharp Aquos LC-60LE830U One Long One Short

You could use that method but the only problem is that I noticed that some led strips have more leds than in the next/previous strip in the row.

Looking at a Youtube video of a led repair yesterday which had 8 leds in one row 9 in the next, then 8, then 9. Was odd.

Edit
As a quick and cheerful way of testing the leds I think it does what it says even if it can't handle all posibile errors you may encounter. You'll gain that with experience in using it.

[Moreno83]

Re: Sharp Aquos LC-60LE830U One Long One Short

Just curious. Does the V led turn on for a while and then goes to the 2 blinks? Mine does that. It turns on and the white "V" led lights up...takes like 10 seconds and it then shuts off with the same blinks. Backlight does not turn on.

[budm]

Re: Sharp Aquos LC-60LE830U One Long One Short

Once you get that LED tester, one good thing is that Built-in Voltmeter to show the Vf (Forward Voltage) of the LED.
I.E.
You have two strips of LED, each strip has 4 LED.
When you connect the tester to one of the two strip you get the reading of 12V, but when testing the other strip you get 9V, it means that the one with 9V reading has one shorted out LED.

[dick_barton]

Re: Sharp Aquos LC-60LE830U One Long One Short

My thoughts were as an example if you were testing one led strip with 7 leds and a second strip with 8 leds but you are unaware of the number of leds per strip because you have not opened up the panel, then the voltage reading could mislead you.

[budm]

Re: Sharp Aquos LC-60LE830U One Long One Short

That is true if the the strips are not the same.
So the bad thing is that if you have one big string with 2~3 shorted out LEDS, the string will still light up using the tester but the LED driver circuit may go into over current shutdown due to shorted LEDs which is the condition I run into before. There is no way to be 100% sure unless you can actually get to the LED strips.

[mmartell]

Re: Sharp Aquos LC-60LE830U One Long One Short

Just curious. Does the V led turn on for a while and then goes to the 2 blinks? Mine does that. It turns on and the white "V" led lights up...takes like 10 seconds and it then shuts off with the same blinks. Backlight does not turn on.

No, mine starts with the error blink right away.

[mmartell]

Re: Sharp Aquos LC-60LE830U One Long One Short

That is true if the the strips are not the same.
So the bad thing is that if you have one big string with 2~3 shorted out LEDS, the string will still light up using the tester but the LED driver circuit may go into over current shutdown due to shorted LEDs which is the condition I run into before. There is no way to be 100% sure unless you can actually get to the LED strips.

Exactly this. In my case it seems these leds are wired such that half of a horizontal strip is in series with half of the adjacent vertical strip such that a corner at a time will light per pair of wires coming off the driver.

So that's 50/2 + 30/2 or 37 leds. My tester reads a voltage of 108v per string or 36 leds at 3v each. I could have one shorted led per string but impossible to know without Vf for these particular leds and it would probably be a coincidence to have one led shorted per string anyway.

Would 12v missing out of 444v be enough to trip the protection anyway ?

On a more practical note what pins need jumpered to force on this supply ? I know standby with pson but I'm not familiar with some of the other Sharp designations.

[Moreno83]

Re: Sharp Aquos LC-60LE830U One Long One Short

It took me 3 mainboards to turn this tv on! Other 2 mainboard the V led starts blinking right from the start and i only had 5V on the powerboard.

With this 3rd mainboard the tv turns "on" but i got bad led strips i think. Check my thread , it has pictures.

[mmartell]

Re: Sharp Aquos LC-60LE830U One Long One Short

Well I can put this one to bed.

After reading another Sharp thread here yesterday the poster implied to power on the set by plugging it in THEN push and hold the power/input/vol- buttons - so I did. After a few seconds the "V" stopped flashing and went solid, followed by a soft power supply "click" and the screen lit up with a "k" on the left hand side. Then a ch-/vol+ (or was it ch-/vol- ?) and the service menu was on the screen. I grabbed the remote and reset the Lamp Error by turning it to "On" then powered the set off with the remote and unplugged it. Been coming on normally ever since even after cycling the mains several times.

I will add that the capacitive button board nearly fell out of its slot so who knows if it was even pushed up tight against the bezel during my previous attempts. Will fix that before I button it up.