Sharp Aquos lc-60le831u question about LED's

[DXseekerMO]

Grabbed this Sharp Aquos lc-60le831u today. It had the 400ms followed by 1600ms flashing logo. Seller tried to force on with input/volume down but no luck. It's in real good shape otherwise.

Got it back to the shop, opened it up, checked voltages to find only standby 5.2. Did some research and found the right procedure to force the TV on which is volume down, channel up and power simultaneously pressed. It forced on with no backlights and voltage trailing off at the backlight connector and 3.26v on the error line.

Tried doing the flashlight test but it was too bright where it's setting, but if I leave it plugged in I can power it on and off with the remote and no force-on

As it got darker outside (tv is by a window) I hit power while looking at the screen (it's upside down on a table, second try, flashlight test) and saw something light up on the screen, thought it said HDMI and it looked like the backlights flashed on for a sec. Sure enough I look through the back of the panel and when I turn it off then back on the backlights come on for a second and go off.

Based on the brightness behind the screen (or apparent lack thereof) I'm thinking there's some bad LED's in there. I still have to do one more test, that is short one capacitor on the main board (the one on the error detect circuit) and see if the backlights stay on. If they do, bad LED's, if not then it's the power supply.

The problem is the number location I have for the cap is from a different set, a Sharp LC32. That cap is near IC7501 and is C7558.

So for my set I'm wondering which IC and cap do I need to be looking for on my main board so I can short that nearby cap and try to ice the problem down? Secondly, where can I buy new LED's for this?

[DXseekerMO]

Re: Sharp Aquos lc-60le831u question about LED's

Interesting observation. When I unhook and check voltage at C7211 (plug out to LED's, pins 1 and 3) and turn the set on with the remote the volts jump to 202 then trail off about a second later, but when I turn it off the volts increase to 104V and trails off shortly thereafter.

Why would the volts on the LED connector increase on shut-down? That seems a bit odd?

[budm]

Re: Sharp Aquos lc-60le831u question about LED's

Can we see the pictures of both side of the power supply/LED driver board?
Also need to see how many wires there are on the LED connectors.
The Voltage will jump up high if it does not see the load so the protection circuit kicks in and turn off the Voltage booster circuit.

[DXseekerMO]

Re: Sharp Aquos lc-60le831u question about LED's

Sure thing, here's pix of both sides of the power supply. I took close-ups of the backlight inverter area on both sides and a picture of the plug for the back light.

I checked voltages at each pair of wires. They all come up to 202v or so, except for the blue wire and the tan to its immediate right, it only seems to come up to 178V or so.

[budm]

Re: Sharp Aquos lc-60le831u question about LED's

OK, you have 4 set of LED strings:
LED 1+ (Anode)
LED 1 - (Cathode)

LED 2+ (Anode)
LED 2 - (Cathode)

LED 3+ (Anode)
LED 3 - (Cathode)

LED 4+ (Anode)
LED 4 - (Cathode)

So what do you have on EACH pin every time you turn on the TV?
1) TV off.
2) Keep Black probe on the chassis, then red probe on each pin at a time then keep an eye on the meter to see how high the Voltage jumps up to when TV is turned on and then wait 5 seconds to see how low it goes down to.
3) Turn TV off.
4) Move red probe to other pin and repeat step 2 and 3, and so on for the rest of the pins.
5) Report the readings.

[DXseekerMO]

Re: Sharp Aquos lc-60le831u question about LED's

I checked voltages at each pair of wires. They all come up to 202v or so, except for the blue wire and the tan to its immediate right, it only seems to come up to 178V or so.

Are these the voltages? I had the probes on the + and - of each pair, not on chassis ground.

[budm]

Re: Sharp Aquos lc-60le831u question about LED's

All 8 pins must be checked with ref. to chassis GND.

[DXseekerMO]

Re: Sharp Aquos lc-60le831u question about LED's

Is this done to check for voltage on the ground line?

I need to explain these readings to you. The positive side of all of these were rock solid over three tries. The negative side volts varied every time. That's why there's one positive and three negative volt readings. I find the varied negative voltage interesting because there seems to be no rhyme or reason.

LED1 + 201

LED1 - 146 34.6 1

LED2 + 201

LED2 - 37 17.4 49

LED3 + 202

LED3 - 75 138 33.7

LED4 + 202

LED4 - 37 11.2 7.5

[budm]

Re: Sharp Aquos lc-60le831u question about LED's

LED set # 1 and #3 look suspicious, especially on #1 looks like it may have some shorted LEDs. LED tester will sure come in handy since it will show the Vf (forward Voltage on each set of the LED strings then you can really compared the readings.
One way to find out too is to swap the LED # 1 pair to see if the reading will follow or not, same for set # 3.
All the L+ pins for the Anode of each LED strings are tied together and fed by the LED power supply.
The (-) pins are the Cathode return lines for the LED strings, each one with its own return circuit.

[DXseekerMO]

Re: Sharp Aquos lc-60le831u question about LED's

And with the connector hooked up......

L1 + 199
L1 - 91 94 97
L2 + 198
L2 - 101 113 108
L3 + 198
L3 - 113 93 101
L4 + 199
L4 - 94 96 93

Knew I should have asked that.

[nomoresonys]

Re: Sharp Aquos lc-60le831u question about LED's

https://www.ebay.com/itm/SID-GJ2B-0-...EAAOSw-URZsgm7 Backlight tester, lowest price I saw on ebay, 25 bucks item located in California.

[ljintexas]

Re: Sharp Aquos lc-60le831u question about LED's

http://www.lcd-chip.com

BEST I HAVE FOUND FOR LED ARRAY REPLACEMENTS. DID AN LG 47" 3D FOR $60 DELIVERED TO MY DOOR FROM CHINA IN ONE WEEK.COMPLETE WITH LENSES

[nomoresonys]

Re: Sharp Aquos lc-60le831u question about LED's

https://www.youtube.com/watch?v=mkoUe6e1f_A Simple do it yourself led tester, no readout just tester.

[nomoresonys]

Re: Sharp Aquos lc-60le831u question about LED's

http://www.lcd-chip.com

BEST I HAVE FOUND FOR LED ARRAY REPLACEMENTS. DID AN LG 47" 3D FOR $60 DELIVERED TO MY DOOR FROM CHINA IN ONE WEEK.COMPLETE WITH LENSES

Nice, they take paypal too.

[DXseekerMO]

Re: Sharp Aquos lc-60le831u question about LED's

Thanks for the link! I will have a look tonight.

Budm, what do you think of the voltages I posted with the backlight connector hooked up? Still think I have bad LED's?

[budm]

Re: Sharp Aquos lc-60le831u question about LED's

The L- are range from 91V to 113V, that is the big range, I do not know how many LEDs are on each string so without having meter that can show Vf of each string it will be difficult to know what the normal Vf should be.

[DXseekerMO]

Re: Sharp Aquos lc-60le831u question about LED's

I think two are 80led and two are 30 or 36led

[budm]

Re: Sharp Aquos lc-60le831u question about LED's

You will have look up the LCD panel spec sheet to find out if it will give the LED spec or not.
Two LED strip with 80 LEDs will require about 250V at 300mA, so I doubt that it uses 80-LED string, may be 50-LED string.

[zdsh07p9]

Re: Sharp Aquos lc-60le831u question about LED's

I have 3 of the original LED strips on ebay if you need them. Either that or I could part them out

[DXseekerMO]

Re: Sharp Aquos lc-60le831u question about LED's

I have 3 of the original LED strips on ebay if you need them. Either that or I could part them out

Can you post some pix of those in here, also could you tell me how many LED's on each strip? The best info I have is two have less leds and two have more? How many strips in that TV, 4?

Thanks for letting me know you have those.