Sharp LC-50LB370U Where to buy LED Strips?

[Gorrillasnot]

Re: Sharp LC-50LB370U Where to buy LED Strips?

Here are some pics with the tape removed from the wiring.

thanks

[budm]

Re: Sharp LC-50LB370U Where to buy LED Strips?

OK, I mark connectors 'A', 'B', and 'C' for you to test, we will test the LED string one at a time to see what you get.
1) Leave connector 'A' in place only then power up the TV and then turn on the TV to see if you can see the BACKLIGHTS set 'A' will come on for seconds or not.

2) Leave connector 'B' in place only then power up the TV and then turn on the TV to see if you can see the BACKLIGHTS set 'B' will come on for seconds or not.

3) Leave connector 'C' in place only then power up the TV and then turn on the TV to see if you can see the BACKLIGHTS set 'C' will come on for seconds or not.

[Gorrillasnot]

Re: Sharp LC-50LB370U Where to buy LED Strips?

When you say leave connector A in place do you mean disconnect all the other LED strings leaving only #1 and #2 plugged in?

Or do you mean place red lead of DMM on + of string 1 (black to chassis ground)? and then skip down to + of String 3 and so on?

I took readings from your locations you marked (with all strings plugged in) and I get 0v powered off, 38.6v initial power on then jumps to 69.3v then settles back at 38.6v and it lights up strip #2 although very dim.

Same thing happens when testing B.

When testing C (Strip #5) there is 0v in standby and 0v when powered on and strip #6 does not light up at all.

[budm]

Re: Sharp LC-50LB370U Where to buy LED Strips?

I mark the location of the three connectors: one at location 'A', another one at location 'B', and last one at location 'C'. We are dealing with just 3 connectors only at 3 locations, the rest of the connectors that I did not mark the location will stay in place.

So on the first test you leave the connector on location 'A' in place, remove the connector on location 'B' and at location 'C' then turn on the TV and see what happen.

Second test will have connector at location 'B' back in place and remove the connector on location 'A', 'C' is already not in place, then turn on the TV and see what happen..

Third test you will have connector at location 'C' back in place and remove connector on location 'B', 'A' is not already in place, then turn on the TV and see what happen..

Basically we are testing each LED string (each string contains 2 strips of LED connected in series) one at a time to see which one will not come on for seconds when you turn on the TV.

[Gorrillasnot]

Re: Sharp LC-50LB370U Where to buy LED Strips?

I see what you mean now..sorry for the confusion.

I get no flashes or signs of any LEDs lighting up.

Just to be sure I did the testing right..With all the strips plugged in except for B and C ( strip #3 and #5 unplugged) turn on the TV. No LEDs flash or light at all.

Plug B back in with A and C unplugged..again nothing lights up.

With B and A unplugged nothing happens at C.

The power light blinks 7 times red then turns to blue, but none of the LEDs flash or otherwise light up.

Also I wonder what is causing no voltage going to strip 5? I think that is what the problem is, but I don't know how to trace it down.

I have another question..if the wiring is damaged somehow to strip #5 could I disconnect it and jump from strip #6 positive to strip #5 negative and strip#6 negative back to strip #5 positive? (see pic)

thanks

[budm]

Re: Sharp LC-50LB370U Where to buy LED Strips?

You should see the Voltage on each terminal pin where the red wire attached to the connector at location 'A', 'B', and 'C'.
We know hat you have at least one bad LED on each string of the LED and you replace them in post 10..
At this point you will have to test each strip of the LED (1 LED string contain two strips of LED, and each strip of LED contain two small strips that are connected together with the connector in the middle.
So each strip has 11 LED then you will need power supply that can put out 33V at about 50mA testing current.
You can use four 9V battery connected in series and then add a 56~100 Ohm in series to test each LED strip (11 LEDs per strip).

[Gorrillasnot]

Re: Sharp LC-50LB370U Where to buy LED Strips?

I only have two 9v batteries on hand at the moment so I figured I could test 6 LEDs at a time including spanning the middle connector on each string..All LEDs work.
Just encase I'm missing something vital for the LEDs to work all that is hooked up on the TV right now is the PSU with a cable going to the LEDs and a cable going to the main board, and then there is a ribbon cable going from the main board to the T-Con and the power button is also hooked up.

that's all that's required correct?

I'm at a loss..I don't know what I am missing..if the voltages are correct and no LEDs are out then I don't understand why this thing still has no backlights.

BTW post #13 shows pics of what I have hooked up (last pic) and also the voltages I measured.
https://www.badcaps.net/forum/showpo...9&postcount=13

thanks

[budm]

Re: Sharp LC-50LB370U Where to buy LED Strips?

With the TV plugged in and powered on testing at the + at the head end of each strip I get the following voltage (from the top strip down)
1. 38.6v and causes the strip below it (strip 2) to dimly light all 11 LEDs.
2. 65.4v
3. 38.6v and causes strip 4 to dimly light up.
4. 64.4v
5. 0v there's a problem here somewhere, but not sure what..each bulb lights individually when checked with DMM in diode mode.
6. 65.4v

I think I'm getting closer..whatever is causing strip 5 to have 0v is probably the main problem?

thanks

What is not making sense is that you do get dimly lit LED when probing with the meter. We also know that something is bad on #5.
BTW, the 65.4V reading is ref to the chassis GND? I exepct it to be about 10~20V higher Voltage. With 22 LEDs per 1 LED string the total Vf will be about 66V at full current drive.

[Gorrillasnot]

Re: Sharp LC-50LB370U Where to buy LED Strips?

Yes the 65.4v was measured using chassis GND.

Since all the LEDs in strip #5 work (individually with DMM and 6 at a time with 2 batteries) are you thinking maybe something in the PSU is not right?

I'm not ready to give up just yet, but while I'm thinking about it I thought I'd ask..as a plan B last resort if I cant get the backlights to work as they should would it be possible/cost effective to power them via an external source of some kind?


thanks

[budm]

Re: Sharp LC-50LB370U Where to buy LED Strips?

"LED Connector.
+VLED2 = 65.4v standby. power on and it spikes to 96.4v then settles back down to 65.4v
+VLED1 = Same as above."

I went back and read the post, the output did go up to 96V before dropping down due to no load . At that much Voltage, the LED should all light up and you should see Voltage on the Black return wires. The Voltage reading on the strip has to be done with the probes connected before the TV is turn on, if you put the probes on after the TV is turned on then you only see the feeding Voltage of 65.4V that fed into the Voltage boost converter to boost that Voltage up over 70V.
Do you have 470 Ohms resistor?

[Gorrillasnot]

Re: Sharp LC-50LB370U Where to buy LED Strips?

I don't get any voltage on the black return wires (where the 2 black wires go into the connector) as seen in the pic on post #29 https://www.badcaps.net/forum/showpo...5&postcount=29


I don't think I have any 470s. I have some in the 300s and some 820k (leftovers from previous TV repairs)..If I could Identify them I have some junk TV boards and a few PC motherboards..maybe I could harvest 1.

[budm]

Re: Sharp LC-50LB370U Where to buy LED Strips?

300 Ohms will be fine for really quick test.
What you will do is to connect one end of the resistor to the chassis GND, another end will be connected to the pin (-VLED 2) of the LED connector that has black wire connected to it, then turn on the TV and you should see one of the LED string lights up, then turn off the TV.

[Gorrillasnot]

Re: Sharp LC-50LB370U Where to buy LED Strips?

My eyes are getting bad it wasn't 300 ohms but 390k.

anyways how is the end of the LED grounded (the end of the strip)?
I think that could be my problem..Strip #6 had a bad LED on the very end and I tried to remove it with my heat gun and I did remove it but it was bridged and I didn't have any solder wick so I cut the strip off where the last LED is and soldered a replacement piece in place..I will show a pic when I get a chance.

Anyways I went from chassis ground to the - of the very end LED on 6 and powered on the TV..Strip 6 lit up but none of the others did..


thanks

[mmartell]

Re: Sharp LC-50LB370U Where to buy LED Strips?

You cut off the return wire by cutting the strip. The last led has a track leading back to the socket so it can go on to power the next strip.

At least that's what I think you're saying though it still doesn't account for why the other strips aren't lighting up.

How exactly did you wire the last led maybe you damaged your power supply ?

[mmartell]

Re: Sharp LC-50LB370U Where to buy LED Strips?

Run a temporary wire from the last led (-) to the black wire at the connector and remove the resistor. The bottom two strips should light up at least temporarily if the power supply is good.

[mmartell]

Re: Sharp LC-50LB370U Where to buy LED Strips?

I don't want to step on budm toes maybe wait for him to chime back in. In the meantime post a pic of how you wired in the last led.

[budm]

Re: Sharp LC-50LB370U Where to buy LED Strips?

You have to follow the #52, that test will light up just string of the LED, the test will tell me if you have open circuit in that LED string or not, no need to cut or disconnected any connector.
The LED returns go through the two IC's to GND on the board, So with the resistor in place we are letting the return current flowing through the resistor to GND.

[Gorrillasnot]

Re: Sharp LC-50LB370U Where to buy LED Strips?

Took me a while , but I finally got the TV working.

mmartell: I used your suggestion and ran a ground wire from the last LED to the negative of the connector at the other end of the string and BINGO she worked.

I also want to thank budm..you knowledge is invaluable.

Thanks also to Reeceyburger..I used your stacking video on youtube as a guide.

thanks to everyone else who has given help/advice.

I still have a problem though. I think I mixed up the diffuser sheets..I should have taped them together in the corners with masking tape, but I didnt and they slipped apart when I was moving them.

Anyway I now have white circles in the video (see attached pic)..If I recall there was 1 thick frosted white sheet 1 or 2 thin frosted white sheets and 1 or 2 thin clear sheets..Anybody know the proper order for diffuser sheets from the bare chassis to just before the LCD screen?

Thanks

[budm]

Re: Sharp LC-50LB370U Where to buy LED Strips?

"mmartell: I used your suggestion and ran a ground wire from the last LED to the negative of the connector at the other end of the string and BINGO she worked." I do not quite understand what you did. I thought all the connections from the LED connector on the power supply board tested good all the way to the LED strings connectors.

[mmartell]

Re: Sharp LC-50LB370U Where to buy LED Strips?

Post #53 bud, he cut off the strip before the last led not realizing he would have also cut the return path for the entire string.