On the second picture the LED in right has something black. do you think that`s faulty diode or not?

Can i test somehow these strips out of the TV - what voltage to use and where to apply?

thanks

 

Have you tried googling the part numbers you can read on it? You might be able to find specs for it.

 

at first page in google results i see nothing usefull about the working voltage.

If you can tell me something it will be good. Maybe to test the diodes one by one somehow or power the entire board with 11 LEDS...

 

Have you tried decoding the QRcode? (could be a Data Matrix code, though).

 

Yes. My camera cannot identify it. Maybe the camera of my Lenovo is not good enough.

The idea asking here is TV technicians to see and help. I find the product in Google but this parameter is not listed. Listed are for example physical lengths

 

Not surprising, most only do QR codes. If you have an iPhone, this supposedly will decode Data Matrix Codes. There may be an android equivalent.

 

very funny but not for me.

I was before minutes with my colleges of pawn shop and Iphone and Samsung couldn`t identify absolutely nothing

 

Try a better picture with indirect lighting and no flash. Zoom in on it, then post it.

 

Hello,

I tried a OCR reader on my tablet and it only gave me a number:
21GB27U1R33BU1R33C0605
To me it looks like a production code.

Bertus

 

So...

The problem at all is in inverter like you said or in the led backlights?

The idea is to test these boards(the two backlights) out of curcuits and see they are lighting or not. What value can this voltage be?!

The one i did is to replace all(except one) EC on the board with power plug. The one capacitor haven`t replaced is purchased from AliExpress.

If i can make some check on diodes transistors you could make a advice.

 

I can at least confirm "21GB27U1R33BU1R33C0605" from the data matrix also.

It does look, however, as though the first LED in the strip (from the power connector) is blown. Likely this is a series string of LEDs, so it follows that a blown LED would put them all out of circuit.

 

Perhaps helpful. Perhaps not.

However, a replacement LED strip *can* be found here:

https://www.ebay.com/itm/SONY-LED-STRIP-32WBVG56-TIS-4A-94V-0-1405-KDL32R420B-/301640660557

 

OK...an approach to determining the power supply voltage:

Count the number of LEDs in the affected strip. Multiply that by 3.3V. You can test each strip, as a whole, by supplying it with that particular voltage, provided that you also take the step of using a current limiting resistor.

Examine the power distribution circuitry to determine if multiple strips are wired in series or parallel--I suspect the former, frankly.

If parallel, the supply voltage = 3.3V * [number of LEDs in strip]

If series, the supply voltage = 3.3V * [sum of the number of LEDs in all strips]

You can scratch the white top coat off above the traces on each strip--in small, localized patches--and test each LED with a 3.6V Lithium cell, and a 100Ω resistor to limit current. When done with the testing, just touch-up the top coat with some white paint or white correction fluid....whatever you have on hand that matches the color and reflective characteristics.

Hopefully, this will speed the process of repairing this monitor/TV.

 

hm.

the point is i see no voltage to power these LEDs.
I did some blind checks on resistances and diodes on the top side of the board. Have replaced all electrolytic capacitors except one which i just put out and have measured(it`s ok)

I put out the elements on the heat sinks. The doubled diode is OK and before minutes have open thread in this forum about the MOSFET >>
https://forum.allaboutcircuits.com/posts/1203608/

Help and ideas will be good accepted

 

The service file for power board is called
vestel_17ips11-r4_psu_sch

I cannot really find where to look for curcuit supplying voltage for backlight

EDIT Ohh the mistake for N time was mine but i found it logically. When measure the voltage have used 20V scale thinking the volgate would be low than 20 V. When transform to 200V scale i see the voltage and then it`s going under without 2*Led strips connected

 

Common problem for these LEDs to go bad. If you hook about 25V to the strip (pay attention to the polarity markings on the end plug), it'll light up if good. Individual LEDs can be tested as earlier described, with a battery & resistor. Some TVs will only put out voltage to the backlight for a moment, then shut down if they detect an improper load. Shopjimmy is a great source for TV parts, including LED strips, just go to their website & punch in the TV model number. If you get it fixed, then you go into the TV menu and drop the backlight brightness value down a bit. Some LG TVs even have an update that does this. If you can't get replacement strips, # LATWT470RELZK LED (from AliExpress) is one that has fit most of the TVs I've dealt with. Had to swap polarity on a couple of them, though, due to a LED pad size mismatch. Used JB weld to glue the diffuser lens back on. Takes practice to get the new LED soldered in properly. Due to the work involved in taking the display assembly apart & putting it back together, and the likelyhood that more LEDs will soon fail, I replace all the backlight LEDs at the same time.