Hisense 50K20DG

[m4a2t0t]

No backlight

I'm getting 30 mV out of the top connector. I've seen a few threads about these and they all had burnt out back light strips.


Anyone have a schematic for the boards?

[budm]

Re: Hisense 50K20DG

No backlight

I'm getting 30 mV out of the top connector. I've seen a few threads about these and they all had burnt out back light strips.


Anyone have a schematic for the boards?

Which top connector? You have two of them on the top left of the board.
The connector that goes to the main board has pin labels for each pin so you MUST report the Voltage reading for each pin by putting down the pin name and then follow by the Voltage reading for each pin so we can easily see if they are normal or not.

But do you have indicator light, image on the screen, and sound?

[m4a2t0t]

Re: Hisense 50K20DG

The front indicator comes on and I can see the Hisense logo when I turn it off and shine a flashlight on the screen.

The 2 pin connector at the top is the one I tested at. I will go test the other connector and post the results.

EDIT:

If the top pin (BLK) is pin number one then all pins except 4 and 5 are at 0V, pins 4 and 5 are at 9.37V. No sure if it's useful info but the top 2 pin connector hits about 3.1V, right when it I turn it on, then goes to 0V.

[budm]

Re: Hisense 50K20DG

OK, so you also need to test the Voltage of both pins of the LED connector with reference to the chassis GND. Is that what you did when you are getting 30mV, ref. to chassis GND?
I also need straight shot pictures of the bottom side of that power supply board too.

[m4a2t0t]

Re: Hisense 50K20DG

At first I was just testing across the two pins. I tested again from chassis GND to each point. The left pins shows OL like I was reading resistance and the right reads 0.0V, if I change to mV on the DMM I can now see 3mV (it was 30mV yesterday) on the right pin and OL on the left.

[budm]

Re: Hisense 50K20DG

OL = over range.
You need to set you meter to at 200VDC scale.
So far it sounds like the Voltage supply to the LED Anode seems to be OK.
The Red wire should be for the Anode of the LED string and that is where the Boosted Voltage is fed to, the White wire should be for the Cathode return wire for the LED string and if the LED string has open circuit then you will not get Voltage on the White wire.

[m4a2t0t]

Re: Hisense 50K20DG

There was something wrong with my other meter. This is what i get on my new one.

19.17
19.17
0
3.4
12.43
12.43
4.1
3.9
0
0

Top connector Left pin 230-240 Right pin -107v

The light also blinks 8 times, if thats an error code. I didn't see that earlier

[budm]

Re: Hisense 50K20DG

"Top connector Left pin 230-240 Right pin -107v"
Which one is red and which one is white?
"-107" Is that MINUS 170V?
If you do have 240V on the red wire then you have open circuit in the LED string.

[m4a2t0t]

Re: Hisense 50K20DG

left wire is red and right is white.

I double checked and it is -107V

[budm]

Re: Hisense 50K20DG

OK, I trace the board and see why it is showing negative, so that looks to be normal.
So are you 100% sure that you are getting 0V if you measure between the red and the white wire with and without the LED connector in place.
At this point it looks like you do have open circuit in the LED string.

[m4a2t0t]

Re: Hisense 50K20DG

If I test across the terminals I get 330V with the connector connected or disconnected. Positive on DMM to red wire on connector, NEG to white.

[budm]

Re: Hisense 50K20DG

If I test across the terminals I get 330V with the connector connected or disconnected. Positive on DMM to red wire on connector, NEG to white.

That means the power supply is not seeing the load (LED strings).

[jackfish]

Re: Hisense 50K20DG

Bad leds..take it apart..I had same problem...

[m4a2t0t]

Re: Hisense 50K20DG

I guess I need a LED strip tester. Will this one work?

https://www.ebay.com/itm/110V-265V-L...8AAOSwiQ9ZR5x1

[budm]

Re: Hisense 50K20DG

That tester will work, but it only put out about 30mA instead of 100's of mA as in the circuit but at least the tester will tell you which LED is not lit.
Or you can use two 9V batteries connected in series to create 18V power supply and then connect that is series with 100 Ohms 1W resistor to start with power up one strip of LED ( one at a time to see which one is bad first.
Notes: Each strip has 6 LED so if they are 3V LED then you will need about 18V supply with test current limit of 50mA or so to start with.

[m4a2t0t]

Re: Hisense 50K20DG

One strip is completely dead and two more have 1-2 LEDs out.

Is it going to be a waste of my time buying used strips? Does anyone carry them new for a decent price? I see shopjimmy has them but I have to buy all 11 strips. Not even sure if they are new or repaired.

[Andrew F. Ali]

Re: Hisense 50K20DG

I see shopjimmy has them but I have to buy all 11 strips. Not even sure if they are new or repaired.

I have used Shopjimmy Parts and NEVER had an issue. I would recommend change-out of ALL the strips to be sure and prevent any 2nd guessing. If you want to fix your TV, once and for all.

[freakaftr8]

Re: Hisense 50K20DG

Shop Jimmy LED backlights I don't believe are ever repaired they are replacements from cracked screen TV's.

And yes I agree, never replace just a bad one if you had the option of replacing all of them.. These things are like tires when one is ready to pop the others aren't far behind

[m4a2t0t]

Re: Hisense 50K20DG

Changing all of them does seem better. Went ahead and ordered the set from shopjimmy

[budm]

Re: Hisense 50K20DG

One strip is completely dead and two more have 1-2 LEDs out.

Is it going to be a waste of my time buying used strips? Does anyone carry them new for a decent price? I see shopjimmy has them but I have to buy all 11 strips. Not even sure if they are new or repaired.

BTW, did you test them as I suggested?