Hisense 50K360G

[dbier63]

Re: Hisense 50K360G

lookimback: I measured voltage last night and have 206 Vdc on both legs of LED backlight.

whatusername: thanks for the offer but this tv is just too nice for me to give up on just yet.

[lookimback]

Re: Hisense 50K360G

Thank you dbier63. Now I know I have a problem with the power supply, as opposed to a bad LED.

[dbier63]

Re: Hisense 50K360G

So I changed the main and Tcon boards but still no picture. I guess I'm gonna pull the trim off and look at the panel.. Any suggestions would be greatly appreciated.

Thanks

[lookimback]

Re: Hisense 50K360G

I think that's your next move. Once you get the trim off, you might see the problem. It's sounding like TAB bond failure.

[dbier63]

Re: Hisense 50K360G

Ya know I am still getting a flashing code before led's power on. Blinks 7 times and a very short pause then 3 more blinks. Then the power supply turns on the led array. Can anyone tell me what this code string relates to? Could it mean the problem is with the panel?

[lookimback]

Re: Hisense 50K360G

I couldn't find a service manual for it. I doubt anyone will know what that code is.

[dbier63]

Re: Hisense 50K360G

I thought as much. I'm sure Hisense has some sort of schematic. They produced the piece of junk!
Anyway if I can't get it fixed. I'll just sell all the components I guess.

[lookimback]

Re: Hisense 50K360G

They make these things with the expectation of them being disposable, and not repairable.

[ecking767]

Re: Hisense 50K360G

So I changed the main and Tcon boards but still no picture. I guess I'm gonna pull the trim off and look at the panel.. Any suggestions would be greatly appreciated.

Thanks

did you find any problem with the LCD screen?

[lookimback]

Re: Hisense 50K360G

I played around with mine a bit more and realized that to force the backlights on, I needed to connect stby to SW and BRI. I knew that, but wasn't thinking. So my power supply is fine. Glad I didn't spend any money yet. Mine has to be the main board, and I'm leaning towards the eeprom. ShopJimmy has it and I'm going to give it a shot.

[dbier63]

Re: Hisense 50K360G

So I disassembled the panel and found no damage on the panel or backlight at all.
I inspected the ribbons connecting the panel to the address boards and found no damage there either. I'm guessing maybe one of the address boards has a surface mount cap issue. Can anyone direct me with testing the tiny caps on these boards?
I will post some pictures

[dbier63]

Re: Hisense 50K360G

lookimback: can you tell me what a tab bond failure is? Is it the connection where the ribbon is connected to the panel? If so I do not see any imperfections whatsoever. I'm telling you this panel looks brand new. I inspected it with magnifying glasses.

[lookimback]

Re: Hisense 50K360G

The panel is attached to the address boards by a process called tape automated bonding, TAB bonding for short. There is also an IC attached to the tape by a similar method. Sometimes the IC shorts, and that usually results in physical damage which you can see, i.e., the tab having a burnt trace. More commonly, the bond between the tab and the panel, IC, or address board fails. Personally, I think it's usually the bond between the IC and tab which fails. I've tried inspecting one under a USB microscope, but couldn't identify the location of the fault. Thinking about it, I may have had address board issues on that one but I didn't check for that. Generally, you can press on the tabs on the affected side and sometimes make the picture come back momentarily. On some TVs, you will have to cycle power while pressing on the tab. I generally slide my finger across the part where the IC is. If that doesn't have any effect, then press each one and cycle power. It helps if you have a little block of rubber or something to put behind the IC, just something so you can put a little pressure on it without stressing other bonding points.

[dbier63]

Re: Hisense 50K360G

Thanks for the info. I tried all the tests you spoke of but no change. What I do not understand is that when I only connect the right side ribbon from the tcon right side comes on. I've tried swapping ribbons from right to left of the tcon and different combinations but the only time the right side will come on is when right side is connected and the left isn't. I don't get it. Shouldn't i be able to hook up the working side ribbon to either port on the tcon to test it?
Maybe I still have a bad tcon?

[dbier63]

Re: Hisense 50K360G

Here is the screen with the left side driver board disconnected from the tcon.

[lookimback]

Re: Hisense 50K360G

You originally had a shorted Tcon right?

[lookimback]

Re: Hisense 50K360G

I would start with checking for continuity across each component. Do that with the TV off, unplugged. You only need to check the side which doesn't display an image. You will want to be very careful with those tabs. It doesn't take much to tear one. If you have a table or something, I'd lay it flat to work on it.

And no, you wouldn't be able to hook up the working side ribbon to the other side of the Tcon because the pinout would not be the same.

[dbier63]

Re: Hisense 50K360G

Ok thank you. So I want to check continuity on surface caps and resistors on the driver board on the side that doesn't work? Correct?

[lookimback]

Re: Hisense 50K360G

So I want to check continuity on surface caps and resistors on the driver board on the side that doesn't work? Correct?

Yes, and you will check the transistors too. Without removing the components it would be difficult to check them for the correct resistance, capacitance, etc., so the first thing is just to look for ones which may be shorted. Transistors should be checked with diode test mode, and in all 6 possible pin combinations.

Another thing you could do is try to find which trace supplies voltage to each individual tab and see if you could cut off that supply by removing a cap or resistor which is in series. With the bad side disconnected, you could probe the good side to figure out which trace provides supply voltage to the tab. The idea would be to shut down each tab until you get partial picture back on the affected side. I don't know for certain if that would work, but it's worth a shot.

[dbier63]

Re: Hisense 50K360G

I originally had a burnt IC on the Tcon board. Also can you tell me why I still get the flashing code when the driver board is disconnected? Is it a code locked in on the main board?