Hisense 65P8

[ruckusman]

Hi there,

I've got a Hisense 65P8 and it's stopped displaying a picture 6 months out of warranty.

Pictures attached
I've written out the codes on the stickers as they aren't very legible being so faint.

Power board: RASG7.820.7920 - HLL5066WJ



Main board: RSAG7.820.7969 - HA657700UWGT



T-con board - 55T36-C04 - TT-5565T50C17


I've been doing a lot of research and diagnosis.

Symptoms firstly:
Unit was working one evening, then the image became a set of wide coloured stripes, [not the thin lines some experience, more like a single horizontal line of pixels was brushed up the screen from the bottom]

So I waited a few minutes to see if if was a broadcast issue, tried displaying a menu - still coloured stripes.

Powered it down, unplugged, switched back on and backlights illuminate but there's nothing displayed.

The screen is essentially black [black as in the black of when it's on with the backlights on].
I should add, I have tried the flashlight method to check if anything is displayed, it' blank.

This isn't an uncommon fault, but reading as many Hisense threads as I can locate, there doesn't seem to be a good testing through to definitive fault diagnosis and successful outcome.

I've checked all of the power rails, as noted, backlights are illuminated, no picture, sound works.

There's 12V at the T-com board [fuse checks out] and I've tried the method of disconnecting each of the two t-con to panel connectors one at a time to see if I get one half of the display - I don't, the screen remains black.


Please correct me if I'm wrong, that suggests the panel isn't faulty or damaged, it's not receiving image data.

The T-con is functional electrically [fuse] chips warm when the unit is powered up.

So I've removed the heatsinks, as shown in the photos in preparation for reflowing the Novatek NT72334TBG graphics chip.

Is there anything else I can do to nail it down to the main board or t-con board before I do the reflow.

I don't want to do it just for the sake of it before exhausting all other possibilities.

thanks

Glenn

[viewerau]

Re: Hisense 65P8

Sounds very much like my dilemma...

https://www.badcaps.net/forum/showthread.php?t=116525

[ruckusman]

Re: Hisense 65P8

Sounds very much like my dilemma...

https://www.badcaps.net/forum/showthread.php?t=116525

It does indeed, my symptoms are a little different. no picture at all, but I have been following your thread with interest.

I just did this test as described in your thread and the screen stayed dark in my case

https://www.badcaps.net/forum/showpo...3&postcount=20

Now I need to understand what that means as a result

[Diah]

Re: Hisense 65P8

you need to take out the Bezel and inspect the LCD screen glass specially the corner if there any break

if its in good shape. have access to the buffer boards and check if you have on it U ribbon.. need to unplug one a time and check if you got picture3/4 screen

[ruckusman]

Re: Hisense 65P8

you need to take out the Bezel and inspect the LCD screen glass specially the corner if there any break

if its in good shape. have access to the buffer boards and check if you have on it U ribbon.. need to unplug one a time and check if you got picture3/4 screen

Thanks, I have checked all of the ribbons, both ends between the main board and the t-con and the t-con to buffer boards.

All are in perfect condition with no signs of burning or discolouration from excess current.

First:
I have done the test with removing 1/2 half of the t-con to buffer board ribbons, one side and then the next.
No change the screen stays dark on both sides with that test.

Second:
I have also done the test with the t-con LVDS cables disconnected from the main board and provided only 12 volts from the main board to the fuse on the t-con board.
No change, the screen stays dark.

I have also tested the voltages at all of the inductors on both the main board and t-con board - I will post photos with my results.
I have reasonable [expected] voltages at all inductors except for two on the t-con, which showed 4 millivolts - not zero volts, a very small voltage.

I will re-test those voltages with the t-con to buffer cables removed to see if there is a higher voltage on those two specific inductors on the t-con board.

I just removed the covers for the buffer boards to check the capacitors and have found this thread about TVS protection diodes also.

https://www.badcaps.net/forum/showthread.php?t=118339.

My screen looked very much like these when it failed at first.

There is also this thread about the TVS protection diodes.
https://www.badcaps.net/forum/showthread.php?t=118195

I will check the capacitors, resistors and protection diodes first on the buffer boards before removing anything.

thanks

Glenn

[Diah]

Re: Hisense 65P8

its wrong to test removing LVDS on the set. unless the stand alone test..
i asked if you have U ribbon cable on the buffer boards....

[ruckusman]

Re: Hisense 65P8

Yes I have ribbon cables connected to the buffer boards.

The panel is in perfect condition, it got put in place and has never been moved since it was first installed.
It has never been wet or had anyting spilt on it.
It's my TV so I know all of it's history.

Tests I have done:

First test:
Main board with both LVDS cables connected to t-con and one side of t-con U ribbon to buffer boards, each side separately.
Dark screen, no image both times on either side of the panel - no change.

Second test:
T-con standalone mode, LVDS cables unplugged between main board and t-con, both t-con to buffer U ribbon cables connected.
12 volts from main board supplied to t-con board.
No change, dark screen remains.

I am uncertain what the second test provides, if there is firmware on the t-con to show coloured red, green blue screens or should it remain dark?

[Diah]

Re: Hisense 65P8

Yes I have ribbon cables connected to the buffer boards.

U ribbon are flex cable like the U letter figure installed on the buffer boards ( mean each side of buffer boards will be 2 pieces connected with U

you are talking on the main ribbon cable between T-CON and panel..

so upload photos of yours buffer boards first

[ruckusman]

Re: Hisense 65P8

OK, now I understand what you mean by U cables.

I have removed the cover from one buffer board, I will take some photos and upload them once I have removed the second cover for access and photos.

Stay tuned...

[ruckusman]

Re: Hisense 65P8

Here are the 4 buffer board photos, visual inspection doesn't show any blown components.

I have circled the 4263H TVS diodes on both of the outer boards.









I will go through and check for any shorted capacitors or open circuit resistors

[Diah]

Re: Hisense 65P8

you have U ribbon... did you disconnect each side once and turn on ..to see if you have picture

[ruckusman]

Re: Hisense 65P8

Yes I have conducted that test as well as the standalone t-con test.

The screen remains darkened at all times, it does not display an image/picture

[Diah]

Re: Hisense 65P8

in this case.. if you have sound + the backlight come on + you have 12V on T-con F .. then replace T-CON

[ruckusman]

Re: Hisense 65P8

I've just run two further tests on the t-con:

One in both standalone mode and with the LVDS cables connected with the t-con to buffer ribbons cables connected alternately; and

One with the above with both t-con to buffer ribbon cables disconnected.

I was checking voltages at the inductors.

First test previously was with all cables connected and I got some strange voltage readings on some of the inductors, noted on the image.



Then the same check of the voltages with no ribbon cables connected between the t-con and the buffers.

I did actually do this with one side and then the other and then with no cables connected to the buffers, no difference between them.
Note the voltage differences on two of the inductors.



I will check across the buffer boards tomorrow for shorted components, something is not right with them.

[lotas]

Re: Hisense 65P8

This indicates that the panel or strips are in short or low resistance, current protection is triggered and these voltages are blocked.

[ruckusman]

Re: Hisense 65P8

This indicates that the panel or strips are in short or low resistance, current protection is triggered and these voltages are blocked.

Thanks lotas, I have been reading some of your other solutions to similar issues, especially this one with the TVS protection diodes

https://www.badcaps.net/forum/showthread.php?t=118195


I will check across the components of the buffer boards and remove the TVS diodes tomorrow

[Diah]

Re: Hisense 65P8

it make no sens to remove the ESD Diode.. you did before disconnect U ribbon. which it mean you already take out the ESD out of the circuit .

[ruckusman]

Re: Hisense 65P8

I haven't desoldered the ESD diodes yet as I don't want to just remove something before a thorough check and test.

Now I can see what you mean by the U ribbon, your description was clear, my vision and thinking was not, it was very late last night.

The U ribbon is this connection between the buffer boards.



I will test with the two U ribbons disconnected, the t-con LVDS cables connected and the t-con to buffer cables connected obviously.
Now I fully understand that test.

Some sort of success, I have done the u ribbon disconnected test and now have the centre portion of the screen showing a striped image, whereas it was only dark previously.



T-con voltage tests:
Also I did that extra test of the voltages at the inductors on the t-con board with no panel connections to compare with my first set of measurements which showed three abnormally low voltages on three inductors.

I have two voltages that were previously pulled low that without the t-con to buffer cables connected are now normal.

There is however one remaining voltage on the t-con which is still low with no connections, and only 12v volts applied directly to the t-con [standalone], which is essentially 0v at L204.

I haven't managed to locate the schematic for t-con 55T36-C04, that would make it easier to check.

At least now I will have a target of either short circuit or very low resistance components [capacitors] to search for on the buffer boards and the t-con.

[lotas]

Re: Hisense 65P8

There should be no voltage on L204, it stands on Gnd, this is to form a negative voltage (- XXv).

[ruckusman]

Re: Hisense 65P8

There should be no voltage on L204, it stands on Gnd, this is to form a negative voltage (- XXv).

Thanks for this tip, it saved me removing the t-con board again unnecessarily and spending time checking components when no problem existed.

SUCCESS
I have a working TV again.



The solution was the removal of D001 from BOTH outer buffer boards, please keep that in mind to understand the tests I conducted which follow.

Firstly checking the 4263H ESD diode on the outer buffer board revealed a short circuit on the pin labelled in the photo.



Note: This was the same for both components on each side.
I've also checked them once removed and that pin is still short to ground.

What may prove helpful for others is the sequential testing I conducted as follows:

I removed one 4263H diode first, then connected three quarters of the screen to test.

I had checked all of the other components on that first buffer board, before reconnecting the 3rd buffer board and obtaining the lines up the screen for the three quarters of the panel with the 4th buffer board u-cable disconnected.

Connecting the 4th buffer board whilst only one 4263H ESD diode was removed from the first buffer board did not display anything on the screen which was my original symptom.

So with that test conducted I moved to the other end and directly to checking then removing the other 4263H ESD diode.

Then connecting the 4th buffer displayed the correct image, the unit is fixed.

What I can say is that my unit wouldn't correctly display half of a screen at a time when alternately disconnecting either t-con or U-cables to the buffer boards.

Many thanks to lotas and Dinah for their time and suggestions