Hisense H50N5300UK reboots when showing full red images

[Track4207]

Hi all! A bit of an interesting and unusual problem: as the the title suggests I have a Hisense H50N5300UK that reboots when showing fullscreen solid red images (and some other solid colours, but red generally causes the issue the fastest). I first came across the problem assuming it was an intermittent issue, but later lucked into finding out that a title sequence of a show I watch happened to trigger the reboot.

What happens:

• TV appears to operate normally, for an indefinite amount of time until a problem image appears
• The problem image is displayed very briefly, then the display turns off, including the backlight
• Power light begins flashing
• TV boots normally, including showing the Hisense boot logo animation
• TV starts normally and resumes showing previous source
• TV continues operating normally until another problem image attempts to be displayed

Here is a summary of my findings so far:

• The reboot does not occur when showing a fullscreen solid Green, Blue or White images.
• The reboot can be triggered by solid colours like Yellow and Magenta.
• It seems that the reboot is triggered at around ~83% intensity when doing a ramp of a solid Red
• - At lower intensities it takes more time for the reboot to occur, after ~87% the reboot occurs near instantly
• I can reproduce this on all of the HDMI inputs.
• I can reproduce this using the test patterns built into the service mode of the TV itself.
• It is possible to work around the problem (at least at 1080p60) by reducing the saturation, brightness and contrast in the image settings.
• - The TV can operate indefinitely like this, it's successfully stayed on for over 7 hours straight without issue, but obviously the image isn't great.
• Higher resolutions seem to trigger (2160p60 tested) a near instant reboot, regardless of image being shown, but because it's so fast I can't do much experimenting
• Otherwise the TV works normally

I have tried the following in an attempt repair this problem:

• Replaced all the electrolytic caps on the main power supply board (mostly out of crossed fingers more than anything else): reboots still occur
• Heated up both the main mother board and power supply with a hair dryer separately: I could not trigger a reboot with the heat
• Measured the voltages on the TCON board:
• * VGH_1 = 26.3V
• * VGL1 = -7.7V
• * VDDAMR1 = 8.6V
• * V33D_1 = 3.28V
• * V18D_1 = 1.49V
• * VIN_1 = 12.02V
• * VIN12_1 = 11.99V
• * V33V_1 = 3.29V
• * V18V_1 = 1.49V
• * VDDC_1 = 0.93V
• * V0V95_1 = 0.95V
• * MEMC_2V5_1 = 2.5V
• * VDDAL = 17.59V
• * VCM_TFT_1 = 7.27V
• * VCM_CF_1 = 7.27V

Here's some further information the TV:

• TV make and model: Hisense H50N5300UK
• Power supply model: RSAG7.820.6666/ROH
• Motherboard model: RSAG7.820.7454/ROH
• Panel make and model: Innolux V500DJ6-QE1 Rev. T1
• TCON board labelling: EATDJ6E11

I'm honestly not quite sure where to go from here! Any help would be massively appreciated on where I should start looking next.

Cheers!

[notallbad]

Re: Hisense H50N5300UK reboots when showing full red images

Hi
what I would suggest is that you try turning the backlight (not brightness) to maximum in settings, go on youtube and search 'white screen' and see if this causes your fault symptoms and if it occurs sooner.

[Diah]

Re: Hisense H50N5300UK reboots when showing full red images

log in service menu and go to option clear chips,,, this is hard reset of the tv

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

Hi
what I would suggest is that you try turning the backlight (not brightness) to maximum in settings, go on youtube and search 'white screen' and see if this causes your fault symptoms and if it occurs sooner.

Hi there! Thanks for the suggestion, it seems that it still reboots regardless of backlight level and doesn't seem to be triggered any faster or slower.

It still doesn't reboot when showing full white though, only when showing a full red image. Not entirely sure why it only happens when it's red isolated by itself, or when showing solid magenta or yellow, but not white.

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

log in service menu and go to option clear chips,,, this is hard reset of the tv

Thanks for the reply!

I just gave that a go, unfortunately the behaviour still persists. Out of curiosity, is there a difference between the service menu ‘Clear chips' and the reset to factory defaults available in the standard menus?

[Diah]

Re: Hisense H50N5300UK reboots when showing full red images

Thanks for the reply!

I just gave that a go, unfortunately the behaviour still persists. Out of curiosity, is there a difference between the service menu ‘Clear chips' and the reset to factory defaults available in the standard menus?

factory default its just reset user setting.... clear chips from service menu are hard reset ( roil back the firmware )

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

factory default its just reset user setting.... clear chips from service menu are hard reset ( roil back the firmware )

Ahh that's great to know, thanks for the clarification!

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

An unexpected update:

To rule out whether a problem was localised to one side of the panel, I disconnected the right hand side (left hand connector when viewed from the rear) from the TCON board and then ran the test patterns that previously caused the TV to reboot. With the right hand side disconnected the TV displayed the test patterns without issue.

I plugged the right hand side of the panel back in and re-ran the test patterns and the TV still didn't reboot. This leaves me to suspect that the issue may have been related to a connection issue between the TCON and the panel itself, I presume some contamination on the connector. I have disconnected and reconnected these previously though, so I do have some doubts about this potential conclusion.

At the moment everything seems to be working normally, all of the previous configurations that could cause an instant reboot now no longer do so. I'm hesitant to cause it truly ‘fixed' until I've had it work for a few weeks without issue.

[Diah]

Re: Hisense H50N5300UK reboots when showing full red images

An unexpected update:

To rule out whether a problem was localised to one side of the panel

years ago i got Hisense UHD, it go to boot loop when switching only on Sat Channel Nasa UHD.. only on this channel boot loop, i should disconnect the SAT LNB cable from TV then it no boor loop so i can switch it to other channel..
contact Hisense Eng. and they dont have any explain... but it was firmware... when i downgrade it to early Version... it work perfect on this channel and others. .. not strange yours issue this why i suggust clean chip. so try to downgrade.

mean while it could be the resolution of yours test file... check it... you have in Service menu also RGB pattern

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

Quick further follow up, it's proven to be nothing related to those cables, it's back to rebooting when showing the test patterns.

years ago i got Hisense UHD, it go to boot loop when switching only on Sat Channel Nasa UHD.. only on this channel boot loop, i should disconnect the SAT LNB cable from TV then it no boor loop so i can switch it to other channel..
contact Hisense Eng. and they dont have any explain... but it was firmware... when i downgrade it to early Version... it work perfect on this channel and others. .. not strange yours issue this why i suggust clean chip. so try to downgrade.

mean while it could be the resolution of yours test file... check it... you have in Service menu also RGB pattern

Unfortunately the ‘clean chips' command in the service menu has had no effect and the issue remains, it did successfully roll back the firmware though. The reboot can be caused by the test patterns in the service menu too.

I'm struggling to think of a reason why the TV only reboots when showing particular images/colors. I can make it reboot instantly when showing certain images from any source, including using the test patterns in the service menu. It's particularly strange.

[notallbad]

Re: Hisense H50N5300UK reboots when showing full red images

will the tv power on with the tcon disconnected? albeit with no picture

Can you connect an external source with the test pattern that causes the reboot to see if the tv will stay on or not.

if it stays on next try it with the tcon connected but the panel disconnected, try the test again. results?

This will possibly eliminate the main and tcon and possibly prove its the panel.

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

Not sure actually, I’ll give that a go.

I can certainly start it and use it normally with half of the panel disconnected from the tcon, I’ll try disconnecting the both sides of the panel, but leave the LVDS connected and see what happens. Then I’ll see if it’ll attempt to operate normally with even the LVDS disconnected from the tcon.

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

will the tv power on with the tcon disconnected? albeit with no picture

Can you connect an external source with the test pattern that causes the reboot to see if the tv will stay on or not.

if it stays on next try it with the tcon connected but the panel disconnected, try the test again. results?

This will possibly eliminate the main and tcon and possibly prove its the panel.

Following this up, here are the results:

• Disconnecting LVDS cable from main board to TCON = TV stays on as expected
• Reconnecting LVDS cable from main board to TCON, with panel still connected to TCON = TV reboots
• Disconnecting left panel cable from TCON = TV stays on as expected
• Disconnecting right panel cable from TCON = TV stays on as expected
• Disconnecting both left and right panel cable from TCON = TV stays on as expected
• Reconnecting both left and right panel cable from TCON = TV reboots

I tested the above in the following two ways for each test:

• Memorising the remote inputs to trigger the problem test pattern from the service menu (showing a full red display). This was easy to confirm was working when half the display was still visible as the working half would go red. I don't know for sure that was true when both sides of the panel or the TCON itself was completely disconnected.
• Plugging in a laptop outputting a 2160p60 image, with audio playing. I can confirm that the main board is working and the TV is not rebooting as I could hear audio playing from the TV itself. I can also see on the laptop that the main board correctly reports it's model numbers and video is being sent to the TV, even if it cannot be seen as the display is disconnected.

Throughout this experimentation I decided to measure some voltages and noted the following:

• During the reboot cycle, the 12VDC rail from the main power supply drops to ~2.94VDC quickly and then recovers back to 12.15VDC.
• Crudely measuring ripple on the 12VDC rail from the main power supply using a multimeter shows around ~0.037V ripple. When an image is finally shown on screen this rises up to ~0.064V before the reboot occurs. I don't know if this is even a valid or useful measurement though.
• During the reboot cycle, the 16VDC rail from the main power supply remains on constantly but rises from a stable 16.56VDC to 17.12VDC as the reboot happens. I presume this is just the rail becoming unloaded.

I'm not entirely sure what conclusion to come to from this testing. It sounds to me like the power supply is either going into some sort of protection on the 12VDC rail for what I'm presuming to be an over current situation, or it's failing to sustain the 12VDC rail and causing the reboot. I don't see how this can be triggered so repeatedly by either a solid red display or a high resolution input though. Does a solid red display cause the TCON to draw more power? I could certainly see how a higher resolution image could cause the TCON to draw more power at least. Either way, I'm honestly not sure.

Nothing on the TCON board is getting particularly warm (other than the main controller chip, which I presume is to be expected). A totally uneducated guess would be that something in the TCON is consuming more power than it should be for some reason. Any ideas at all?

Thanks again for the input.

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

A quick followup:

I have managed to get access to the schematics for both the power supply and the main board (if I'm allowed I can post them here).

With this new information I have found out the following:

• The 12V rail appears to be switched by the main board (this is the rail that seems to collapse when the reboot occurs), the 16V rail is always on.
• The power for the TCON (VCC-Panel) is switched by a mosfet on the main board, it's not powered directly from the 12V rail.
• When in standby the 12V rail seams to float around 10.38V, I'm not sure if that's to be expected. The rail doesn't go anywhere near as low as it does when has a problem reboot though.
• In the course of testing, I left the TV off for an hour or so while I inspected the boards, once re-powering the TV back up, it would still reboot when showing the red screen, but not instantly, it takes a few minutes for it to reboot first time around. After that first instance though, it'll reboot instantly when showing the screen.

A further totally uneducated guess is making me suspect the power supply more. If the main board was turning the panel off by choice, I presume it would use the mosfet in the VCC-Panel circuit to do so. However that's not what happens, it looks like the 12VS rail collapses down to a low voltage around 2.9V on the actual Power Supply end.

With all of this said though, I'm still not entirely sure where to go next. I feel like there may be a thermal component to the failure too, as evidenced by the failure not happening instantly when displaying problem image after the unit has been disconnected from mains power for a while. I suspect this problem hadn't been picked up during my hair dryer test as I had not realised the requirement for a problem image on screen or high resolution mode to be used (I presume to increase the current draw into the problematic range).

Any further guidance would be massively appreciated.

[Diah]

Re: Hisense H50N5300UK reboots when showing full red images

The 12V rail appears to be switched by the main board (this is the rail that seems to collapse when the reboot occurs), the 16V rail is always on.

the 12V rail read less in STB mode are correct to read less then it goes high after switch TV ON
i am interesting to see yours service menu photo at white balance to see the values of Gain and Offset and Panel

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

the 12V rail read less in STB mode are correct to read less then it goes high after switch TV ON
i am interesting to see yours service menu photo at white balance to see the values of Gain and Offset and Panel

Sure thing, please see photo attached.

[Diah]

Re: Hisense H50N5300UK reboots when showing full red images

bring back R GAIN to 128

after change and exist S menu... loh again S. menu and clear chip

[Track4207]

Re: Hisense H50N5300UK reboots when showing full red images

bring back R GAIN to 128

after change and exist S menu... loh again S. menu and clear chip

Can do. I reset the R GAIN back to 128 and then ran the ‘Clean Chip' command.

Unfortunately the TV still reboots showing red in the Pattern Test.

[Diah]

Re: Hisense H50N5300UK reboots when showing full red images

Can do. I reset the R GAIN back to 128 and then ran the ‘Clean Chip' command.

Unfortunately the TV still reboots showing red in the Pattern Test.

i dont think so... did you look at s,menu if r gain ready to 128 ?
i wrote t to change value then exit s,menu,,,, then after turn on log again see if change in place then clear chip

[Diah]

Re: Hisense H50N5300UK reboots when showing full red images

by way.. if you have ready backup of channel and system on USB stick... don't use it to bring back your old setting and channel... cause it will written back the R Gain value too