Hisense 40K360MN dim picture like in power saving mode

[nortnil]

Hisene 40k360MN.

I am getting a dim picture. The TV will boot, and the panel will be full brightness for a split second before going dim. It is like it is in a power saving mode (picture below). I have seen the panel kick on all the way for a minute or two so I am guessing it is a power issue either from not enough power or something telling it to go into a power saving mode.

I have factory reset the TV, and adjusted all of the settings in the menu to see if something was a problem there. No luck on that end.

I did see a pin labeled "dimming in the power cord coming from the power supply to the main board. It is giving about 5.40v when powered on.

Visually I don't see any caps that look bad or any scorching on the power supply or the main board.

Below is a picture of the dim display and what the TV looks like with the back removed.

If anyone has any advice of what to try next, I would definitely appreciate it.













If you need better angles or close ups of certain areas let me know. Thank you.

[CapLeaker]

Re: Hisense 40K360MN dim picture like in power saving mode

So you are saying the backlight brightness is going low? What happens if you take the dimming pin out of the plug? TV should run on full backlight then. Another thought... did you do a factory default on the set yet?

[budm]

Re: Hisense 40K360MN dim picture like in power saving mode

Can you put the list of the pin names of those connector?
"I did see a pin labeled "dimming in the power cord coming from the power supply to the main board. It is giving about 5.40v when powered on." Did it go down after that or it stays at 5.40V? BTW, please check you meter's batteries, they may be low so it shows the reading higher than what it should be, the dimming max is 5V (5V = MAX brightness).

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

So you are saying the backlight brightness is going low? What happens if you take the dimming pin out of the plug? TV should run on full backlight then. Another thought... did you do a factory default on the set yet?

Yes, when the TV turns on for a split second it is at full brightness. Then the backlight drops down like it is in sleep mode. When I go to the image settings turning brightness and backlight all the way up do nothing.

The top right of the screen is also very dark. It looks like that LED is out entirely.

I just tried disconnecting the dimming pin and no picture would display.

[CapLeaker]

Re: Hisense 40K360MN dim picture like in power saving mode

Ok... can you measure voltages on all the pins on the power supply with name of the pins beside it and post it?

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

Can you put the list of the pin names of those connector?
"I did see a pin labeled "dimming in the power cord coming from the power supply to the main board. It is giving about 5.40v when powered on." Did it go down after that or it stays at 5.40V? BTW, please check you meter's batteries, they may be low so it shows the reading higher than what it should be, the dimming max is 5V (5V = MAX brightness).

You are right on the batteries. I will have to get a new one and post back with an update. In the meantime below are close ups of the connectors.

Power supply side


Main board side


I don't know if you need to know what cable matches what pin on each side, but just in case:
Power Supply to Logic Board
STB - Purple - On/Off
12V - Blue - Left 12VS
12V - Green - Right 12VS
SW - Yellow - BL
PWM - Orange - Dimming
GND - Red - Left GND
GND - Brown - Right GND

The last GND and the two 14V pins on the logic board are blank.

Ok... can you measure voltages on all the pins on the power supply with name of the pins beside it and post it?

I will have to get back to you on this tomorrow when I get a new battery for my volt meter.

[budm]

Re: Hisense 40K360MN dim picture like in power saving mode

"PWM - Orange - Dimming" OK it uses PWM dimming signal (10% pulse width = min brightness, 90% pulse width = max brightness), it is not using variable DC Analog dimming signal 0~5VDC.
If you check with DC meter and the pulse width is at 50%, then the meter should show 2.5V (50% of 5V).
So you need to check again what you have at that pin, if you remove that PWM dimming wire then then you should see full brightness.

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

"PWM - Orange - Dimming" OK it uses PWM dimming signal (10% pulse width = min brightness, 90% pulse width = max brightness), it is not using variable DC Analog dimming signal 0~5VDC.
If you check with DC meter and the pulse width is at 50%, then the meter should show 2.5V (50% of 5V).
So you need to check again what you have at that pin, if you remove that PWM dimming wire then then you should see full brightness.

I just replaced the battery in my meter and rechecked the voltages:
STB 4.96V
12V 12.08V
12V 12.08V
SW 3.37V
PWM 3.96

When I disconnect the PWM cable from the molex connect and power on the TV, I don't get any backlight at all.

There is also another cable coming off of the power supply going into the LCD panel frame. Does this have anything to do with the backlight?

Pins are labeled (voltages to the right):
V1P 0V
V1N -2.06V
V2P -2.06V
V2N 0V

Picture of the second connector to the right of the main connector:

[budm]

Re: Hisense 40K360MN dim picture like in power saving mode

"There is also another cable coming off of the power supply going into the LCD panel frame. Does this have anything to do with the backlight?

Pins are labeled (voltages to the right):
V1P 0V
V1N -2.06V
V2P -2.06V
V2N 0V"
That connector (with BLUE, BLACK, RED, AND WHITE) is for the LED strings inside the panel.
Are the Voltage readings on those using chassis as the GND ref for the meter/ If it is, the LED driver Voltage booster circuit is not working.
If it is working you should see >100VDC (measured right at the two legs of the caps) on filter caps C869, 859, 853, 909.
So see if the Voltage does jump up high when power switch is activated and stays high or if it jumps up high and then drops down.

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

That connector (with BLUE, BLACK, RED, AND WHITE) is for the LED strings inside the panel.
Are the Voltage readings on those using chassis as the GND ref for the meter/ If it is, the LED driver Voltage booster circuit is not working.
If it is working you should see >100VDC (measured right at the two legs of the caps) on filter caps C869, 859, 853, 909.
So see if the Voltage does jump up high when power switch is activated and stays high or if it jumps up high and then drops down.

Thank you for being so helpful.

I made a mistake with my meter and gave you bad information on the LED string connector. I didn't realize the power coming out was so high, and I had my meter set too low causing erroneous readings.

After correcting that I get these readings using the chassis as the GND
V1P 324VCD
V1N 0VCD
V2P 0VCD
V2N -139VCD

Do those look closer to where they should be?

As far as the caps the Voltage does jump high when power is activated and stay high.

I measured all of them using chassis as GND and then again across the pins themselves. All of them had the same value using chassis as GND and the negative lead as GND except for C869. It gave me 0VCD when using the chassis as GND

C896 138VCD (0VCD when using chassis)
C859 163VCD
C853 163VCD
C909 324VCD

I am still pretty green when it comes to taking readings and troubleshooting. If I am using the wrong terms or it sounds like I am doing something wrong, please let me know what I need to do to get you the right information.

Thanks again

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

I forgot to mention that during the power on for the split second the backlight is at full brightness C869, 859, and 853 all dropped to around 140VCD. I didn't notice a change on C909.

[budm]

Re: Hisense 40K360MN dim picture like in power saving mode

"C909 324VCD" That indicating you have open connection or LED/s in the string.
Similar problem to this one:
https://www.badcaps.net/forum/showthread.php?t=44541

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

Okay so that means it shouldn't be anything on the power supply then? I take it my next step is to try to disassemble the panel itself and see if there is anything I can do on the LED string?

[budm]

Re: Hisense 40K360MN dim picture like in power saving mode

Okay so that means it shouldn't be anything on the power supply then? I take it my next step is to try to disassemble the panel itself and see if there is anything I can do on the LED string?

Correct. Can you also post good clear the pictures of the bottom side of the board for me? I would like to see if the LED strings are connected in series or it has power supply per string.
The hard part will taking the panel apart without damaging the LCD Glass panel.

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

Will the 4th picture in my 1st post work? When you open it in a new window and zoom in it is pretty high resolution. If there is a certain area you need me to focus on I can try to get you isolated pictures tomorrow.

Or did you mean of the LED board when I get the panel open?

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

Deleted - duplicate

[budm]

Re: Hisense 40K360MN dim picture like in power saving mode

Bigger pictures (bottom side) of that area of the connector with RED/BLACK/BLUE/WHITE for the LED strings.

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

Will this picture work?

That was the closest I could get for everything to still be in focus. If you need something closer I can try to take segments and stitch them together for you. Just let me know.

I was also wondering about C869 having 0VCD when I measured using the chassis as ground. Is that normal, or could it indicate there is a fault breaking it's connection to ground?

[budm]

Re: Hisense 40K360MN dim picture like in power saving mode

" I was also wondering about C869 having 0VCD when I measured using the chassis as ground. Is that normal, or could it indicate there is a fault breaking it's connection to ground?" That is why I need really good pictures to trace out the connections.

[nortnil]

Re: Hisense 40K360MN dim picture like in power saving mode

Does that one work? It is 50 inches across at full resolution.