Vizio M70-C3 Dark Spots

[kentkirchner]

Re: Vizio M70-C3 Dark Spots

It was off, pictured left at calibrated for test, backlight=zero

[Diah]

Re: Vizio M70-C3 Dark Spots

Two pics on zero backlight, auto bright off

do the same test again of backlight level zero.. i thnk this auto brightiness was on... if it was off then no need to do it

i said the test with channel signal not jpeg or s other.. areal signal or cable signal of program that the picture will change and moved time to time

[kentkirchner]

Re: Vizio M70-C3 Dark Spots

i do wondering how you can remarkable the dark spots at back light level Zero.. you may have under picture setting some things like Auto Brightness Control.. this need to turn off.

please upload photos as other members request. now start the hard work

Two pics on zero backlight, auto bright off

[Diah]

Re: Vizio M70-C3 Dark Spots

OK, turned out the lights in the room and reduced the backlight to zero for 30 minutes. While watching, all dark spots are still noticable . Slowly increased the backlight from zero to 55, checking for spots while doing so and they remain on the screen

i do wondering how you can remarkable the dark spots at back light level Zero.. you may have under picture setting some things like Auto Brightness Control.. this need to turn off.

please upload photos as other members request. now start the hard work

[kentkirchner]

Re: Vizio M70-C3 Dark Spots

waiting on your response of the second test i suggest at post 22

OK, turned out the lights in the room and reduced the backlight to zero for 30 minutes. While watching, all dark spots are still noticable . Slowly increased the backlight from zero to 55, checking for spots while doing so and they remain on the screen

[Diah]

Re: Vizio M70-C3 Dark Spots

waiting on your response of the second test i suggest at post 22

[kentkirchner]

Re: Vizio M70-C3 Dark Spots

Sorry Diah, just saw your response above.

[kentkirchner]

Re: Vizio M70-C3 Dark Spots

on the specification of the this TV there are full arrow dimming system. as other said. this panel are big the risk to take out with one person do high.

reading voltage don't work at all as its currents to dimming or turn off. if there was one burned then whole back light will be out and TV will never start.
the rest we can think what i said before.. but its much we can know more close with easy steps

1- make hard reset from service menu and check result

2- attached UHD learning full arrow dimming system put them on fat32 usb format and play them on the tv one by one until you can see the white one full White.

if no change please report to do other test

Hello Diah, I restored the factory defaults and picture still the same. Next, I copied the black and white jpg's to a thumb drive and played them on a slide show for a couple minutes. I could always see the shadows when the white screen played.
Is that the tests you are asking for?
thank you,
Kent

[Diah]

Re: Vizio M70-C3 Dark Spots

Hello Diah, I restored the factory defaults and picture still the same. Next, I copied the black and white jpg's to a thumb drive and played them on a slide show for a couple minutes. I could always see the shadows when the white screen played.
Is that the tests you are asking for?
thank you,
Kent

Hard reset meant only the reset which done via Service menu. it roll back all driver and firmware to Factory condition. rest from user menu its just rest the setting of the user.

this test should be done with Cable or areal signal. not USB or HDMI signal.
please turn off the light of your room ( in case the TV set had build in Light room sensor ), and set the backlight level of the TV to Zero. keep it on and watching any things for at least 30 minute. then turn the backlight level setting to up slowly .. but not to full and check the dark spots at which level there no spots.

[budm]

Re: Vizio M70-C3 Dark Spots

:-) very wise on the "last thing to do" especially as a "first effort". Ultimately, I kind of doubt that to fix this set, there will be an easy / board solution.

I hate to see another broken panel.

[budwich]

Re: Vizio M70-C3 Dark Spots

:-) very wise on the "last thing to do" especially as a "first effort". Ultimately, I kind of doubt that to fix this set, there will be an easy / board solution.

[budm]

Re: Vizio M70-C3 Dark Spots

You have 32 LED strings, thus 32 power MOSFET's to control the current for each LED string. Using LED tester to look for open LED will be the easiest but you will have invest in the tool. Taking the LCD panel apart will be the last thing you want to do after all the testings are done.
https://www.shopjimmy.com/vizio-1p-1...led-driver.htm

https://www.shopjimmy.com/foxconn-s7...-16-strips.htm
Based on picture of the LED strip from SHOPJIMMY, it has 160 LED's total that I can see, so it means (if they are grouped equally) 5 LEDs per zone, you can use two 9V batteries connected in series to form 18V source than put 150 Ohms resistor in series to limit the current to about 30 mA for testing each set of LED.
5 LED's with current limit of 30 mA so total Vf of 5 LEDs = 2.70V x 5 = 13.50V.
18V - 13.50V = 4.50 V, 4.50V @30mA = 150 Ohms.
BTW, can you read the P/N of the LED driver IC U101, U102?

[nomoresonys]

Re: Vizio M70-C3 Dark Spots

Some say it's dirt n dust on the diffuser sheets.

[kentkirchner]

Re: Vizio M70-C3 Dark Spots

Please provide the pictures of the whole backside of the TV showing all the boards, then good clear straight shot of the whole board of each board.

Will post pictures this weekend...thank you

[kentkirchner]

Re: Vizio M70-C3 Dark Spots

Hello Diah, I restored the factory defaults and picture still the same. Next, I copied the black and white jpg's to a thumb drive and played them on a slide show for a couple minutes. I could always see the shadows when the white screen played.
Is that the tests you are asking for?
thank you,
Kent

[kentkirchner]

Re: Vizio M70-C3 Dark Spots

HI Guys, thank you very much for the great feedback, much appreciated! Appears I should focus on a couple areas, LED's and the local dimming aspect of the TV.
I think a good place to start is where BudM recommends, take off the back of the TV and snap some shots of the entire back, then of each board up close. I'll try and get a peek at the LED's as well without tearing the whole thing down. I have watched and studied several YouTube video, including ShopJimmy.com of replacing LED's on a 70 inch TV and not ready to jump there yet. :-)
I think I understand Diah's post, but not sure what I am looking for or the result of the test. I did the following:
I went into the System settings and restored the TV back to factory defaults, is this what is meant by a hard reset? In my world, a hard reset is unplugging and plugging back in, which I also performed.
Now, his next step, put on a thumb drive and play the white and black back and forth until the white screen is all white?? and if it nevers goes to completely white?
Oh, one other question, the Vizio site said this TV does have local dimming in 32 areas. So I looked on ShopJimmy.com and I see an LED driver board with 32 components. Does this board control the local dimming aspect of the TV? Seems logical. So if the LED's are all good, maybe need a new LED driver board..sorry for the long winded return, but ya'll had great thoughts.!!

[Diah]

Re: Vizio M70-C3 Dark Spots

The TV is working just fine, however, when a screen shot of white clouds came on the other day, I noticed several dark areas as shown in my attachment

on the specification of the this TV there are full arrow dimming system. as other said. this panel are big the risk to take out with one person do high.

reading voltage don't work at all as its currents to dimming or turn off. if there was one burned then whole back light will be out and TV will never start.
the rest we can think what i said before.. but its much we can know more close with easy steps

1- make hard reset from service menu and check result

2- attached UHD learning full arrow dimming system put them on fat32 usb format and play them on the tv one by one until you can see the white one full White.

if no change please report to do other test

[budwich]

Re: Vizio M70-C3 Dark Spots

since there seems to be a lot of areas... my guess is that you have been running the set "full bright" resulting in heating of the diffusers around the led resulting in some "burning" which has made them less transmissive. If the actual leds had problems, odds are high that the set would have shut down due to some form of voltage / current limits being set.

[mmartell]

Re: Vizio M70-C3 Dark Spots

If it has local dimming then the circuit controlling it may be faulty

[budm]

Re: Vizio M70-C3 Dark Spots

Please provide the pictures of the whole backside of the TV showing all the boards, then good clear straight shot of the whole board of each board.