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Old 01-14-2018, 10:02 PM   #1
maxvalutech
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Default VIANO LED40FHD backlight on/off

Got this set and owner advised good sound but no picture. Turned it on and no sign of backlights. Opened it up to take voltages - only 2 wires for backlights and at standby 26v showing, switched on and this time backlights flashed on/off then read 37v, turned it on and off a few times and once backlights stayed on for about 7 seconds with voltage rising to just over 90 before they again went off. They are intermittent at start up. Main cap good at 364v. This set is a Chinese generic with a market name. Someone may recognise the all in one board but in any case what components would you be checking?.
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Old 01-15-2018, 06:36 AM   #2
Andrew F. Ali
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Default Re: VIANO LED40FHD backlight on/off

The backlights is your problem. You would have to strip down the panel to reach them. Probably one or two LEDs on the strips bad. i.e. opened or shorted. LED Driver good as you saw 90Vdc the one time when the backlights stayed ON. This is an easy fix.
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Old 01-23-2018, 02:25 PM   #3
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Default Re: VIANO LED40FHD backlight on/off

Andrew F. Ali your right though I'm not too sure re the easy bit ! Took me about 30mins dismantling to find the backlights ! As I worked it was obvious by missing screws etc that someone had gone before me and sure enough 4 replacement LEDs seen on one strip. The strips are UL-E469119 and well advertised except here in Oz. I have to test them now but no power supply as such so just wondering if I can use a small 9v battery on each of the strips to find the ones going blown or shorted ??
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Old 01-23-2018, 04:22 PM   #4
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Default Re: VIANO LED40FHD backlight on/off

I have connected set to power and have red standby that turns green when on/off button activated but not a flicker from backlight LEDs which are still connected as the all in one board is on rear of backlight panel. Don't know if screen non connection is a factor but don't see why it should be. Also, with dmm in diode mode and a strip disconnected from the others again no sign of life from LEDs when probes on plus and minus at end of that strip.
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Old 01-23-2018, 04:34 PM   #5
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Default Re: VIANO LED40FHD backlight on/off

Pic with backlight paper removed.
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Old 01-23-2018, 04:50 PM   #6
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Default Re: VIANO LED40FHD backlight on/off

Quote:
Originally Posted by maxvalutech View Post
I have connected set to power and have red standby that turns green when on/off button activated but not a flicker from backlight LEDs which are still connected as the all in one board is on rear of backlight panel. Don't know if screen non connection is a factor but don't see why it should be. Also, with dmm in diode mode and a strip disconnected from the others again no sign of life from LEDs when probes on plus and minus at end of that strip.
You can't check a whole row of LEDs using this method. Diode mode is about 0.5v and those LEDs are 3v. You should see a faint glow testing individually though.
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Old 01-23-2018, 06:25 PM   #7
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Default Re: VIANO LED40FHD backlight on/off

Thanks diif I had seen they were 3v but didn't know dmm output. At 1.5v per led went ahead with 9v battery and isolated strips lit up individually except for the lhs centre strip in pic above - but funny that that strip has no black (neg) lead going to it just red and red out ?? Anyway that strip didn't light so will now do individual LEDs test on it. Oh yes battery test was neg to pos to get lights up.
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Old 01-24-2018, 04:16 PM   #8
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Default Re: VIANO LED40FHD backlight on/off

I certainly don't know much about LEDs except they seem hard to find for replacement as most ads are for coloured ones!! Tried testing individual but no glow for me - used track scratches made by previous tech. Anyway a close visual inspection shows first led in strip blown also the last one in the strip is also showing a bit of brown burn. Anyone have a reccomend for replacement purchase - don't mind a wait but won't pay high postage costs .
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Old 01-24-2018, 04:19 PM   #9
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Default Re: VIANO LED40FHD backlight on/off

Pics showing detail
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Old 01-25-2018, 11:19 PM   #10
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Default Re: VIANO LED40FHD backlight on/off

Set up a 1.5v battery and tested individual LEDs to find 4 not working on the strip. All the LEDs in the set are on one single input. Have ordered strip of 6 LEDs via yoycart.com and will just have to see if I can adapt them to work - same voltage ul-e469119 but no dimensions given and other numbers differ. Postage high but airmail so will see how it goes. Don't like having set/screen apart for too long.
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Old 02-13-2018, 03:53 PM   #11
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Default Re: VIANO LED40FHD backlight on/off

Received my led strip order and had to get 12 strips x 6 LEDs so have plenty on hand if any in Oz want some. As suspected these strips longer than the ones in set which it turns out are wired differently than I expected. I assumed straight series wiring but circuit when traced on the board shows 2 lots of 3 LEDs wired together on each strip. So did a diode check and only the ones each end are bad. The bought ones are straight wired from connector to other end of strip and then to each led in turn back to connector. So I now have choices 1. Do I take two LEDs from purchased ones and put these on strip from set or 2. Do I cut the long strip down to 4 LEDs bridge the + to - with a solder dab after the last last led on lhs and cut backing paper to suit? Also connectors are not the same so would need to either swap them over or solder wires direct to strip. I don't see voltage problems with two less LEDs as difference of 36 to 34 into 94v is minor and LEDs are 3v. Which way would you go??
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Old 02-13-2018, 08:18 PM   #12
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Default Re: VIANO LED40FHD backlight on/off

Well in the end I decided to use new strip and 5 LEDs. A bit of soldering and this is the result which I hope will look OK. Now for getting the screen back together !! Who said an "easy repair" :-)
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Old 02-13-2018, 10:13 PM   #13
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Default Re: VIANO LED40FHD backlight on/off

Carefully put screen pieces back in under the 4 trim strips then turned the assembly over to fit into outer panel and surround which I had laid down on cushioned flat surface. All seemed to go OK so screwed top and sides down then connected bottom ribbon and checked PCB sitting OK. Decided to check this before proceeding further so fired set up to get a nice glow from backlighting and a "no signal" on screen when I gently lifted frame to have a look, then pressed menu and that came up too but suddenly all went off as screen cracked!! Double damn!! Not sure why it went but I think either I put wrong size screws in the outer trim or the panel stressed too much as bottom screws affixing it were not fitted at that stage. In any case a good learning curve.

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Old 02-14-2018, 08:21 AM   #14
Andrew F. Ali
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Default Re: VIANO LED40FHD backlight on/off

Quote:
Originally Posted by maxvalutech View Post
Well in the end I decided to use new strip and 5 LEDs. A bit of soldering and this is the result which I hope will look OK. Now for getting the screen back together !! Who said an "easy repair" :-)
Good work, my Friend. You did well and made some excellent decisions while doing it. You see??.....Next time you have another one to do it would be easier and the more you do the easier it would become.......So easy repair.
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Old 02-14-2018, 09:16 AM   #15
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Default Re: VIANO LED40FHD backlight on/off

Quote:
Originally Posted by maxvalutech View Post
Received my led strip order and had to get 12 strips x 6 LEDs so have plenty on hand if any in Oz want some. As suspected these strips longer than the ones in set which it turns out are wired differently than I expected. I assumed straight series wiring but circuit when traced on the board shows 2 lots of 3 LEDs wired together on each strip. So did a diode check and only the ones each end are bad. The bought ones are straight wired from connector to other end of strip and then to each led in turn back to connector. So I now have choices 1. Do I take two LEDs from purchased ones and put these on strip from set or 2. Do I cut the long strip down to 4 LEDs bridge the + to - with a solder dab after the last last led on lhs and cut backing paper to suit? Also connectors are not the same so would need to either swap them over or solder wires direct to strip. I don't see voltage problems with two less LEDs as difference of 36 to 34 into 94v is minor and LEDs are 3v. Which way would you go??
This method is also good for repairing leds
https://www.youtube.com/watch?v=RxwdC7V5Ue0
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Old 02-14-2018, 07:31 PM   #16
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Default Re: VIANO LED40FHD backlight on/off

Quote:
Originally Posted by vinceroger69 View Post
This method is also good for repairing leds
https://www.youtube.com/watch?v=RxwdC7V5Ue0
Yes that's a good tip as I think the individual LEDs themselves are so small and my hands not very steady these days.. Would also work to cut the bad one out of strip and replace another good one in with appropriate soldering of connections. I went with new strip in this case as existing strip showed some colouring around LEDs being evidence of hard work I guessed.
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Old 03-12-2018, 12:06 AM   #17
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Default Re: VIANO LED40FHD backlight on/off

Maxvalutech, Do you still have any of those Leds for sale as I have exactly the same Viano tv in for repair and two leds are faulty on one of the boards. The rest are all ok.
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Old 03-12-2018, 01:59 AM   #18
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Default Re: VIANO LED40FHD backlight on/off

Hi. Do you want just a couple or a strip. Happy to send to you for postage cost.
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Old 03-12-2018, 04:50 PM   #19
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Default Re: VIANO LED40FHD backlight on/off

A strip would be awesome thanks mate. Tell me how much and where to deposit the money too?
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Old 03-12-2018, 05:11 PM   #20
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Default Re: VIANO LED40FHD backlight on/off

Have you still got your old one as If I could just get an original strip , no soldering would be required , just plug and play lol.
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