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Crumbtrail TV Forums: TV Equipment: TV Repair Forum:
Flashlight test reveals picture and no back lights are visible.

 
 


Danimal1q2w3
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Nov 20, 2015, 10:06 AM

Post #1 of 8 (1245 views)
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Flashlight test reveals picture and no back lights are visible. Can't Post
The TV in question is a Vizio M550vse. I have replaced the LED Driver board. When the TV turns on it flashes the Vizio logo, including back light for a brief second, then nothing can be seen until all the lights are turned off and a flashlight is applied to the screen. So the screen is working, but still there is no backlight, even after replacing the LED driver board. There was absolutely no change by installing the new part. How do I fix this?? TV is barely over a year old. As a PC repairman my instinct is telling me that it could be a problem with the power supply or the LED's themselves, but don't want to waste (more) money on parts that won't fix the problem. Thank you



jts1957
Veteran


Nov 20, 2015, 11:38 AM

Post #2 of 8 (1240 views)
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Re: [Danimal1q2w3] Flashlight test reveals picture and no back lights are visible. [In reply to] Can't Post
I'd arrange to observe the LEDs directly to see if one or more fail to light.


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Location: Far, Far Away


Danimal1q2w3
New User

Nov 20, 2015, 11:41 AM

Post #3 of 8 (1236 views)
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Re: [jts1957] Flashlight test reveals picture and no back lights are visible. [In reply to] Can't Post
The only time the LED's light up is when i turn it on and last for about a half of a second. Otherwise they are completely off.


jts1957
Veteran


Nov 20, 2015, 12:39 PM

Post #4 of 8 (1235 views)
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Re: [Danimal1q2w3] Flashlight test reveals picture and no back lights are visible. [In reply to] Can't Post
I'd have to CAREFULLY take apart the panel to see them each light or not ...

http://www.cnet.com/...acklights-explained/


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Location: Far, Far Away

(This post was edited by jts1957 on Nov 20, 2015, 12:42 PM)


Danimal1q2w3
New User

Nov 20, 2015, 1:03 PM

Post #5 of 8 (1231 views)
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Re: [jts1957] Flashlight test reveals picture and no back lights are visible. [In reply to] Can't Post
But none of the LED's are on


jts1957
Veteran


Nov 20, 2015, 2:54 PM

Post #6 of 8 (1229 views)
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Re: [Danimal1q2w3] Flashlight test reveals picture and no back lights are visible. [In reply to] Can't Post
Quote
When the TV turns on it flashes the Vizio logo, including back light for a brief second
With ALL the LED bulbs visible, do ANY fail to light during the above time frame? Of course with the LEDs removed from the proximity of the TFT matrix you will NOT be able to discern any video on it (unless you shine your own light source from behind it while it's apart - works even better than when a flashlight is shone from the front).

If you go into menu settings and select LED backlight, I think you'll find that the LEDs are being pushed at 100% Duty cycle and 100% Intensity.


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Location: Far, Far Away

(This post was edited by jts1957 on Nov 20, 2015, 3:00 PM)


Danimal1q2w3
New User

Nov 20, 2015, 4:02 PM

Post #7 of 8 (1225 views)
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Re: [jts1957] Flashlight test reveals picture and no back lights are visible. [In reply to] Can't Post
Why do you think the backlight was set to 100%


jts1957
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Nov 20, 2015, 4:51 PM

Post #8 of 8 (1223 views)
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Re: [Danimal1q2w3] Flashlight test reveals picture and no back lights are visible. [In reply to] Can't Post
The TV manufacturers will tell you that at those settings you will get the brightest, most vivid pictures. Most default to 100% as their butts are covered by those features being capable of customer adjustment downwards. Imagine TVs shipping with Volume at 100%.
They don't inform you that the set uses the most power, producing the most heat and negatively affecting the lifespan of the TV parts, especially the LEDs. Of course, if the sets lifespan is shortened the manufactures will make more money sooner as you replace the set.


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Location: Far, Far Away

 
 
 


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