Is my TV cooked?

L

Lazzy

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Hi All...

Our 4 yr old Lg 42 inch led tv picture is getting dimmer, can still see-watch it but somethings obviously on its way out so wondered if we have any experts on here who can hopefully guide me in the right direction.

Is it likely the led backlights are failing or is it likely the power supply board is causing the lights to dim or fail. Anyone know what the voltage should be at the led pin connecter ? There's only 2 wires. It's an Lg42LF561v, Thanks.
 
There are lots of videos on Youtube dealing with LG backlight issues. Here's one such video that talks about the dim screen issue. Skip forward to 0:54 to see the specific issue.



Use it as a starting point for further investigations about the cause.
 
Thanks for taking the time Lucid, I have been looking at those tutorials on yt but couldn't find one on picture dimming and what to check and look out for. I've been given the ultimatum fix it by monday or get frog marched to Argross on tuesday. sigh.
 
Backlight issues are not unique to LG. Other brands suffer the same fate too. It's something to bear in mind if purchasing between entry-level and midrange in the Korean brands and anything from other brands besides Sony and Panasonic. However, LG has earned itself a particularly poor reputation because of higher-than-average backlight failures in its entry- budget- and mid-level ranges.

The issue has come about partly because of the constant drive for lower prices, which is a situation created by the Korean brands' race to beat the Japanese and European makes; and from the push to make HDR accessible on cheaper TVs.

All of the manufacturers are trying to stretch what they do for a specific budget. LG though has made a habit of trying to "out feature" it's competitors at a similar price point: If a Samsung has Freeview then an LG will have Freesat and Freeview. If the Samsung has two USB ports then the LG has three. etc etc. What LG has been crafty about though is dropping lesser-used features, e.g. the headphone socket, or just not supporting some stuff such as Freeview Play and iPlayer in some of its TVs. It's robbing Peter to pay Paul.

One area where they've come unstuck - in both a figurative and a literal sense - is with backlights.

The problem here is simple. For a 4K TV with HDR, the backlighting needs to go appreciably brighter with HDR content than with ordinary non-HDR images. There's no short-cut; the TV needs either a few very bright LEDs, or a lot of LEDs. Bright LEDs cause their own problems though because it's harder to diffuse the high intensity light over the short distance behind the LED matrix which means the lighting looks uneven. The better option is a lot of LEDs. This is where LG has decided to economise though.

What they've done to reduce costs is cut the numbers of LEDs and then to drive the remaining ones harder. The result is that the backlight is running near maximum just for ordinary TV viewing, so there's not much left in reserve for the extra boost needed for HDR. At the same time, the LG screens aren't particularly bright for their price level anyway. The result is for someone viewing in high ambient light they'll have to drive the screen brightness harder to get a watchable image but won't realise they're pushing the LEDs flat out as a result. This is why they're failing prematurely.

Fixing the backlight isn't like changing a light bulb, but it's not brain surgery either, and so anyone with a bit of technical sympathy can probably do it once they've seen the process in a demo video. Depending on the size of the TV the job can be completed for a parts cost of between £40 and £100 typically. What you'll struggle to do is to get that done next day. You might need to negotiate a time extension in order not to waste money on another TV with weak backlights.
 
If it's within the budget, then the LG OLEDs are worth it IMO. The 55" OLED55BX6 isn't perfect if you're an avid gamer or have a room with a lot of ambient light, but compared to most 55" TVs around the £1,000 mark it's probably one of the most impressive.

I'm less enamoured of the LG Nanocell sets; even the higher-end ones close to OLED prices. They're just not good value when you start to dig in to the specs.

For example, the 55NANO806PA sells for around £950 so it's definitely not what I'd call mid-range LED-LCD. It's well above that, IMO. However, it still has just a 50Hz 8bit panel and is edge-lit. Sure, it has wide viewing angles, Freesat HD and the magic remote with it's mouseball pointer (it's BT, not magic), but the fundamental features that make a difference when watching both ordinary TV and 4K content are very-much lacking.

Compare and contrast the £950 LG with the £1000 Sony 55" XH9505. Here you get a 100/120Hz true full-10bit panel with full array local dimming. You also get Dolby Vision which is missing from the LG. By all accounts the Sony goes much brighter too because they fit decent backlights. There's a useful review of the Sony at rtings. They've also done a review of the LG Nanocell set. Just compare the screen brightness readings:

for ordinary TV viewing, DVDs, Blu-rays, non-4K content etc:-

LG's SDR Real Scene Peak Brightness 207 cd/m² - this is about what I'd expect from a £450 Sharp / Hitachi / HiSense / Samsung / LG. No one should be paying nearly £1000 for a TV and getting this kind of brightness output.

Sony's SDR Real Scene Peak Brightness 565 cd/m²

The Sony is almost 3x brighter than the LG in real world usage​


for UHD 4K HDR streaming/download, Sky/Virgin UHD, and UHD BD discs:-

LG's UHD HDR Real Scene Highlight 247 cd/m² - a 19% increase in brightness compare to SDR

Sony's UHD HDR Real Scene Highlight 980 cd/m² - a 73% increase in brightness compare to SDR​

The Sony is almost 4x brighter for 4K UHD HDR​
 
Check your backlight setting on your panel tv, try to keep it around 70% or less if you can - it will prolong the life of your LEDs and your tv. You might get an extra week out of it if you're lucky. /s
 
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