Ideas on How to Dim a LED TV Backlight (Physically/ Electronic Components?)

tunzafun001 on 26/10/2021 - 18:48

I ve got a Chinese no name 3D TV that also does 4K. It has an LG panel, and the picture is quite good. It's lasted 5+ years, but the damn thing doesn't have a menu to turn down the backlight (it's rediculously bright).

If you enter the secret service menu via the remote (source,2,5,8,0) then there is a menu to turn down the backlight. Put it to 30% and it looks magnificent, power usage is 1/3rd.

However, as soon as you change channel, or source or just about any function it goes back to full bright. Light bleed everywhere. There is a 'save settings' that clearly doesn't work

So wondering if there is anyway to permanently set the backlight to 30%. For example, opening up and adding in a variable resistor or something like that to the LED backlight?

It's a great panel that produces an excellent picture, but is absolutely shocking in default settings.

Electrical & Electronics

Comments

  • jinny7 on 26/10/2021 - 19:07

    Completely no name?
    No make and model at all??

    Check with your place of purchase
    Ask for these details.
    Check with the manufacturer if you get them. Perhaps a firmware upgrade is available.

    I wouldn't recommend taking it apart.

    • tunzafun001 on 26/10/2021 - 21:11

      It's one of the generic OEM Chinese TVs. Teac and LG have the exact same hidden menu (which provides a firmware number etc, but I have searched everywhere). Maybe could use an LG firmware, but pretty sure it would brick it. The LG and Teac have a standard menu where you can adjust the backlight. This just has the standard OEM menu. So guessing they have an extra board, controller or something inside.

      My old man is a sparkie, so I have been pulling things apart my whole life. Reasonably comfortable. Just thought I'd see if anyone else has done this already.

      • jinny7 on 26/10/2021 - 22:57
        +1

        Fair enough.
        Personally I would prefer a less invasive method, with less risks.

        Number one: getting a fix from the manufacturer.

        If that's not available, option two would be:
        Get something that can playback infra red from the remote.
        Copy all the buttons and have a preprogrammed sequence played back to enter that service menu, reduce the brightness, and exit out back to the desired source input/channel.

        Many universal remote controls or hubs will do this, as a macro.
        So each time you flick to different input a single key could run the macro instead of you doing it manually.

        • tunzafun001 on 26/10/2021 - 23:31

          Interesting, never heard of this. Any links?

          I currently have it set up out the back connected only to a Bluray player/5.1 amp. Basically movies only. You can change settings on the Bluray player and the backlight will stay as selected.

          But as a normal TV where you change between channels and HDMI inputs etc, it defaults back to full bright every time.

          I guess with your method, every time you change a channel you would briefly see the service menu come up?
          As the backlight adjustment is service menu ->general settings -> BL -> 70. So you would see this menu flash up each time? Wonder how fast it could process it?

          I have an older Harmony remote (200) and made a copy of this remote in case it breaks. But don't think it can record / playback a sequence.

          Need to check my old phones/tablets/smartwatch to see if they have IR blasters. Maybe this?
          https://www.ebay.com.au/itm/154316941926?hash=item23ee01aa66…

          Even if i don't use it in the house. It would be a good 'upgrade ' so kids can use it without needing new retinas after an hour!

          • jinny7 on 27/10/2021 - 21:16

            @tunzafun001: Apparently the harmony 200 has one macro button available "watch tv":

            https://www.trustedreviews.com/reviews/logitech-harmony-200

            Logitech’s more expensive Harmony controllers are macro-heavy, offering plenty of buttons that will execute several commands from a single press. There’s just the one here – Watch TV. This will turn on the required devices and set your TV/home cinema amp to the right channel, ready to roll.

  • AndyC1 on 26/10/2021 - 19:08

    Google the importer in OZ and ask them.

    • tunzafun001 on 26/10/2021 - 21:15

      Ha, basically me. I bought it via Ali baba. I went into Harvey Norman at the time and they didn't even know what 4k was back then. The Chinese TVs were about 4 years ahead of what we have mainstream here. Actually not sure if a 4K 3D TV was even released here (not that there is any 4K 3D content). But at least it does both pretty well individually.

  • Typical16-bitEnjoyer on 26/10/2021 - 19:12
    +2

    Wear sunglasses.

    • Butt Scratcher on 26/10/2021 - 19:30

      /thread

      After 5 years of putting up with it, why have you decided that now is the time to try and address it?

      I'd probably try and lookup the model number before doing some serious research on it

      • tunzafun001 on 26/10/2021 - 22:01

        Got a two year old who is now pulling on the lounge TV. So wall mounted it. We watch mostly FTA in a small lounge, and I cant stand the pixelation on friends 60"+ TVs. So we still use a 42" Panasonic. However, once up on the wall, it looks like a postage stamp (and it is covering an old wall mount air con.. just).
        So this TV is 50", but looks horrible at full brightness (plus uses 3x the power of the Panasonic). However, when the backlight is dimmed in the service menu it looks great and uses exactly the same as the Pana. It's been sitting in the shed. Time to tweak it or turf it.

      • tunzafun001 on 02/11/2021 - 12:05

        The hidden menu says the board is a BD_MSD309_29x

        Amazingly, if you google it, you get zero hits..nada, nothing.

        Seems the MSD309 is a base board many manufacturers build upon. At least that's what I think is happening.

  • aussieprepper on 26/10/2021 - 19:31

    Yea add a resistor to the backlight to limit the amount of current flowing through to the LED's. If you wanted it twice as dim use a resistor that is double in value from the original if you can get the original resistor of the board.

    • tunzafun001 on 26/10/2021 - 21:52

      That's what I was thinking, but is it as simple as a resistor in a tv? Got nothing to lose I guess.

      • aussieprepper on 26/10/2021 - 22:36
        +1

        It will be controlled now by a some sort of driver board that is using PWM to dim/control the LED array, the driver should have your usual components like a control chip, mosfet and resistors and maybe some caps to smooth out the signal, maybe a coil. If you can find the sense resistor that controls the hard current limit to the LEDs you will be able to the lower the max current, this will lower the brightness.
        Other option is to reprogram the chip that is controlling the LED's.

        All boards will be different but this boards looks pretty basic.
        https://ae01.alicdn.com/kf/HTB1d.Nba7WE3KVjSZSyq6xocXXa3/LED…

        • tunzafun001 on 26/10/2021 - 23:14

          Thanks mate. Very helpful. Will give it a crack. Cheers..

        • tunzafun001 on 31/10/2021 - 16:05

          Just went for a stroll to get some surface mount components (hard rubbish day). Eko branded TVs everywhere!!
          Will gut one and have a look at the backlight management circuitry before playing with mine.

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