Author Topic: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?  (Read 130 times)

TheShadowRunner

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PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« on: February 03, 2021, 01:15:27 PM »
Hi all,
The brightness on my stock GT LCD is uneven : the left part of the screen is brighter than the right, and when I raise brightness with the knob, left side brightness increases before the right.
I'm unable to get brightness uniformly accross the screen, it's annoying ^^;

All caps were replaced professionally by mobiusstriptech, ultrasonic cleaned, and the LCD is otherwise flawless (no dead pixels).

I don't think the LCD module is damaged per say and the flaw could be inherent to the old technology but,

1. Do you experience this on your system ?

2. Is there a way to improve or fix this ?

3. In case it's not user fixable, are there trustworthy sellers that sell tested stock LCD modules on this forum ?

Thanks for any tip / advice!

Keith Courage

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Re: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« Reply #1 on: February 04, 2021, 02:56:08 AM »
It's the light inside the screen. The right side is generally brighter than the left. Some worse than others. Usually after warming up this becomes less apparent.

If not then the only option is to replace the light bulb inside the screen or replace the screen itself. Although lots of other stock screens do this as well.

TheShadowRunner

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Re: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« Reply #2 on: February 04, 2021, 02:26:03 PM »
It's the light inside the screen. The right side is generally brighter than the left. Some worse than others. Usually after warming up this becomes less apparent.
Thanks, do you mean the mini-neon used as backlight is itself uneven ?
The left side is brighter here, and warm-up has no impact :/

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If not then the only option is to replace the light bulb inside the screen or replace the screen itself. Although lots of other stock screens do this as well.
Would you have a part number or details on the bulb ?
Ideally I'd love te upgrade the LCD module with recent technology, but there seem to be no direct drop-in / non-destructive 2.6" screen replacement solutions (I'd want to keep it as original as possible, RGB, av-in of TV Tuner working..).
Do you have some of those old OEM modules for sale yourself ? I see you are a PCE repair guru ^^

Keith Courage

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Re: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« Reply #3 on: February 04, 2021, 09:46:20 PM »
Yes, it's bulb inside the screen. Sorry I have no source for a replacement.

I do have a number of old stock screens on hand since I regularly do the 3.5" lcd screen upgrades.

The next time I do some repair on an express, I will go through some of the screens I have and find a good one for you. Probably within the next few days.

TheShadowRunner

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Re: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« Reply #4 on: February 04, 2021, 10:28:31 PM »
Yes, it's bulb inside the screen. Sorry I have no source for a replacement.
Man if it was somehow possible to replace the bulb backlight with a led-based solution it'd be ideal, oh well.
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I do have a number of old stock screens on hand since I regularly do the 3.5" lcd screen upgrades.
The next time I do some repair on an express, I will go through some of the screens I have and find a good one for you. Probably within the next few days.
That'd be nice! The 240p suite HuCard rom should be handy for testing ^^;

MasterofBiscuits

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Re: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« Reply #5 on: February 06, 2021, 07:04:41 AM »
Man if it was somehow possible to replace the bulb backlight with a led-based solution it'd be ideal, oh well.

Yes you can do this it is not difficult. You simply remove the CCFL and desolder the holder and replace with some LEDS such as this: https://www.aliexpress.com/item/4000805192753.html These only draw 200ma, so it would be fairly power-efficient and they do not run hot.

Just run a wire to the large pad of the voltage regulator on the mainboard for the 5v, and another wire for ground.

I got part way through designing this mod but then found I could just use a 3.5" screen so I didn't finish it, but I did go as far as getting it running. All I would say is use some warm LEDs, as regular white ones give a blue tint to the picture. I was also able to revert the whole thing back to stock easily.

TheShadowRunner

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Re: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« Reply #6 on: February 06, 2021, 12:46:13 PM »
Yes you can do this it is not difficult. You simply remove the CCFL and desolder the holder and replace with some LEDS such as this: https://www.aliexpress.com/item/4000805192753.html These only draw 200ma, so it would be fairly power-efficient and they do not run hot.
Just run a wire to the large pad of the voltage regulator on the mainboard for the 5v, and another wire for ground.
I got part way through designing this mod but then found I could just use a 3.5" screen so I didn't finish it, but I did go as far as getting it running. All I would say is use some warm LEDs, as regular white ones give a blue tint to the picture. I was also able to revert the whole thing back to stock easily.
That's very interesting, thank you !

Doing it this way, would the brightness knob still work ? What about the auto power-save timeout?

While I'd try if I had a spare module, currently my goal is still to have a proper working stock LCD ^^

MasterofBiscuits

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Re: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« Reply #7 on: February 07, 2021, 04:59:23 PM »
Brightness knob will still work, I'm not sure about the screen timeout but I think it should.

One day when I have time I will do the mod and document it here. I think it could be quite useful for some.

TheShadowRunner

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Re: PCE GT / Turbo Express: uneven brightness (stock screen), fix ?
« Reply #8 on: February 21, 2021, 09:18:44 PM »
Here are hi-res pics of the LCD module disassembled:

https://upload.wikimedia.org/wikipedia/commons/a/a8/NEC-TurboExpress-LCD-Dissembled-1.jpg

https://upload.wikimedia.org/wikipedia/commons/7/70/NEC-TurboExpress-LCD-Dissembled-2.jpg

If you check carefully the bulb isn't centered in an optimal fashion, its right end (dimmer) is way closer to the edge of the screen than left end (brighter), could it be the source of the flaw.. Interesting!


@MasterofBiscuits, did you notice uneven brightness on your stock LCD as well ?