PCE GT / Turbo Express: uneven brightness (stock screen), fix ?

[TheShadowRunner]

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]

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]

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 :/

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]

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]

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.

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]

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]

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]

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]

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 ?

[TheShadowRunner]

No interest anyone? This ^ might be why stock screens have uneven brightness.
If I wasn't so scared I'd try to adjust / re-center the backlight bulb on my unit but opening the LCD makes me way too uneasy.

So if a skilled individual (pretty much you Keith ) could look into it a little deeper, I believe you have a number of spares
Or has everyone forsaken the stock module yet...

[MasterofBiscuits]

Honestly never seen this myself, and I have seen a lot of stock screens. My guess is maybe a faulty lamp. Pretty sure it's not due to the positioning of the CCFL because all the screens I've seen have even brightness.

I have had a play around with LED backlights but I haven't yet been able to find one that is strong enough without getting too hot. Since the screen is a sealed unit I'm worried about heat causing problems with the LCD. Also not sure there is much value in it, given that RGB screen mods are so easily done nowadays.

[TheShadowRunner]

Honestly never seen this myself, and I have seen a lot of stock screens. My guess is maybe a faulty lamp. Pretty sure it's not due to the positioning of the CCFL because all the screens I've seen have even brightness.

Hmm you must be super lucky for I remember that flaw since the 90s and it's affecting my current unit as well.
Keith has also inspected at least 4 spare stock units with the same flaw.
To be clear, and it may likely be inherent to the technology :
Brightness isn't uniform across the screen. I have taken 2 videos to emphasize the issue:

-

The gray bar at the bottom is supposed to be unifom across the screen, but as you can see when modifying the brightness it's not uniform at all, the bottom left part where it says NEC AVENUE is always brighter.

-

Best test: after selecting the middle "Dual Scramble!" option, the left and right options "Blaster1 / Blaster2 Scramble" are supposed to be identical faint gray. When lowering the brightness to an acceptable level for the left one, the right one totally disappears !

So if you have a spare unit that doesn't exhibit the issue, I'm interested!

[Keith Courage]

There is no way to recenter the bulb. The bulb would need to be changed to fix but I haven't been able to find a suitable replacement.

[MasterofBiscuits]

Hmm you must be super lucky for I remember that flaw since the 90s and it's affecting my current unit as well.
Keith has also inspected at least 4 spare stock units with the same flaw.
To be clear, and it may likely be inherent to the technology :
Brightness isn't uniform across the screen.

Ok I understand now, you are talking about a design flaw and not a fault? I thought you were talking about a particular screen.

You could try masking off the longer side of the bulb, or put another diffuser over it to make the light more even.

The bulb is only held in with pressure and some sticky tape along the bottom so you could in theory bend the contacts, but you would probably also need to cut away some plastic on the back piece of the screen case.

Or....just put a 3.5" screen in there like everyone else

[Necromancer]

I pulled mine out for a peek, and I can't see much difference in brightness across the screen.  I ain't getting any younger, though, so maybe I'm just blind.   

If I were at all concerned, I'd do a screen replacement.  The OG screen was good for the time, but it's complete shit compared to anything remotely modern.  Reading the TED menus (and even playing Hatris) was tough.