Replacing 755CSE Screen with 755CX? Only 1 slider?

[clamic235]

I've been putting this off since 2019, but after a surge of motivation I looked into a replacement screen for my 755CSE again. I saw that screen assemblies for the 755CE, 755CSE, 755CX, and 755CV are all compatible apparently. The 755CSE has two sliders though, one for contrast and one for brightness. Other models, such as the 755CX only has one slider.
With a slider missing on the new screen assembly, how would one control the other function that would now be absent? Is there any way to replace just the LCD part so I can maintain control of both brightness and contrast? Or if I want to do that will I have to specifically find the exact same replacement assembly? Thanks for any guidance! If someone could provide pictures of the inside of a 755CX screen assembly that would be appreciated too.

Going based off what I'm seeing here: https://thinkpads.com/support/hmm/hmm_pdf/tpvol2.pdf on page 453.

[solidpro]

My experience is that when you see a reference to LCDs being 'compatible' it basically means the entire LIDS are compatible from different models.

Put another way, if you want to change the LCD, you also need to change the cables from the LCD to the motherboard and in some cases you also need to change the lid that it bolts too and in rare cases the hinges and some other bits of plastic.

I've also noticed the slider differences. In some cases this is the different between a DSTN which often contains brightness and contrast and TFT which usually only has a brightness display (as the better field of vision makes the contrast control pointless).

You can find the inside of the all of the 755 assemblies in the HMM here: https://thinkpads.com/support/hmm/hmm_pdf/tpvol2.pdf

[Psyberducky]

Funnily enough, on my SVGA TFT 755CX, there are actually two sliders on the screen, but the contrast slider is covered by plastic when the bezel is installed! This was a surprise when I took it apart.
The contrast slider was fixed in the exact middle with a plastic wedge, but if I removed that, it worked normally in both directions.

[solidpro]

Wow that's a weird find. Never noticed that, but I am about to go to work on a 755 so will find out soon!

I always thought there wasn't any point in brightness and contrast anyway - contrast seemed to always just do 'a bit' of brightness....

[clamic235]

I've also noticed the slider differences. In some cases this is the different between a DSTN which often contains brightness and contrast and TFT which usually only has a brightness display (as the better field of vision makes the contrast control pointless).

So since I'd be going from a DSTN screen to TFT, the contrast slider will no longer be needed anyway? So I can just take the entire screen assembly off the 755CSE, install the one from the 755CX, and it would work as expected? Just want to clarify before I go out and buy anything. Thanks!!

[solidpro]

That might well be what you have to do because in my experience the cable going from the motherboard to the LCD and the inverter will be completely different between DTSN and TFT.

If you can just take a whole working TFT lid off another machine then do that.

[clamic235]

That might well be what you have to do because in my experience the cable going from the motherboard to the LCD and the inverter will be completely different between DTSN and TFT.

If you can just take a whole working TFT lid off another machine then do that.

Thank you!

[clamic235]

I ordered the 755CX screen and installed it, works perfectly. Thanks all who replied! Happy to have finally done something about it lol
Before and after:

[solidpro]

Looks brilliant! Did you replace just the LCD or the whole lid in the end?

[clamic235]

Looks brilliant! Did you replace just the LCD or the whole lid in the end?

The whole lid, so LCD, bezel, and all. I had wanted to replace just the LCD since the rest of the lid assembly was in great condition, but a working screen in a more scuffed lid is better than a broken screen in a pristine lid lol. And finding a replacement lid from any compatible model is much more practical than finding just the LCD, or buying a lid for this specific model just to take the LCD out. Thanks for your assistance ITT!

[goldeneagle]

Looks brilliant! Did you replace just the LCD or the whole lid in the end?

The whole lid, so LCD, bezel, and all. I had wanted to replace just the LCD since the rest of the lid assembly was in great condition, but a working screen in a more scuffed lid is better than a broken screen in a pristine lid lol. And finding a replacement lid from any compatible model is much more practical than finding just the LCD, or buying a lid for this specific model just to take the LCD out. Thanks for your assistance ITT!

Nice work! I did the same on some of my machines. The 800x600 LCD always beats the 640x480.

[clamic235]

The whole lid, so LCD, bezel, and all. I had wanted to replace just the LCD since the rest of the lid assembly was in great condition, but a working screen in a more scuffed lid is better than a broken screen in a pristine lid lol. And finding a replacement lid from any compatible model is much more practical than finding just the LCD, or buying a lid for this specific model just to take the LCD out. Thanks for your assistance ITT!

Nice work! I did the same on some of my machines. The 800x600 LCD always beats the 640x480.

Thanks! The higher res screen is very nice I hope it doesn't succumb to vinegar syndrome as well. Should be okay for a long time at least because I keep it in the basement which stays cool and dry. Before I owned it it was in a garage in coastal Florida I believe; definitely get why the poor DSTN screen looked the way it did.

[goldeneagle]

Vinegar syndrome is weird... it seems to affect some screens and not others, even when they were stored in the same place and conditions (which I've witnessed firsthand).

Worst case scenario, which might be a crapshoot at best, is replacing the polarizers, which gets rid of the vinegar syndrome problem. And then you run into the next problem - the polymer capacitors taking a crap, resulting in a poor or non-existent image. Hard to believe these machines are now at or nearing 30 years old!