The screen of the COMPAQ C140 doesnt turn On

I recently acquired a COMPAQ C140, its in a perfect physical condition, i put new batteries on it, but the screen doesnt turn on.

The only thing that happens when i adjust the brightness, is that the screen turns GREEN, but thats all.

I have already tried resetting the Compaq, taking out the Back Up batttery, but nothing happnes.

That being said, the Compaq does work, because when i write on the keyboard, the machine makes the sound, just as when you write on your phone.

So, please, how could i fix it? Has anybody had a similar experience?

It doesn’t really answer your question but this Reddit thread is worth a read of all of the troubleshooting they tried

https://www.reddit.com/r/retrocomputing/comments/1459lga/need_help_i_bought_double_a_batteries_for_a/

Also can you try adjusting the contrast to the minimum and maximum settings and seeing if that makes it any more readable ?

I mean, if that post you linked to isn't by the OP it's either a really common problem or he bought that exact device.

...the most recent "Sold" one on eBay states it has this exact problem so I'm guessing it's the latter.

It could be that the device thinks that the display is closed due to the switch that detects this being stuck. I had this problem on my Jornada 680 once, the screen would light up but no contents were displayed and I could still hear keyboard clicks and other OS sounds indicating that the machine was operational. Opening and closing the display a couple of times fixed the issue for me.

I'm not sure if the Compaq C140 has such a switch, if I had to make a guess, it could be located inside the small hole where the latch falls into to keep the display closed, might be worth fiddling with the mechanism for a bit to see if that solves the problem.