701c brightness button problem

[schnitzelcore]

When I press Fn + brightness up/down on my 701c the 'sun' icon appears and the bar moves up or down, but there is no perceivable change in brightness.
I read in the hmm for another old model this can indicate a hardware malfunction. The screen is functioning normally in all other respects.

[schnitzelcore]

*BUMP*

Can anyone give me an idea what kind of odds I would have of fixing this problem by reseating the LCD connector as the HMM suggests? And would not fixing it only mean I'll get a bigger failure within the foreseeable future or could this situation stay stable? (I don't really have a problem with the brightness of the screen per se, it's just I don't like the fact the machine is not operating as it should.)
I do not have the tools to open a 701 (would have to buy those first) and there's always the chance something goes wrong when working on an old machine like this.

[RealBlackStuff]

I just repaired a 701c for a forum member here.
To open it up, you need a Torx T1 and a Torx T6 screwdriver.
I think "Aurora" in the Vijzelstraat (near de Munt) in Amsterdam might have those.
Once open, reseating the LCD cables (2 adjacent small ones) is "een fluitje van een cent".
While open, check for corrosion on the battery contacts and around the CMOS battery connector.
That was the problem with the one I just fixed, although this one wouldn't boot up at all when I got it. Dead as a dodo.