180c contrast drifting issue - inverter board caps?

[3lectr1cPPC]

Great to see yours is working better now! Since then, I've used it a bit and gotten some software installed and it's mostly been ok. I've had a couple flickers here and there, so I'll probably try to do the proper fix and resolder the pot soon. It's definitely the issue though!

 

[MacUp72]

Not to call victory too early but I think I found the problem…

So, I was going about trying what @techknight suggested about poking at the board while it’s running. So, I took the front display bezel off and turned it on to find that as soon as the display finished initializing (the initial white screen went away, aka the computer took over control), it instantly went dark gray. I decided to mess with the voltage pots. Upon adjusting the pot labeled “V7”, it went away. I found that shorting any part of the pot to ground caused the display to go all gray again. The legs on it are a bit corroded so it’s probably a bad connection. For now, I’ve had it on for several minutes and the display looks perfect. If the issue comes back I’ll try to remove, clean under, and resolder the V7 pot, but it’s good for now!

Why don’t you give that a go @mattia1071 and see if it fixes your issue!
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Edit: I've had it on for around 20 minutes now and there's no sign of the issue! I think this one may be fixed!

wow, that display looks good now..I wonder what pb models have those pots

 

[3lectr1cPPC]

Perfect timing with the bump actually because I was just working on this one again a couple nights ago. My issues never went away, the laptop would start with the contrast dark like in the photo, then fade or jump to normal after being on for a few minutes, with an occasional flicker here and there. The colors were still never quite right though, too bright. I came to suspect that the ceramic caps I used as part of the recap could be part of the problem.

I figured this may be the case due to an effect that MLCCs have where the capacitance can apparently drop when they get close to their rated voltage. This apparently doesn’t play well with LCDs sometimes.

I swapped the 5 MLCCs out for tantalum caps last night and noticed a definite improvement. It still takes around 30 seconds to fade to normal, but after a lot of trial and error with the adjustment pots, the picture looks pretty good, with a couple of slight imperfections. It’s definitely good enough for me though.