PowerBook 180c screen tints yellowish

[awulf]

I finally got around to fixing a PowerBook 180c that had a broken hinge mount and broken ribbon cable. After a couple years on the look out for a new ribbon cable have ended up fixing the ribbon cable by bypassing 4 of the wires in the ribbon cable were severed with some individual wires. Also have recapped the screen and inverter board since it was smelling super fishy, especially when turned on.

The PowerBook is all operational, the LCD is displaying everything correctly with no weird artefacts, back light is looking good. But the screen becomes yellow when displaying dark objects on the screen. Have attached photos showing

1. Mostly black screen, where the whole screen turns yellow.
   
2. Partially black screen, where the scroll bar turns yellow.
   
3. Mostly white screen, where no yellowing is happening at all. 
   

If I poke the ribbon cable (or even get very close to the ribbon cable) with my finger they yellowing situation changes (more or less comes up). This doesn't happen if I poke it with some other object, which leads me thinking it might be some sort of capacitance issue? The severity of the yellowing also improved after washing the PCBs around the LCD to make sure all the capacitor goo has been washed off. I don't see any corrosion going on.

Maybe replacing the capacitors has changed some properties and the LCD needs to be tuned again? I'm thinking this because there are 5 trim pots to the left of the screen labelled "V2", "V5", "V7", "VcDC", "Shadow" & "VcAC", but I don't want to touch them until I know what they do.

Anyone got any ideas?

Thanks

 

[techknight]

Looks like one of the blue data bits to the LCD panel is still intermittent.

 

[awulf]

Thanks that must be it, looking at the data sheet for the LCD the following wires are broken on the ribbon cable.

12 - GND

13 - B0 - BLUE Data Signal (LSB)

14 - B1 - BLUE Data Signal

15 - B2 - BLUE Data Signal (MSB) 

I guess the patch (attached photo) isn't adequate enough. Probably too much noise/interference. Need to think of some other way to fix, make a new cable or keep searching for one. At least it's mostly working at the moment.

 

[techknight]

Yea, your going to need a new cable sadly.