Top half of PowerBook passive matrix LCD gone dark after recap

[luRaichu]

I just recapped a Sharp passive matrix display from a PowerBook 160, it worked fine for the first hour but then the top half of the screen started flickering and went dark. If I crank the contrast I can see the top half flickering in darkness.
I think it could be a bad connection with one of the display ribbons (as highlighted). But before taking the whole display panel apart again I want to know if someone has fixed this before.
(Second video shows display flickering, please don't watch if you're photosensitive. Thanks)

 

[croissantking]

FREE KEVIN

 

[croissantking]

Also I don’t think it’s an issue with the display connector highlighted, as this would cause a more localised issue whereas you’ve lost half the screen. More likely to be a bad trace or via caused by cap leakage.

 

[luRaichu]

More likely to be a bad trace or via caused by cap leakage.

Where? Why would the problem progress, instead of being apparent right away?

 

[luRaichu]

I have the panel stripped apart on the bench right now, the top half of the picture is coming in and out intermittently. Often it'll start out dark, flicker back to normal, then flicker to dark again. You don't know how upset I am

 

[3lectr1cPPC]

I have the panel stripped apart on the bench right now, the top half of the picture is coming in and out intermittently. Often it'll start out dark, flicker back to normal, then flicker to dark again. You don't know how upset I am

2 things to check.
First, the display cable is pretty tricky to fully reinsert into the connector and easily comes loose. Make sure you aren’t chasing the wrong problem.
Second, shine a flashlight up to the ribbons around the screen with the integrated driver ICs. Check for any dark spots (corrosion). If you see dark spots in any of the ribbons near those caps, and if the display cable isn’t loose, then unfortunately that’s pretty much the end for one of these LCDs.

 

[croissantking]

Where? Why would the problem progress, instead of being apparent right away?

What I meant was that it seems like it’s something other than the ribbon cable you highlighted, because a localised failure there wouldn’t cause half the screen to cut out.

This is what I would expect to see:



I feel your pain because I’ve had to go through exactly 4 of these panels in order to get a non-faulty one.

 

[3lectr1cPPC]

What I meant was that it seems like it’s something other than the ribbon cable you highlighted, because a localised failure there wouldn’t cause half the screen to cut out.

This is what I would expect to see:

View attachment 91213

I feel your pain because I’ve had to go through exactly 4 of these panels in order to get a non-faulty one.

That's what you get if one of the vertical ribbons is bad, but the horizontal ones can absolutely take out half the screen. You see this all the time on the PowerBook 100.
Could also be a bad trace though.

 

[croissantking]

That's what you get if one of the vertical ribbons is bad, but the horizontal ones can absolutely take out half the screen. You see this all the time on the PowerBook 100.
Could also be a bad trace though.

Yes, but OP had highlighted one of the vertical ribbons, so I was just responding to that hypothesis.
I didn't know the horizontal ribbons could take out half the screen - interesting.

 

[3lectr1cPPC]

Yes, but OP had highlighted one of the vertical ribbons, so I was just responding to that hypothesis.
I didn't know the horizontal ribbons could take out half the screen - interesting.

Yeah, if the top two aren’t working then about half the screen will go out. I’m thinking in this case though that it’s probably more likely a loose or damaged display cable, or an intermittent trace perhaps.

 

[luRaichu]

I tried reseating the display cable from both ends with no effect. If there's a tear it's not in any portion I can see, I'd have to pull the entire thing out

 

[luRaichu]

I have my next display panel... What's the best way to desolder the tantalum caps from the first panel so they can be soldered to the new panel

 

[finkmac]

the best way is to buy new caps

second best way is to use desoldering braid.

or you could do what i do. heat up both sides repeatedly and slowly use iron to angle the cap upwards until one side isn't soldered down.. then finish the job with the iron on the other side. ymmv.

 

[croissantking]

or you could do what i do. heat up both sides repeatedly and slowly use iron to angle the cap upwards until one side isn't soldered down.. then finish the job with the iron on the other side. ymmv.

Yeah I do this and it’s fine if the PCB isn’t being re-used.

I also use two soldering irons sometimes.

 

[finkmac]

I also use two soldering irons sometimes.

like chopsticks

 

[luRaichu]

I recapped a second display with tantalum caps taken back from the first. It's not an improvement.
(this display somehow has a chip in its glass, on the southwest corner)
I tested this display in two 160s with the same result.
Please, let me know if you have a tested, working passive matrix display panel for sale. I'm done playing games