PowerBook 165 screen issues after a recap

[pezter22]

I have a similar issue that is mentioned in the PowerBook 140 Display Blue posted by Powerbook27364 recently.

I've successfully recapped several PB screens, but this one is bugging me. At first I got a full display but the top half was broken and dithered. I went back cleaned everything (again), removed capacitors (I used ceramic) to measure them again. Reinstalled the screen and had the same issue.

Days later this time I replaced the resistors, removed the 22uf and 100uf capacitors to measure and clean, I also checked with a multimeter in continuity mode the ribbon connectors with the pins along the edge of the screen, all were good. I removed and cleaned the DC/DC Converter board.

However, when I reinstalled the screen I got the same blank screen that was mentioned in the previous post about the PB140.

I am at a loss with this screen. I have several PB165 that I successfully recapped with ceramic 3.3uf capacitors without issue. Tthis one is just being a pain.

Any suggestions would be greatly appreciated. I'll go back and check the 22uf and 100uf traces.

 

[Cedsrepairs]

Exact same problem for me, but on a 145 (which is rouggly the same)

Fully recapped as well, worked fine for a year, now half of the screen with similar patterns as yours

I think that some cap juice has made its way inside a microscopic via and destroyed the copper...

 

[3lectr1cPPC]

I think that is or can be caused by a loose display cable. That or something similar has happened on my 145 when the cable was loose.

 

[Shaddam IV]

Have you tried mounting the screen on a different chassis? I had a screen that appeared half broken (top half with stripes). After I‘d swapped the mother- and daugherboards (from another 160), the screen worked just fine.

 

[Cedsrepairs]

You give me hope . I took the screen apart again but didn’t really check the motherboard connector .
I did this repair with my teenage daughter so it’s a pain to see it not working anymore

It’s worth a try

 

[Cedsrepairs]

Well the goods news is : it's is mostly working, kinda.

Indeed as I suspected, my problem of the entire bottom half of the screen basically missing one white column on two, was a via problem.
Some vias close the the bottom of the board (next to the soft board interconnect) have been filled with capacitor juice, and this has slowly eaten the via, despite that unit beeing recapped since 2 years.

I narrowed it down to the via leading to the fourth row of pins of the interconnect (starting from the right) was not making contact. And I was lucky enough for this via to be connecting the top layer to the lower layer, because this seems like a 3 layer board to me, clearly some via go "inside" the board

Somewhere around here;


Now with the repaired vias (I put a wire in them and soldered both sides) : it works

But a small and super weird problem remains ; I could not screw the screen back in place properly. Each time I put the two screws on the right, the screws tightening it to the plastic frame of the Mac, the screen stops working ( image gets satured in white ).
Even putting the screw half way, and touching it with a screwdriver touching the metal frame, makes the screen bug. It makes no sense at all as this screw simply touches the frame and plastic, nothing else...
I have no idea what is causing this. Pushing the frame does not create the problem. It's super bizarre. Maybe the screws got magnetized and the metal frame doesn't like this (as I use a magnetized mat to store the screw, and a magnetized screwdriver). But if it's that they are BARELY magnetized. Or it may be something completely unrelated. Idk.

I decided to live with it, and simply put the two screws on the left (on the backlight side, it's fully plastic).

I'm reinstalling 7.5.3 as I'm typing.

 

[Shaddam IV]

Congrats!

 

[Cedsrepairs]

This board was cleaned with IPA before I recapped it, but I didn't pay much attention to the vias, and they probably "stored" tiny amounts of capacitor juice that slowly killed them AFTER my repair.

Lesson learned for next time ; inspect the board with the microscope and "clean" as much as possible the inner hole of each via close to capacitor juice. I'll make sure from now on that I can at least see thru all vias.

 

[Shaddam IV]

Help please: What is a "via"?

 

[Cedsrepairs]

A via is a tiny hole in a multi layer circuit board connecting the top side with the bottom side



Or, as is the case here, some board are even multi layered (more than just the top and the bottom that you can see, but also circuits sandwiched inside the board, usually 4 or 6 layers - in this particular Powerbook 145 screen board I was talling about ; I think it's 3 layers)

Here's an example of a side view of a 4 layers (of copper) board. This is typical for anything from the Nineties.



And as an amateur, you basically can only repair vias that connect the top layer to the bottom one.

You can forget about repairing so called "blind vias"

Which is also why repairing laptops (and modern desktops) can come to a dead end, unlike repairing desktops from the 80s that you can repair with a hammer, have a single or dual layer board with confortbale spacing, and only use "off the shelf" components.

 

[Shaddam IV]

Thanks! That makes it very clear.

 

[pezter22]

Well the goods news is : it's is mostly working, kinda.

Indeed as I suspected, my problem of the entire bottom half of the screen basically missing one white column on two, was a via problem.
Some vias close the the bottom of the board (next to the soft board interconnect) have been filled with capacitor juice, and this has slowly eaten the via, despite that unit beeing recapped since 2 years.

I narrowed it down to the via leading to the fourth row of pins of the interconnect (starting from the right) was not making contact. And I was lucky enough for this via to be connecting the top layer to the lower layer, because this seems like a 3 layer board to me, clearly some via go "inside" the board

Somewhere around here;
View attachment 70344

Now with the repaired vias (I put a wire in them and soldered both sides) : it works

But a small and super weird problem remains ; I could not screw the screen back in place properly. Each time I put the two screws on the right, the screws tightening it to the plastic frame of the Mac, the screen stops working ( image gets satured in white ).
Even putting the screw half way, and touching it with a screwdriver touching the metal frame, makes the screen bug. It makes no sense at all as this screw simply touches the frame and plastic, nothing else...
I have no idea what is causing this. Pushing the frame does not create the problem. It's super bizarre. Maybe the screws got magnetized and the metal frame doesn't like this (as I use a magnetized mat to store the screw, and a magnetized screwdriver). But if it's that they are BARELY magnetized. Or it may be something completely unrelated. Idk.

I decided to live with it, and simply put the two screws on the left (on the backlight side, it's fully plastic).

I'm reinstalling 7.5.3 as I'm typing.

This gives me new hope. I put the PowerBook aside because of the frustration. I will take a look at the vias this week. Thank you for the assist.