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PowerBook 145: No contrast AFTER recap

3lectr1cPPC

Well-known member
So, I bought a PowerBook 145 off of eBay, described as having no contrast on the display. It arrived, and so did the caps I ordered so that I could get it going.

I did the recap last night, (my first real SMD rework attempt), and I think the work turned out fine, although it doesn’t look very pretty. I did all the tiny caps with ceramics, and then I replaced the bigger ones as well. (I used a single tantalum and an axial electrolytic bent to fit. I mean, it’s an odd assortment but it should work, right?)

I cleaned up the pads and there didn’t appear to be any major damage. The pads pretty much all had some minor damage around the edges, but each one took solder and I was able to get every new cap installed. After all of this, I plugged everything in, and still no contrast! Does anyone know what’s up?

One thing I’m concerned about is how small the replacement caps were. I was able to install them just fine, but I’m worried something could have gone wrong and I got the wrong type.
Here’s some images of my work:
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A1E3C7A3-5D08-42D5-ADE1-242E9D35D939.jpeg


EA8DF243-0DEE-4F3F-9633-47B43FA31377.jpeg
 

mdeverhart

Well-known member
Do you have any pictures of the display on that show the issue? Is it the whole screen, or just sections?

It looks like there’s a LOT of cap goo and corrosion around the components near the caps - JP1, IC2, etc. Shorts from that conductive goo (between pins, especially the fine pitched ones) might be the issue. Unfortunately, the goo will wick through the vias to the other side of the board, causing shorts there as well. It can also get under the flex cables that connect from the driver boards to the LCD.

I’d try to clean up the goo as well as you can with IPA and cotton swabs, or a soft toothbrush around the ICs. If it’s under the flex cables it’s going to be hard to get out. I was able to thread a piece of cotton string between the flex cable and the PCB, using a piece of a drinking straw as a “needle” to pull it under (I wanted something thin, flexible but with some rigidity, that wouldn’t accidentally pierce or scrape anything). Once I got the string under, I added some IPA and carefully flossed underneath the flex cable with the IPA.

Try not to get so much IPA on the board or cables that it wicks over to the LCD. You definitely don’t want it to get between the display layers, and I’m not sure what it will do to the LCD in general.
 

3lectr1cPPC

Well-known member
I believe a lot of what your seeing is flux - I didn’t see much liquid cap goo before recapping, mostly just crusty corrosion. I’ll give the whole board a really good clean though and see if that helps.

to answer your question about what I’m seeing on screen, the entire display shows minimum “black screen” contrast, just as you’d see with one that hasn’t had any work done yet. Adjusting the contrast slider has zero effect.
 

mdeverhart

Well-known member
Ah, gotcha. On my Duo the cap goo caused a section of the screen to be basically totally white, but I’m not familiar with the “no contrast, black screen” effect you’re seeing.

It seems like a good cleaning would be a good idea. If you’re seeing corrosion on pins it seems likely that there were leaks at some point. There could be additionally goo/corrosion under the ICs as well.
 

3lectr1cPPC

Well-known member
I didn’t see any liquid goo, and the leak didn’t seem that bad in general. It’s certainly possible that there is some lurking under ICs, but if that’s the case, I don’t have the skills to remove them. It’s worth noting that I haven’t recapped the inverter board (if that’s separate on these, is it in the top case by the cluster of PCBs above the keyboard?), but I haven’t ever seen what caps they have. As long as they aren’t SMD electrolytics, they’re probably still fine. The seller also claimed that the laptop worked when it was tested with a working screen, so I doubt the issue is on the laptop itself. I’ve done a thorough cleaning of the board and I’m going to test it again, so I’ll give an update when that’s done. Thanks for the help!
 

3lectr1cPPC

Well-known member
It’s ALIVE! Cleaning it up did the trick! My first successful Mac recap! Thanks for the advice on cleaning it @mdeverhart!
0CCE4729-7CE7-49E3-B0F8-144D13DCD34E.jpeg
Now, on to the next challenge: the trackball isn’t working. I believe the seller said it worked when they tested, so it probably came disconnected while I was working on it.
 

3lectr1cPPC

Well-known member
Thanks! It still needs a lot of work to get fully working, but I’m just glad the hardest part is out of the way.
 

desertrout

Well-known member
Nice work! Are those ceramics you're using for the small 3.3uF's?

It’s worth noting that I haven’t recapped the inverter board (if that’s separate on these, is it in the top case by the cluster of PCBs above the keyboard?), but I haven’t ever seen what caps they have. As long as they aren’t SMD electrolytics, they’re probably still fine.
I was going to say before your latest post that this may have been the culprit, as there are two radial electrolytic caps that can leak and affect brightness and contrast behaviour... but @mdeverhart 's keen eye obviously spotted the real issue.

So, yes it's tucked up in the top case next to the battery and speaker --- two screws, pull up to disconnect it from the interconnect board, and unplug the backlight cable. The two caps are next to each other against the contrast slider. I think C1 is a 33uF / 10V, and C4 is 47uF / 16V:

Screen Shot 2022-01-01 at 3.09.00 PM.png
 

3lectr1cPPC

Well-known member
Nice work! Are those ceramics you're using for the small 3.3uF's?
Thanks, and yes!

I was going to say before your latest post that this may have been the culprit, as there are two radial electrolytic caps that can leak and affect brightness and contrast behaviour...
I'll check on them next time I have the 145 apart. I'm waiting for now because the hinge standoffs are so badly screwed (haha), that I'm not daring to close the screen again until I've got new 3D-Printed ones installed. I'm planning on replacing them ASAP.
 

Spode

Active member
Not wanting to hi-jack a thread, but it seems very on-topic. I also recapped a 145 screen. It seems fine, but I will admit, moving the contrast doesn't really change much at all until I go all the way to the end - pretty binary. Should there be a noticeable difference? The contrast itself looks great to me, so I've not been worried that I can't change it.
 

3lectr1cPPC

Well-known member
What type of capacitors did you use to replace the old ones? My contrast slider is definitely more sensitive than that. Moving it just slightly produces a noticeable change.
 

Spode

Active member
I tried that too. I'm not all that fussed about fixing at this point (unless I open it up again), but it's useful to know that is not intended behaviour. If you get a moment at some point, perhaps upload a short video of how it should look going from max to min?
 
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