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PowerBook Duo 270c Restoration


New member

my beloved 270c just died and I consider an attempt of restoration including re-cap. Fotos of suspected faulty areas attached.

Can somebody please help with an evaluation for the chance of success and the specs/ details of the required electronic parts?

I have not yet disassembled the display - are there more parts which should be replaced?



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Well-known member
Hello, and welcome to the forum.

It looks like a few components have failed, hard to say why or how that's happened (I am not super familiar with these I'm afraid).

It all depends on how much time and energy you want to put into trying to save it. Most of the components have markings/ratings on them, so just follow that to find the replacement. As for the burnt/dead capacitor in photo 3, it's a ceramic capacitor and it's probably of a low value similar or the same as the one below it - you could measure C225 out of circuit and go from there.


New member
Thanks! As for C82 (photo 2): is that one eventually missing (by intend)? Looking for a photo of an intact 270c board... Are detailed circuit diagrams somewhere available? Would it work to replace the board with one from a 230 (I also have) - or just swap the displays between 230 and 270c...?? :)


Well-known member
Just looking at the Service Source I think it would be unlikely that the displays or boards could be swapped, if I am understanding your question correctly. The display cables for each are significantly different. Its hard to predict how possible a repair would be for this board, but some of the folks here have brought some boards back to life that I would have thought were unsalvable. Your board looks like it could be fixed by replacing a few components (along with eliminating whatever initially cased the issue) and largely comes down to your skill level, or how much time that you want to invest. If I can find any more information, I will pass it along.


Well-known member
Has this machine been in a particularly humid environment, or had anything spilled on it? I'm seeing an awful lot of corrosion, but not much outright leakage from electrolytic caps (at least, in the photos posted). Yet. The caps will - sooner or later - leak. They always do.

If any custom chips have been damaged, you would need a parts donor machine from which to extract a working replacement chip. Otherwise, the motherboard itself may be fixable; high-resolution photos of both sides of the entire board would help in making an overall assessment.

If the display has been damaged, you would need to get one from a donor machine.

Generally speaking, this machine needs a full capacitor replacement, several damaged pins replaced, and at least one MLCC capacitor has exploded (probbably caused by, and still causing, a short from a power rail to ground). Also, the board needs to be cleaned; residue from

Note that I'm just going on accumulated electronics knowledge; the last time I had a Duo 270c in my possession it was still quite new, and didn't even belong to me (was provided for work).

P.s. - even if you decide not to attempt a repair (or are unsuccessful), you may be able to sell it as a parts donor machine. If the case, keyboard, and trackball are in good shape, it might even be useful for a Raspberry Pi conversion project.


New member
I used this device regularly (since 1995) in the same clean home environment (mainly as a midi sequencer), usually always on/ sleeping. The last thing I did (in March) was to install SetDate to fix the Mac OS 7.6.1 Y2k20 date bug :). The nice color display always worked fine. The machine has max. RAM (32MB) and (since many years) a silent PowerMaster II CF. Btw. I also have most of the peripherals (Floppy, Mini/Dock, PowerCD etc.) - love this old stuff ;-). I suppose the elcos already leaked which caused the burnt ceramic. Attached is a photo I took before I initially cleaned it. Still wondering if C80 (not 82) fell apart/ disappeared (probably) or never was there...


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Well-known member
Hey, anyone has a list of all PB Duo 270c capacitors?
Does the LCD on it also needs a recap?

Thanks, M.


Well-known member
pics 2,3,5,6 show some serious damage, I wonder how that happened, maybe a short somewhere and then second failures..
water damage?
I would carefully scratch off that burnt residue off the chips and give it all a good clean with IPA and a soft toothbrush and then go on from that, also cleaning the corroded tiny vias..
here is a good reference site with photos from a Duo 230:


Well-known member
Well I got the 270c yesterday and is uses bit different array of caps:
Here is the list:

Logic board:
4x 35V 100uF 10x10mm footprint
1x 35V 47uF 8x8mm footprint
1x 25V 100uF 8x8mm footprint
All those must be 10-11 mm tall or less

1x 25V 33uF 6x6mm footprint, 6mm tall

1x 35V 10uF

LCD has an array of capacitors also, but they all looked perfect, and heating the pad with the soldering iron produced none of the usual fishy smells...

But if someone needs a list of them:
(Sharp LQ9D041 LCD)
6x 47uF 6V
2x 22uF 10V
3x 100uF 6V
1x 10uF 25V
1x 47uF 16V
1x 10uF 16V
1x 33uF 10V

I disassembled it before I powered it on, and also replaced a leaky 10uF 35V cap on inverter with new. Actually I used 3x 4.7uF 50V MLC caps in parallel as I have hundreds of them, and that gives about 11-12uF of capacitance (measured beforehand), and extremely good and low ESR. The capacitance of MLCCs is usually bit on the lower side and also decreases a bit with applied voltage. And those will never go bad.


Also one note, the hinges looked they were coated with some kind of white grease at some point. That stuff was quite hard and lost all of the greasiness. I decided to clean them in an acetone and some carb cleaner, and reapply some white Molycote grease.

Other capacitors on the logic board are also starting to leak a tiny bit as expected, but I had to look twice to be sure, as the leakage is really minor. I don't have exact replacements for those on hand, so I will order them and do them next time. I will leave the LCD capacitors alone for now, the image is perfect.

I was lucky as the my new PB 270c is fully working, despite sitting for the last 20-25 years or so the previous owner claimed. I don't know how, but the original Apple NiMH battery was still at 6.8V before I even first plugged it in, and I charged it for about 30 minutes and then tested it for few minutes and it held. Also the HD sounds perfect.

I only need to find an original charger now, as I was using one from the PB G3


Well-known member
I was lucky as the my new PB 270c is fully working, despite sitting for the last 20-25 years or so the previous owner claimed. I don't know how, but the original Apple NiMH battery was still at 6.8V before I even first plugged it in, and I charged it for about 30 minutes and then tested it for few minutes and it held. Also the HD sounds perfect.
That's incredibly rare, surprising! Most every one of those have leaked at this point.

This cap list and photos are incredibly helpful. We didn't previously have a full cap list for the 270c.
I run a website that among other things, has a large collection of capacitor reference values and photos: https://www.macdat.net/cap_reference.html
You'll notice that the 270c is missing from my list.
Would you mind if I used your photos on my site? I will be sure to credit them to you. It would really help me out!

I'd also recommend replacing the LCD caps, even if they're ok for now. That many right next to those fragile LCD ribbons is gonna be bad news when they do leak.



Well-known member
Hey, yeah, go ahead. You can use the photos and the cap list :)
I am also planning of opening a dedicated new thread and presenting the restoration there.
Btw, I ordered Aluminum Hybrid Polymer Capacitors, as they are more like standard electrolytics, but have excellent electrical properties. Also they are like 1/3 of the price. I can also give you exact P/Ns of them (ordered of Mouser)...


Well-known member
Thank you very much! Polymers are great from all I've heard. I think I've used them in some places before. I mostly go with what fits best, most of the time.


Well-known member
Yes, all my surface mount electrolytic cap replacements are polymers that have the original look to them. Great things that won’t leak.


Well-known member
Yes. The 180c from one year prior to your 270c is infamous for it. Mine had leaked all over the place. @jmacz can also attest to how bad caps can affect a 540c screen, from the same year as your Duo. All these are Sharp LCDs.
More than anything though, they're the same exact caps that leaked on your motherboard, and they're 29 years old. You'll thank yourself later if you do yours now before they've leaked!


Well-known member
I did not find that the caps had leaked yet on my Sharp display (540c) but replacing them definitely correct strange ghosting/shadows/bleeding that I saw in the display.