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My PowerBook 100 is alive again!

twelvetone12

Well-known member
I've been lurking around here for a bit gathering info on how to repair a PuwerBook 100 with a blank screen, and I'm happy to report it was a success!
The powerbook 100 was my first laptop back in 98/99 when I was a kid. It was given to me for free by a dealer since the screen would intermittently shut down, the typical black screen of death on these machines. Nevertheless I dragged it around with me, and since it was missing the internal drive, I used a (huge) HD SC 20 that came with my Mac Plus, which weights a ton (yes I was young and dumb). I still have the drive, a project to fix it is for the future.
Eventually the screen died completely and since at the time I know nothing about electronics I sold off mine. But I really loved that machine!
So I decided it was time to get one and properly fix it, since now I actually understand what is going on in it. I got a very cheap and broken unit off ebay (gosh are these expensive!) to play with.
Well turns out a simple recap did the trick, I still need to properly verify the voltages in the buck converter for the screen, and I have to recap the screen still, but it powers up like a charm! I'm so happy.
...and sound does not work anymore (it did BONG when it had the black), that is for another debugging session.

Does anybody have the schematic for the screen? I found the schematics for the logic board but all the screen assembly is missing. Before just changing the caps there I would like to figure out exactly what they are for.
Now I need to get one of those rebuilt batteries...
 

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3lectr1cPPC

Well-known member
That screen looks remarkably good for one with original caps on it still. Please get them changed ASAP! Using the screen with the old caps installed will accelerate corrosion and damage.
There won’t be any schematics for the screen as Sharp made the screen, not apple. Out of curiosity why do you want to know what the caps were exactly doing?

They should be replaced with new electrolytic or tantalum capacitors. I’d recommend tantalum. Do not use ceramic capacitors. Their capacitance changes as they get close to their maximum rated voltage, which can cause contrast drifting when used on LCD screens.

I do believe the caps are used to control contrast of the screen in some way, but I don’t know anything more specific then that.
 

twelvetone12

Well-known member
I don't like to just change components without actually knowing what the circuit they are in does :) It also helps me debug further if (when) stuff does not work.
I already have all the replacement tants, next step is display and inverter!
 
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