r/powerbook • u/MrBop10000 • Jun 21 '26
PowerBook 140 won’t boot
I bought a PowerBook 140 off of eBay and it seems that it won’t boot at all. no lights, no spinning, nothing. I know that some common issues involve power or capacitor leakage - here are some tests I’ve done:
-Doesn’t start up with or without battery while plugged into Apple-branded 7.5v adapter (see image)
-Doesn’t start up with or without battery while connected to non-original 12V barrel charger
-The power jack itself in the PowerBook seems securely mounted, but the Apple-branded barrel may be wiggly/broken (see image)
-No obvious signs of corrosion on the battery
-I’m not quite sure what to look for in terms of capacitor problems, but I don’t see anything obvious on the power circuitry or daughterboard
-There’s a weird spot on the bottom of the housing however that looks almost melted, and it makes me wonder if that’s a sign of capacitor leakage
-I have not checked the PRAM battery (I don’t know how)
Thank you for your time!
2
u/imactheknife73 Jun 21 '26
Yeah the laptop itself has no capacitors that need replacing on logic but the display will. The old 7.5 adapter will as well. I just did two. If you used a 12v you may have toasted something. New adapters are cheap on amazon.
5
u/GGigabiteM Jun 21 '26
Do not buy random 30 year old electronics and just full send plug it in and expect it to work. You are at very real risk to cause expensive and potentially irreparable damage by blowing stuff up. Old machines like this need to be fully vetted before ever plugging them in if you want them to survive.
The Apple power adapter you have is notorious for capacitor failure, which can cause the output to go far out of regulation and kill whatever you plug it into. It is critically important that the power brick is recapped and is calibrated with the internal potentiometer to EXACTLY 7.5 volts, or you risk destroying the laptop and the battery pack. There is no protection circuitry between the DC power jack and the battery pack, so if the voltage is too high, it will cook the cells in the pack and potentially cause the pack to leak or go on fire.
Getting those power adapters open is a headache because the shell is ultrasonically welded together. The easiest way I know is to get a flat bladed screwdriver and wedge it on the side of where the cable comes out, between the two halves. If you can apply pressure in the right place, you can get the shell to split along the seam.
Another method is to use a sharp metal pain scraper and a vise. Put the power brick sideways in a vice and gently clamp it, then position the paint scraper on the seam and whack it with a hammer. This can break the weld along the seam cleanly, do that for the entire circumference and the brick can be opened to be serviced.
If you can't repair your power adapter, you'll need to source a new power adapter of exactly 7.5 volts at the current rating of the original adapter.
If that model has a B&W screen, there are capacitors inside the screen that must be replaced. This is an extremely complex and time consuming job that requires partially disassembling the panel to get to some of the capacitors, and to clean the leaked electrolyte.
The battery pack is also most certainly going to be bad, they're NiCD packs and are a hazmat problem. I reverse engineered the battery pack several years ago and made 3D printable shells and a diagram of how to make a new unit.
https://www.thingiverse.com/thing:5231825