Hey everyone, I have a question about my powerbook 140 that I got online. When I plug it in and turn it on, I hear the chime and the screen lights up but remains black. The hard disk drive starts to whir and it does that for thirty seconds or so, then stops. Then it starts whirring again for thirty more seconds, then stops. I've also played with the contrast and it just remains a lit black screen. I even replaced the LCD and the results were the exact same. Someone please help, thanks!
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Powerbook 140 not booting
- Thread starter Whereisammo?
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@MacTech68 would be able to provide some insight. He is knowledgeable with older 68K Macs like this model.
You rang?
The 100 series PowerBooks can be a pain to service & diagnose, and whilst I can tell you about faults I'm aware of, there are some due to their advanced age I may NOT be aware of.
First a warning - the cable attached to the "Interconnect Board" uses single stranded copper wire. Flexing this cable only a few times can break the copper strands, rendering it useless. This is the cable that must be disconnected at the rear of the machine to separate the two halves of the machine.
Be careful when removing and re-fitting screws. These machines have brass threaded inserts molded into the plastic housings. Sadly, the plastic surrounding many of them would begin to crack and finally break away. I would usually apply a small amount of superglue to the cracks (avoiding the thread). If they fell apart completely, you could get the pieces and re-assemble them, tightly, and build up some resin around it to hold them.
Be sure to check the output of the AC Adapter is between 7.5 and 7.9 volts when un-loaded.
Be very careful of any thin, flat, copper colored cable. These "flexible PCBs" can be easily torn if force is applied across them. These would often snag at the hinges (clutches), and tear, which would then create shorts via the metal hinge causing all sorts of weirdness. This occurred when the display housing would come apart due to the brass threaded inserts breaking (as described above).
There was an early problem which was due to the display cable not being quite thick enough to make contact in the LCD's connector - resolved by adding a shim on the cable. It's unlikely that any of these original cables exist without already having a shim.
Now that I've scared you, it's time for the worst stuff.
It would seem that one cause of your symptom on these machines as they've aged is leaking capacitors in the LCD display assembly itself. Replacing these is a delicate operation. There are circuit boards around the edge of the glass and these connect to the glass display via several multi-contact cables. These are very delicate especially where they connect to the board and especially at the glass. If you rip, tear or disturb these, your display is toast. The result will be a horizontal or vertical line (or multiple lines creating a band) on your display.
There is video showing what needs to be done, however, there were more than one model of these displays.
I remember adding this shim to many of the Powerbooks we sold in that time frame. Thanks to a trip down memory lane