Have a question...
Let's say that you have a Powerbook 100 that your boss just discovered he had hidden in a closet in his house that his wife had packed away five years ago because it was acting up and he decided to give it to you one day because you are the staff Mac-head. You get the machine, and pretty much know that the PRAM batteries are probably shot. You replace them, and the machine still won't boot properly. The screen comes up a dark blue. You get the chime, you can hear the hard drive power-up, but screen stays dark. Whenever you use the reset button and restart, there is, for a brief instant, an image of a right, proper Mac screen. You've tried to do the PMU reset to no avail.
Any thoughts? Just speaking, hypothetically (been a weird week)...
Rob
I own a PB100, and I ocasionally use it. Sometimes, it boots with the screen dark, although the HD spins up. I've found that pressing both the reset buttons on the side at the same time a few times tends to fix the problem. Also, try booting by pressing the spacebar.
Perhaps the screen brightness and contrast are set to the extremes. It's really annoying when this happens because you can't tell whether it's the former problem or it just isn't bright enough. Try centering the dials?
I have one exectly like that, It only displays a dark blue screen. I have determined the problem to be 8 or so leaked capacitors on the back of the LCD, but I have not yet had time to get them replaced. Mine is also missing the lead connecting the brightness/contrast board to the multiple connectered board…
I opened up the lil' PB (an easy chore, even if I did strip one of the plastic screen cover's screws), removed the screen, and turned the screen over. I take it that the caps are the little square ones located on the bottom left (when turned to face screen forward) side? There is definitely leakage on the lower tier, left (when looking at the back).
Anyone know a source for spares?
Incidentally, this is the easiest Powerbook I've ever worked on, far easier than my old PB150. My (currently dead) Portable is easier, though not in the same class.
This thread shoud be of some help for the type of caps to get.
http://www.applefritter.com/node/6839
Do they have to be electrolytics? Reason being is that these bad boys are hard to find; can't even find them at Mouser. Any thoughts?
I usually replace like with like to avoid any issues. If you can't find there anywhere you could try other sorts as long as they are polarized, but don't blame me if it doesn't work.
I did this test with 3 logic board and one known good LCD:
results:
a_known good LCD + bad MoBo 1 = no backlit
b_known good LCD + bad MoBo 2 = no desktop & contrast at max level (the dark blue thing that you linked to bad capacitors on the LCD)
c_known good LCD + bad MoBo 3 = the PB starts up as soon the adaptor is plugged and then have the symptoms of MoBo 2.
Did any of you sorted things out replacing the capacitors. Should we investigate further the logic board issues?
Ben
Hey,
I got a PB100 recently. Worked fine, except the power connector was loose causing the machine to cutoff. So . . . I opened it up (and yes they are the easiest to work on) and resoldered the connector. I did not burn anything else. Now, I get the blue screen, no chime, no nada but coma enchilada. Ergo: good LCD + good mobo + light and fresh air = a dead witch under the porch.
I re-opened my PB100 and looked, this time, at everything. There is still evidence of leakage on those caps, but now I can't help but wonder about those two caps near the LCD connect on the logic board. Lacking a way to test them, wondering is all I can do, for the moment... but sealed caps do fail. It may be possible that not one but a multitude of problems are the issue here, and all it takes is... the... right... nudge.
Does anybody know of a way of testing capacitors without taking them out and sticking them in a circuit that's definatly working??
cheers,
Joel
... well I managed to find these caps and replaced them: same thing. Not only! I also tested the LoBo without those caps... same thing.
In the meanwhile I bought a lot of old PBs 100. Most of them don'even start up, but one of them has another weird behavior: contrast okay, britghness okay but at max level (impossibe to dim).
Although I don't recall if the brightness controll become active during the boot (these testing are performed without the HD (to sped up the procedure).
Will keep you posted.
Ben
on the mobo that causes the screen to stay at max brighteness level I can dim the LCD via the system 6.0.8 control "portable", that has a specific control for the "contrast", that on the PB 100 changes the brigtness. I desoldered both caps: same thing. So neither those two caps close to the LCD connect.
Is it so difficult to find the PB 100 MoBo circuit design?
Ben
Apple has never released MLB schematics.* You'll have to trace out the board yourself.
* There may be schematics out there for some early Macs (incl. the 128-Plus), but IIRC those were done by third parties.
dan k
... well, actually I was wondering if someone had done that!
Ben
I finially found a good LoBo to fix my original PB 100. At that time (Summer 1992), although the price had been greatly reduced (1200 USD) still was a serious investment!
BTW. anybody has got any more info on the PB 100 LoBo?
Ben
Ben:
I have some miscelaneous Powerbook parts that I'm offering for sale. I have some logic boards, processor boards, RAM modules, power supplies, screens, trackball assemblies, internal floppy drives, screen control boards, and keyboards.
If you're looking for anything specific for the 1x0 series Powerbooks, send me a PM or email me at managed_resistance@cogeco.ca
I have tested 10 LoBo with 10 displays and to my surprise some combinations work. So it must be that bad but not dead capacitors in the display must be helped by a good LoBo and the other way round.
Anybody has some more new on this matter?
Ben
I replaced all 8 caps but still get the dark blue symptom. I replaced the inverter board and some caps on the lobo, but still after 2-3 days the syndrome comes back,
Othe ideas?
Ben
I did a terrific experiment: replaced all caps with leakage signs one by one and rstarter the PB. ***the dark blue syndrome is caused by the cap closer to trackball socket!
Will post pictures tonight,
Ben
I am in quarantine as most of the citizens, so I decided to give another try to my bunch of busted PBs 100, to speed up the testing I would like to know if are there power on pads on the logic board to avod the hassle of reinserting the keyboard flats?