PowerBook Duo 250 won't start

[mbaran]

Just received my FREE Duo 250 from BMOW and he said last time he used it, it worked fine.

I grabbed a tested Duo charger off eBay, but I cannot for the life of me get it to turn on. Will it not function without a working battery? I am running it battery-less.

When I plug in the charger I get +24v give or take at the + and - battery charging pins. Over the course of the next minute or two, the voltage will slowly drop to 0v. 

PRAM is disconnected and I tried disconnecting the SCSI in case that was causing it not to boot. 

Any suggestions? The caps I can see so far looked good, and BMOW had it running about a year ago when he was testing his home built battery re-cell. 

 

[bigmessowires]

Doh! 

I disconnected the PRAM battery when I got it, as you've found. Before that, it wouldn't boot for me. 

The only thing that might be relevant is I always used the Duo in the Dock, or with my homebrew battery. I don't own a Duo charger so I never tried that. 

 

[mbaran]

I wonder if a duo will run with out any battery at all?

The charger definitely is putting out juice. I can always order 10 AAA cells and just keep it in there, if that's what it needs. I've got it down to bare board, it's clean, no cap goo. 

 

[mbaran]

it boots! Something in taking it apart has jogged it's ability to live!

edit, and it's dead again. 

 

[unity]

Maybe a cracked solder joint at charger input?

 

[mbaran]

It's one of the two  AT&T components on the main logic board (107-0134/152-0012) that is maybe faulty, but it's operating normally for now. One of them has an "electric" smell. The caps are all in that corner too.

Does anyone know if the capacitors on a Duo 250 are all on the logic board? I don't see any on the screen's inverter board, but I am getting very dark corners as it runs for a while. Powering it down and waiting seems to resolve it.

 

[TheWhiteFalcon]

If it's an active-matrix grayscale display, they all do that eventually. Flaw in the display itself.

 

[mbaran]

It is, and darn. Any particular component which can be replaced to de-accelerate that?

 

[TheWhiteFalcon]

The panel is the issue.

 

[mbaran]

got it.

Does the full size PowerBook have the same dual film membrane keyboard? My contacts are all corroded and typing is almost impossible on it. Strange design...

 

[TheWhiteFalcon]

The Duo's had a uniquely bad keyboard. I think you can do some work to them, but they're just not great from what I've heard.

 

[mbaran]

rock on. better find an ADB keyboard asap. the joys of old computers

actually, not even. My //c has an epic keyboard. 

 

[TheWhiteFalcon]

I didn't like the keyboard on my PB180 at first. I find it works better if you have the laptop up more towards you, and have your palms resting on the palm rests. You could try that.

 

[Elfen]

got it.

Does the full size PowerBook have the same dual film membrane keyboard? My contacts are all corroded and typing is almost impossible on it. Strange design...

Retrace the lines with a bit of conductive paint to fix it. I ruined a 230 board cleaning it with acetone, but was able to fix it with the conductive paint.

Look here for an example: http://www.radioshack.com/bare-conductive-pen/2760267.html

I've seen this design on many keyboards, including full sized PC Keyboards. It keeps the prices down in manufacture and very simple to make.

 

[mbaran]

That's actually a very good idea. I will buy a tube and touch up the troublesome keys. 

 

[Elfen]

Word of Caution:

There are two types, one that is made of carbon and needs a thick track, and another that is silver/grey that needs a thin trace.

Get the Sliver/grey one. And test it on a blank area of the plastic to see how it reacts to it. RadioShack keeps changing the formulations of this paint.