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Powerbook 100 display issue

techknight

Well-known member
I've seen this once and fixed it by replacing the full display, maybe its the cable or something?

In this case it was not. like I said it was a failure in the logic board, it was not providing one of the required voltages for the display.
 

techknight

Well-known member
Right here:

1639620928393.png

one of the two 150uH inductors, the pin gets eaten away, and it fails. prevents that voltage from being generated.
 

Trash80toHP_Mini

NIGHT STALKER
What are the specific component designations?

Hazarding a guess here, but figured everyone else who's not up to snuff on this stuff would like to know as well. Are the inductors good to go with a trace repair or should they be replaced along with the caps?

On the dead pixel front: I just bought another 100 for backup parts from a member. Very happy with it, knew it had trackball damage, but the rubber on the lid appears to be intact. The spacing of lid to base is perfectly even front to back, so the rough handling hypothesis still stands for some 100s I think.

Will the panels with that damage ever work again or are they gone for good? The screen was what I wanted to use for my test setup, go figure.
 
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3lectr1cPPC

Well-known member
The screen should still work with a recap, it will just not display anything on the damaged area. Sure, it will always have that defect but it could be a lot worse.
 

Cedsrepairs

Well-known member
I'm flattered to be quoted as a source of info for PB100 repairs :)

Indeed my own screen suffers the same problem, and it's trackball impact ( due to the long grey rubber stripes turning into goo, so less thick, and the ball that's never supposed to touch the screen now touches it)

This especially happens during shipping (so if you buy a PB100 that looks neat, ask the seller to remove the trackball !)
However, all plastics in PBx series are VERY brittle due to age; so it's likely removing the trackball will... break the pins of the trackball ring around it (been there). Choose your evil !

Yeah --- retro computing is full of frustration I think of selling all my collection twice a month. And then go on. :)
 

captjon320

Active member
I will have to get pics with the details, but here is the root cause:

You are missing the twist voltage that drives the panel. its a 20 to 30v supply and its generated by the converter on the logic board. This voltage goes missing and that causes the black screen when the computer seemingly boots. Why? this boost converter sits right next to big ass leaker tank farms that need replaced and the electrolyte eats away the nearby components stopping the DC-DC boost converter from running.

I’m working on one of these and after the recap, ultrasonic wash, bake and dry; I now get a backlit screen and nothing else. I would be gracious if you could point me in the correct direction to fix the voltage. I have included some pics of the area I believe you are talking about, but do not know where to go next.

EDIT: sorry, just found your picture.

Are these the two that likely need replacement?
 

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techknight

Well-known member
No, they dont need replaced. they need removed and checked. to make sure they are still good and traces underneath are fine.

All three of them btw
 

captjon320

Active member
No, they dont need replaced. they need removed and checked. to make sure they are still good and traces underneath are fine.

All three of them btw

Update: removed all three and the traces look good on the board. The inductor from L3 (right in between all four caps) has the plastic molding broken off underneath, which holds the pins steady on the bottom. This may have been from my removing, but it’ll need to be replaced. I have included some pictures.

Once I get away from capacitors, I'm way out of my league. From your previous picture I would guess this is one of the 150uH inductors? The ones I took off are not labeled.
 

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captjon320

Active member
Update: I checked the continuity of all three inductors and they are good, so I don't know where to go from here. Traces look good as well, I have posted some pictures from yesterday. If there is another area I should focus on trouble shooting, I'm open to ideas.
 

PotoMac

Active member
I'm doing this exact repair & my L3 broke a leg as well while I was desoldering it. Appears to be pretty common.

What should I replace it with? I'm shopping for 150uH's but what Maximum DC Current do I need? Mouser has up to 50 A.
 

Cedsrepairs

Well-known member
I just got a new PB100 today, of course it does not start and has leaky caps.

So i'll recap a PB100 once again.:)

I've been lookin for one since a long time, as I've got a perfectly working one (recapped, bluescsi, etc) but it had red dead pixels due to trackball impact

This new PB100 I bought has a perfect screen, and is less yellowed...

I'll probably update my previous topic, it's likely I'll chose the replacement caps (even) more carefully.
 

imactheknife

Well-known member
I just got a new PB100 today, of course it does not start and has leaky caps.

So i'll recap a PB100 once again.:)

I've been lookin for one since a long time, as I've got a perfectly working one (recapped, bluescsi, etc) but it had red dead pixels due to trackball impact

This new PB100 I bought has a perfect screen, and is less yellowed...

I'll probably update my previous topic, it's likely I'll chose the replacement caps (even) more carefully.
Any update:)
 

Cedsrepairs

Well-known member
Do you believe me if I tell you that since posting this I have bought no less than two other vintage computers all needing repair

Is there like an AA for vintage enthusiasts to share their problems buying useless junk ? :)

Joke apart the parts are in, this is my next next project.
 
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