Powerbook 100

[imactheknife]

Well, had a powerbook 100 that worked when I brought it home. Next power on, infamous black back lit screen. cleaned and recapped it, nothing, no change.. last one of these i buy.. two useless laptops.. anyone need a nice display or two??

 

[Cedsrepairs]

these are extremely difficult and frustrating to repair
I just finished my second one. It works - but this time I swear I am not touching a PB100 again.
The screen recap in particular is atrocious.
The mainboard uses that painful varnish that becomes sticky when cleaned with IPA
All the 1uF capacitors leak.
The harddisk has sticky heads, replacing it with an SD costs more than the price of the PB100 itself
The inverter never works "as new" even when recapped (the brightness range is wrong).

And none would buy any of those fully working units from me at any decent price. Heck - I wouldn't either.

It's a leap of faith.

 

[3lectr1cPPC]

The mainboard uses that painful varnish that becomes sticky when cleaned with IPA

So that’s why! I assumed it had just spread the flux I used all over the place instead of picking it up but I guess not. Wonder why that is. What specifically do you mean with the inverter board? Brightness or contrast?

I didn't find the actual recap that bad, maybe I'm used to difficult designs from fixing other PowerBooks though. Display recap is pretty easy if you get it down to just the LCD, removing all the frame and backlight layers from it.

 

[Cedsrepairs]

Nah there are a few vintage computers that share this awful varnish that makes a sticky goo when you try to clean it with IPA, the PB100 is one of them. You've got two solutions ; either you don't ever touch it with IPA, or you wipe it entirely by pouring a large quantity of IPA on top of the board, brush it until it's all gone and doesn't stick anymore... (but easier said than done)

The brightness : I've repaired three PB100 inverter boards and none of them seem to work properly after recap. I believe it's the potentiometer itself that's not working well, some active component, or maybe the tube itself (which by the way consumes a LOT of power, more than half the power a PB100 draws is the LCD backlight)

 

[3lectr1cPPC]

What behavior is the inverter board showing? Is the backlight too dim? My brightness dial seems to work properly but it does start a bit dim? Maybe not abnormally so but dimmer than my other PowerBooks. Not even close to unusable but dimmer. If anything, my contrast dial is the one with issues. I can get a great range of usable contrast and the screen looks really good, but at the lowest setting, I can still see the image clearly. On my other PowerBooks it will fully darken.

 

[Cedsrepairs]

Well it's like the first 1/10th of a turn is black, all off, then all of a sudden it's 90% bright, and the rest of the range (nearly all of it) is going from 90% bright to 100% bright. What's bizarre is that it's the second time I repair a screen that behaves exactly the same, so either I'm very unlucky, or I do something wrong.

 

[3lectr1cPPC]

May just be how these are. All my early PowerBooks behave like this.

 

[Cedsrepairs]

What is also possible is that they chose logarithmic potentiometers and not linear ones (for whatever reason).

 

[3lectr1cPPC]

What's the difference? Electrical component noob here.

 

[Cedsrepairs]

Well most of the potentiometers are linear nowadays

In the 80s as they were mostly used for (audio) volume, a lot of them were of the "log" type ;

Log and Lin Controls

Variable Resistors and Log and Lin Potentiometers. Linear and logarithmic or tapered types of track for different applications. How to make a linear potentiomer logarithmic.

learnabout-electronics.org

Basically the range is not linear ; if you do half a turn, you're not at 50% of the resistor value, you're at much more than that. (or much less depending which side you use)

So what could explain the weird behaviour of that brightness knob, if this is indeed stock, is that they decided to got for a "log" potentiometer... You could measure to confirm actually.

It could also be that the light tube is old, and doesn't light up like it used to... idk

 

[3lectr1cPPC]

Hmm. There’s gotta be a way to test that, would be interesting to see. The pots used on the 100 are also quite loose and easy to turn compared to the sliders on other models.

 

[CC_333]

Well most of the potentiometers are linear nowadays

In the 80s as they were mostly used for (audio) volume, a lot of them were of the "log" type

That makes some sense, and since Sony (which at the time was primarily into manufacturing A/V equipment, I think) manufactured the 100 for Apple under contact, it follows that the 100 might have some odd design decisions that are unlike virtually every other PB, such as, for example, the use of (possibly of the logarithmic, audio type*) rotary pots for brightness/contrast instead of the (presumably linear) sliders found on all other members of the 1xx family (save for the 190/5300, which used push buttons).

Until someone tests this hypothesis, it's hard to say if this is actually true or not.

c

 

[3lectr1cPPC]

Well, my PowerBook 145 and 170 also show the same behavior described.

 

[rollmastr]

Same here with a PB 160 and 165. I even recapped the inverter board of the 165 and noticed no change whatsoever.

 

[alexGS]

I’ve fixed three PB100s.
Two of them had a SMD resistor, 420k I think it was, that had gone open circuit - near the display cable connector on the logic board. This caused a no-backlight scenario.

The black-LCD scenario (i.e. all pixels black) is usually caused by the ~30V drive voltage not being present, in turn caused by the inductors being corroded near the trackball connector after the capacitor leakage in that area.

I’d love to say - send them my way but I live in New Zealand so it’s a long way to post.

I really like these machines; much better than all the other Powerbook 1xx machines (never get any broken hinge plastics or screw standoffs; actually nothing breaks), I love their rounded shape to the screen casing compared to the square shape of the others, they’re nice and slim, and I run mine off NiMH batteries.

I’m working on a Portable at the moment and it’s a nightmare in comparison…

 

[alexGS]

The harddisk has sticky heads, replacing it with an SD costs more than the price of the PB100 itself
The inverter never works "as new" even when recapped (the brightness range is wrong).

I’ve 3D-printed replacement bumpers for the hard drives - really just round spacers the arm rests against. I presume you have the Quantum GoDrive. I’ve replaced four of them now, two for my Compaq Contura Aeros as well I definitely wouldn’t fit an SD card device, it just wouldn’t have the same sound and feel!

I’d love to buy these Powerbook 100s with sticky hard drives off you, but you’d have to post them to New Zealand, sorry about that…

I remember these from the 90s and the backlight brightness is like the instrument panel dimmer in a 1970s FIAT. You have it on maximum, always. Turning it down will produce some intermediate setting and then OFF, that’s the limit of the adjustability

 

[Cedsrepairs]

Yes it's a matter of personal taste, the hobby allows to restore "in your own way" in many areas

I always replace hard disks because I consider they are timebombs, much more so than the rest of the electronics. They are also eating a lot of power which puts strain on the rest of the machine and external psu (even more so if you replace the battery like I did on one of my PB100)

However I always keep them so that they stay with their original machine. This can be reversed.

Good to know about the brightness setting ; it really looks like it does nothing !

 

[alexGS]

Yes it's a matter of personal taste, the hobby allows to restore "in your own way" in many areas

I always replace hard disks because I consider they are timebombs, much more so than the rest of the electronics. They are also eating a lot of power which puts strain on the rest of the machine and external psu (even more so if you replace the battery like I did on one of my PB100)

However I always keep them so that they stay with their original machine. This can be reversed.

Fair enough, you’re right - and I am glad to hear that you keep the hard drives - it would be a great shame to throw them away. Nothing should be thrown away

I think the biggest Powerbook 100 problem is with the LCDs. I’ve had two corrosion-affected displays and I currently have one with the ‘rot’ caused by trackball impact damage. As the rest of the machine is fine, I hope it can be combined with another some day.

 

[3lectr1cPPC]

Mine mostly works but the reset button is dead (maybe a bad trace somewhere) and it won’t boot if anything is plugged into the SCSI port, which is weird because it did in the beginning. Now it just acts like it isn’t recapped and immediately starts to the blue screen when plugged in, only if something is plugged to the SCSI port. But yes, I love the 100. Very robust plastics compared to other models, great design, great to use, etc.

 

[superjer2000]

I bought a PB100 a few weeks ago. The person I bought it from said it just had a blank screen but I didn’t power it up before recapping to verify. After recapping everything (except for a couple of caps on the inverter that aren’t the same as other PB1xx models) it fired right up. I installed a SCSI2SD and a 6MB module and it’s a great machine with an excellent form factor. I had always wanted one of these when they were being sold new. It’s amazing how much zippier the 16mhz processor is than the Classics 8mhz.

The downside is I am finding more software crashes on it than other systems. I think it’s due to a minimal check as to what processor is installed (and an 020+ Is assumed). For example StuffIt 5.5 requires an 020. I wasn’t aware of this and when running it on the PB100 it just crashes. StuffIt 4.5 mostly works. Virtual cd mounter quits with a bad f line instruction. But all other software (ClarisWorks, BlackKnight, MacTCP, etc) works great.