Ah. Indeed. No Portable yet, so the process is moot for the moment.
The GOOD NEWS, is that the display is working again. After disassembling the display housing, I tightened all the connections and the display pops on again perfectly. It could have been a loose connection that pulled apart when flexing the screen. I believe this unit had a modem originally (as the control panel is still on the hard drive) and someone likely loosened the connections when salvaging it. Probably had more RAM too, given the System and other software on it. HOWEVER, I'm going to let the thing sit for several days just to ensure the caps just hadn't finally reached sufficient charge, in which case they will discharge and it won't work again.
Having now SEEN the inside of the display housing, you may well be correct that the Portable's display will NOT fit, even with substantial modifications. I'll just have to wait and see one. I'll post some pictures and measurements for other Portable owners to review and post their own internals. Perhaps we can nip this whole thing in the bud without ever lifting a knife! Also, the Portable appears to use a ribbon cable to connect its LCD works, something that would have to be adapted to the 100's more traditional headers and wires.
Added 5/5/08 (Happy Cino De Mayo)
Tom, I was thinking the best way to go about upgrading the 100 to an Active Matrix display. I've decided one way to go about it is to use the 170 which already uses the 9.8" diagonal 1-bit active matrix display. I should be able to swap the 100 logicboard into it and use all the same connectors. The rear ports are likely not going to line up, but thankfully any changes required will be hidden behind the rear port door/cover. The battery may not fit, but the lead acid battery is virtually useless anyway. I think that is likely the better way to proceed with this experiment.
AND before anyone jumps down my throat, the reason I want to do this is to run a 68000 laptop under System 6, but with the crisp display I am used too with LCDs and CRTs. Also, the 170 case design is technically the very first PowerBook design after the Portable anyway. The 100 was delayed due to Sony's miniaturization and its case was actually improved upon based on what they learned with the 140/70. Also, the PowerBook uses an inverted SnowWhite scheme, raised 2mm x 10mm ridges rather than indentations. Sony simply shrunk the 140 design to fit the smaller 100 case thereby altering the proportion, so while the later PBs echo some of the changes the 100 brought about, it is the only one with that unique altered style. In that sense the 140/70 are the most authentic original examples of the first PowerBook. Though one could argue the 100 with it's 9" diagonal screen is closest to the original compact CRT.
LASTLY, A NEW consideration: I am going to try the HDI-20 Floppy drive cable with the HD20 to see if my theory that the HD20 which Apple says will work on the Portable will also work on a PowerBook 100. At the moment the header is a mini version of the standard floppy drive connector which means I will have to adapt it to mate with the HD20 header. But first I am going to make sure the pinouts are 1-to-1 as the adapter may be more involved than just mating connectors.
Here's the relevant signal info:
PIN 5-10 DB-19/HDI-20
5 -12/NC
6 +5/+5
7 +12/+5
8 +12/+5
9 NC/+5
10 PWM/NC
Given that the HD20 is self-powered, I suspect that none of these voltages are critical. Pin 10 is likely ignored by the HD20 as well since it neither used the PWM signal nor the later Superdrive voltage. The only question is pin-9 ... if the PowerBook 100 generates +5v on a pin the HD20 doesn't expect, will it affect the HD20 or will it ignore it completely? Also, if the PowerBook 100 is generating no signal on pin 5, will the absence of any voltage affect the HD20?
A helpful link: http://www.fantasticthings.co.uk/Hacks/duo_floppy/superdrive_to_duo.htm