So, the PowerBook
3400c / 180 MHz is now fully functional(?) again — and you’re now working with your now problematic
3400c / 200?
"Mine" however, is still blocked at this "grey" screen and deeply dependent on an ADB mouse being plugged or not. Even if the cursor is unusable. - Tazintosh
So the focus is now on the
3400c / 200, which will not fully boot unless you’ve an ADB mouse attached… and if you disconnect that mouse during extensions loading (or other processes) it stops?
AND without the mouse connected, you cannot get past the grey screen during any attempted boots?
Sounds to me like the mouse attempts to complete a missing or faulty necessary connection that your keyboard (and / or trackpad) are not providing… and possibly due to poorly or improperly connected (or even damaged) ribbon cable(s). This is why I suggested disconnecting the keyboard and possibly even the trackpad, and substituting them with an ADB keyboard (with mouse attached).
You say that you’ve not had any issues with the keyboard, yet --it will not completely boot without the ADB mouse connected.
Now, you may not wish to go to the trouble of removing the
3400c / 200’s keyboard and / or trackpad again, or even closely inspect all ribbon cable(s) and their connections… but you might try attaching the ADB keyboard from your
Power Macintosh 550/275 — just to see if things might change? Yet without disconnection of the keyboard & trackpad, you have not changed the possible conditions of either of those possibly interfering with the ADB mouse’s full function.
You had no problems with this machine (
3400c / 200) until you opened it up for modification, disconnecting and reconnecting cables.
And while the ADB mouse (previously) does not provide a working cursor, this might also be a symptom of the questionable keyboard or trackpad connections… interfering with the mouse’s full & complete operation.
In essence, substituting an ADB keyboard and mouse as a possible workaround — to see if keyboard or trackpad might be the source of your problem(s). Granted, the ADB keyboard & mouse substitution might not change things but might be worth the attempt.
AND, I only assume that the ADB mouse currently works fine with your 3400c / 180 MHz?
Sorry, no “magic bullet” or simple solution here. I’ve run out of ideas.
Best of luck to you.