I can't quite believe it myself, but I managed to repair my Lombard Powerbook, which has given me little pleasure and lots of grief over its lifetime. I resoldered the power connector on the sound card and after assembling the laptop back together it indeed booted without a battery. This happened only a mere week after I managed to tweak my Laserjet 4 printer so it didn't jam on ever paper. There I cleaned and lubricated the rollers and slightly changed the paper flow, all to apparent good effect.
This is in marked contrast to my usual repair efforts, which leave the devices even deader than they were before.