Acoustic 'case modding'
The startup chime sounds not very convincing, as on most 1400s. Cause might be a kind of acoustic bypass preventing the speaker from producing some reasonable sound. Next time you dismantle the powerbook you might try to fix this speaker issue. It can be accomplished by either installing a compatible speaker of a better make fitting into the case or by sealing the speaker into it's frame in the PowerBook's housing. In each method be careful to aim at following points: the speaker membrane must not touch any other part or wire within range. The splice between frame and speaker must be sealed by the appropriate mounted adhesive rubber Apple used (you can remove this carefully and stick it again into place, if necessary), or by some kind of sealant like avrylic rubber for bath tubs.
I used this sealant to apply some damping glue into the gaps between the sheet metal and plastic housing of the PB, as well. This avoids resonant vibration of the sheet metal at several frequencies.