endless beep after hibernate in AC-mode

Archived from groups: comp.sys.laptops (More info?)

Here is an old TP 560Z that shows a strange behaviour - or is it just normal?

Whenever the machine hibernates when connected to the power supply and system
beeps enabled the hibernation procedure finishes with a never ending beep. In
DC-mode however, the final beep sounds like you expect it.
It doesn't matter what OS is used or how hibernation is triggered. The beep
stops as soon as I disconnect the power supply; reconnecting will it *not* bring
back. If I disable the system beep (again - no matter how) the machine keeps
silent.

In *any* case hibernation has successfully finished.
So, it's not a big thing - it's just annoying.
But I'm not sure whether there are more serious troubles behind.
Is this a warning from the power control?
Shouldn't I hibernate in AC-mode (but how to specifically disable it for AC-mode
on a 560Z)?
Do I miss something else?

With the exception of the BIOS (I got a little bit anxious in the last years to
unnecessary flashings) everything should be up-to-date. The CMOS battery *was*
low but I replaced it (and performed an "Initialize" ).

Stephan