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#11
A transient into a motherboard may have corrupted CMOS settings. Battery voltage would be irrelevant. A PSU normally would have averted (blocked) that transient. Problem is an adjacent protector that compromised (bypassed) that PSU. Adjacent (power strip) protectors have a long history of connecting a transient directly into the motherboard; bypassing what is superior protection.
Anyone can see that. For example, take a meter. Measure conductivity from that protector's third prong (on its AC plug) to many IC pins and other motherboard parts. That is the direct connect that a transient would have used to only corrupt CMOS settings.
That transient is averted at the breaker box - a 'whole house' solution. If that computer needed protection, then all appliances (motorized and electronic) also needed that protection. Even near zero joule plug-in protectors need that protection.
It was a tiny transient. Would have only corrupted some CMOS settings. Next time, the transient may be significant - do hardware damage.
Do not waste money on plug-in boxes. Those do not claim to protect from typically destructive surges (as specification numbers make obvious). Apparently a 'whole house' protection system does not exist (that costs about $1 per protected appliance - it is that inexpensive). That 'whole house' solution necessary to even protect tiny joules in a plug-in protector.
BTW holding down a front panel button does not drain capacitors. Those capacitors have bleeder resistors (typically 100K ohms) that drain charges in seconds. Those bleeder resistors were standard for protecting human life - even back when electronics used vacuum tubes. All capacitors are automatically discharged in seconds.