Modern desktop spinning rust drives usually have a small capacitor backup that lets them park the heads if a power failure happens but .. no idea if laptop drives have this ability so its possible the blackout caused the bad sector but if it was a head crash I would expect more than just one bad sector so im leaning to it being a coincidence.

My (possibly dated and/or erroneous) understanding of mechanical HDD head retraction is that, upon power loss, the kinetic energy of the still spinning platters is typically used to safely retract heads through the use of a purposefully designed mechanical coupling .

AFAICR, a drawback of that type of system is that if power is cut while the platters are not spinning at nominal velocity (either because the drive was just powered on or because several brief power on/off events occurred in a short enough timeframe), there may not be enough kinetic energy in the spinning platters to properly retract the heads .

Please correct me if I am completely wrong or if this is no longer true for more recent designs .

EDIT : @Trash Panda Do you know when that kind of capacitor-backed mechanism might have become commonplace on consumer drives ?

darry wrote on 2022-01-13, 18:42:

EDIT : @Trash Panda Do you know when that kind of capacitor-backed mechanism might have become commonplace on consumer drives ?

I know that my first "notebook", a 386SX20 40MB HD already had a "parking function". They advertised that (around 1992?)

darry wrote on 2022-01-13, 18:42:

My (possibly dated and/or erroneous) understanding of mechanical HDD head retraction is that, upon power loss, the kinetic energ […]
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My (possibly dated and/or erroneous) understanding of mechanical HDD head retraction is that, upon power loss, the kinetic energy of the still spinning platters is typically used to safely retract heads through the use of a purposefully designed mechanical coupling .

AFAICR, a drawback of that type of system is that if power is cut while the platters are not spinning at nominal velocity (either because the drive was just powered on or because several brief power on/off events occurred in a short enough timeframe), there may not be enough kinetic energy in the spinning platters to properly retract the heads .

Please correct me if I am completely wrong or if this is no longer true for more recent designs .

EDIT : @Trash Panda Do you know when that kind of capacitor-backed mechanism might have become commonplace on consumer drives ?

Seems I wasn't totally right about the capacitor reserve, some modern drives use a method where the heads dont land on the drive platters when parking and instead are removed from the platter area by a magnetic parking platform, others use a method you suggest, I remember reading about the capacitor backup that allows the heads to finish moving away from the platters during a power outage but I cant remember where, it might be part of the system that removes the heads from the platters via the parking platform and I have simply confused it for its own system when its part of a bigger one.

https://www.datarecoverytools.co.uk/data-reco … ing-of-rw-head/

This site lists the methods being used currently.

Power loss CAN cause bad sectors (it's stated into most HD datasheets).
They are soft bad sector, that means they are not actually bad sectors
but data and checksum doesn't match. They could be easily fixed by Simply
rewriting them.

Run a scan with HDAT2 (https://www.hdat2.com/), if it's a soft bad sector
it will be fixed with no problem, but chkdsk will always report it as bad
sector; it fixes only logical file system issues (and if you have serious
physical error on the drive will just add some trouble...)

BTW what's the model of the hard disk?
Can you post a SMART log?

verysaving wrote on 2022-01-14, 01:28:

Run a scan with HDAT2 (https://www.hdat2.com/)

Looks useful, thanks for the link

Three suggestions:
- My old Fujitsu laptop had a depleted CR2032 battery. This caused boot problems (black screen, HDD detection errors, but never complained about CMOS values). Maybe you should check that.
- If you replace CMOS battery and the computer still have boot problems, you should run it without main battery. Your battery may be putting extra workload on your PSU, and may cause it to fail.
- Check the SMART parameters of your disk. Usually, by the time chkdsk/SanDisk catch a bad block, the hard disk has silently reallocated many others. If the reallocated count and the pending reallocation is 0, probably it was a glitch (and HDAT2 will cure it). If not... well your HDD is not trustworthy.

If I had a blackout it could lead to a head crash ;p
Think your situation is a coincidence..

Good news! Now i can force the computer to generate more bad sectors: When trying to boot while the flat battery is charging, i get the Windows splash-screen, a min later it stops and i see the bluescreen = not enaugh voltage or Watt. When booting with full or removed battery, everything works.

Strange: chckdsk now reports 28 bad sectors kb (512 bytes per sector) (1 old, 27 today) on vol f:, but SMART (CrystalDisk, SIW & Defraggler) seems not detect anything. Also, the used area in Defraggler was red before, today it looks blue = clean (???).

However, i will have to replace the battery before changing the HD visit ebay for a new 30 Euros-notebook.

edit: mixed up things (as usual).

Zup wrote on 2022-01-14, 06:27:

... depleted CR2032 battery. This caused boot problems...

Thanks, the CMOS battery is fresh. I shall run the computer without main battery until i get replacement ...