HDD Power consumption

[bigal.nz]

Hi Folks,

I decided to experiment the other day with connecting a desktop Seagate drive to a regulated, twin output, DC power supply - really just for curiosity's sake.

I noticed on the outside of the drive it had the current rating for both the 12v and 5v lines - the rating for both was about 0.8amps. Accordingly I set the over current protection on the power supply to 0.8 amps.

When I powered the drive up I got a repeated, mechanical clicking sound (this is on a known good drive). So I upped the current limiter to 2 amps and now the drive powered fine. It seems when it was limited to 0.85 amps it couldnt get passed the inital surge required when the drive first is powered on and spins up - after the inital surge it stayed within paramters (0.8 amps).

Is this normal?

What else can a regulated power supply be used for in terms of diagnostics?

Any replies or PM's gratefully received.

-Al

[dobrevjetser]

Yes, its normal.
The current neccessary to make the platters start to spin is much greater than the current needed to keep them spinning once they rotate.
See it as a car that has to accellerate; then your fuel consumption is sky high. Once you've reached the desired speed, fuel consumption drops to a much lower level.

I've only used current consumption so far for to diagnose a bad pcb.

Best regards,

Dobre

[bigal.nz]

Thanks for that - it makes perfect sense.

Coincidentially I have got a disk here that a friend claims was dropped. Its not detected in Ubunutu or Windows. If I connect power it used about .5a on 5v rails, but when I try connecting to USB bridge power drops to about 0.1 amps.

Do that give any clues as to where the fault might lie?

Cheers

-Al