Overcoming Stiction

[Cris]

Hi Guys

I am completely new (please excuse any stupid questions) to hard drive data recovery and have been researching the field with interest.

I was just wondering about proper (if any) methods of overcoming stiction without a cleanroom.

I noticed the Philips TDA5341 (Brushless DC motor and VCM drive circuit with speed control) chip has a "Friction Reduction" mode:

"...Pulling FREDENA HIGH activates the friction reduction mode of the TDA5341. In that mode, a clock signal fed via
pin TESTIN will cause the MOT outputs to sequentially switch-on and switch-off at the same frequency and, as a
result, generate an AC spindle torque high enough to overcome the head stiction.

Before start-up, the head stiction might be higher than normal due to condensation between the head(s) and the
disk(s). Normal spin-up is not possible when this friction torque is higher than the start-up torque of the spindle
motor. Spin-up is then only possible after friction has been reduced by breaking the head(s) free. Bringing a static
friction system into mechanical resonance is an effective method to break static friction head(s) free..."

1. I have not seen this "Friction Reduction" mode mentioned much, is this a relatively rare function for VCM/BLDC contollers?

2. How much extra torque capacity do spindle motors have, that hard drive circuits are not designed to use? For example if you had a case of stiction, could you remove the PCB and connect a custom motor controller to try and increase the torque, with something like this:

http://www.freescale.com/webapp/sps/sit ... IMCS08MP16

If this overcame the stiction, would it be considered as safe as any other method?

Thanks
Cris

[irs]

Hi Cris,
i think that "proper method" is opposite to "without clean bench or cleanroom".
If you force the motor to spin the heads will not have the air pulling them and they will not "fly" over the surface but probably scratch it.
The heads need the motor to reach right RPM before the unlatch.
hope this can help you
Bye
Luca

[Cris]

So out of interest, what is the proper cleanroom way to resolve stiction?

1. Slowly rotate spindle and park/ramp heads; or
2. Insert spacers between actuator arms, lifting heads from platters and then park/ramp heads; or
3. Introduce your own air flow into the system, creating air bearings and then starting drive; or
4. Something else.

I'm guessing number 2.

[thatdellguy]

5. Send to pro with cleanroom.


I'm guessing number 5.

[guru]

If you want to experiment: - http://bldc.wikidot.com/p-esc-motor

It is better to make your own ESC rather than mess around with the HDD PCB electronics.

Hi Guys

I am completely new (please excuse any stupid questions) to hard drive data recovery and have been researching the field with interest.

I was just wondering about proper (if any) methods of overcoming stiction without a cleanroom.

I noticed the Philips TDA5341 (Brushless DC motor and VCM drive circuit with speed control) chip has a "Friction Reduction" mode:

"...Pulling FREDENA HIGH activates the friction reduction mode of the TDA5341. In that mode, a clock signal fed via
pin TESTIN will cause the MOT outputs to sequentially switch-on and switch-off at the same frequency and, as a
result, generate an AC spindle torque high enough to overcome the head stiction.

Before start-up, the head stiction might be higher than normal due to condensation between the head(s) and the
disk(s). Normal spin-up is not possible when this friction torque is higher than the start-up torque of the spindle
motor. Spin-up is then only possible after friction has been reduced by breaking the head(s) free. Bringing a static
friction system into mechanical resonance is an effective method to break static friction head(s) free..."

1. I have not seen this "Friction Reduction" mode mentioned much, is this a relatively rare function for VCM/BLDC contollers?

2. How much extra torque capacity do spindle motors have, that hard drive circuits are not designed to use? For example if you had a case of stiction, could you remove the PCB and connect a custom motor controller to try and increase the torque, with something like this:

http://www.freescale.com/webapp/sps/sit ... IMCS08MP16

If this overcame the stiction, would it be considered as safe as any other method?

Thanks
Cris