Toshiba MK1234 head stiction causes and consequences

[shaun]

Hi all,

today I found a spare hour to continue practicing
I still got the MK1234 with sticking heads I wanted to learn on, and in the mean time an identical working version arrived.
So I swapped the head stacks between

Disk A: stopped working from one second to the other, the notebook has not been touched when it happened. I found the heads sticking somewhere in the middle of the platters. I was able to release them and did not see any obvious damages to the heads under the microscope, but the disk does not work properly - it takes ten of seconds to become DRDY and then reads 20-50kByte/s

and

Disk B: a perfectly working MK1234.

Now the big surprise: Disk B works with the head stack from A, a bit noise, but flawless.
But Disk A still takes much too long to DRDY and re-seeks to track 0 every few seconds.

I noticed that the spindle of Disk A has more friction than that of drive B, it instantly stops when turned manually while A's spindle keeps turning several seconds.

How do these drives fail except from being dropped? I imagine spontaneous spindle seizure which causes the heads to drop onto the platters and stick there. Would the bearings be permanently damaged and probably cause the problems I'm having now?
Recently some of you wrote that these drives aren't too picky about platter alignment, so my next attempt would be to swap the platters to the base of the working drive and have a look at the surfaces - maybe one of them has been damaged by the sticking heads. The upper surface looks good, I looked at the place the head stuck to and did not see anything special (from the experience of a learner...)

[BlackST]

Cause of the seizure : poorly designed motor AND not designed for continuous use (how to make people understand that they cannot open their laptop and use it as a Emule client 24/7 ?) .
Consequences : the heads "fly" on the platter thanks to a thin air interface between the slider and the platter surface. When the spinning speed is insufficient to make the head "fly" it lands on the surface... and for simple surface tension and/or suction effect, the head gets "stuck" on the platter.

Beside head assemblies and platters, ADAPTIVES play an important role.

The drive that reads slowly may have :
- Rotational problems (doesn't reach target speed = servo locking problems)
- G-list overflow and/or SMART thresholds triggered.

Why the head from A work on B ? It's not unlike. The fact it doesn't work 100% is because adaptives make the drive fine-tuned for HIS heads (physical and electrical) but the different headsets match sufficiently.

[drc]

Perhaps when the stiction originally occurred it jarred the platters ever so slightly out of alignment.

[jono-ats]

Resistance in rotation is proof that the bearing is bad on drive A. Bad bearings cause slow reads and read errors in Toshiba drives.

The older Toshibas weren't too picky about alignment, but I believe the 1234 series is. Be careful or you risk the data.

[HDD Spaz]

Disk A has bad bearing but good heads. I believe the fluid dynamic bearing has gone bad, possibly conjealed. Very common with Toshiba hard drives. Disk is not able to get up to speed so slow sector read rate. There are techniques to get the disk working again without physical work but a platter swap is probably the safest option (for a pro).

[BlackST]

Unless you are able to make it spin decently for the time needed for imaging.

[HDD Spaz]

Unless you are able to make it spin decently for the time needed for imaging.

I know what you speak of, I must admit this is the route I would take but either way is safe for a pro, afterall they are pros.

If they are not pros then it possible that processor gets melted or platters get dropped

Moral of the story, safe techniques for pros not for others.

[shaun]

@hdd spaz: what techniques are you referring to?
I don't think the repeated "for a pro" is necessary here. I wrote that I am practicing on this disk, something every pro would probably have done somewhen, decades ago
I'm in electronics development for more than ten years, but new in hard disk mechanics.

@all: what's your opinion and experience in platter swapping and alignment for this particular disk?

[HDD Spaz]

Search the forum for Toshiba fluid/bearing, I'm sure theres loads of posts on the subject. In the rare event that I actually need to swap platter on a toshiba, I have never had a failed recovery. SD tools will be good enough to swap platters on these disks so alignment wont be a problem. Or you could develop your own technique and tools.

If you consider the fluid in the bearing is like an oil, when an engine gets hot, the oil thins enabling smooth running of the engine. Theres your answer.

[shaun]

Thanks, I searched the forum and found what you were referring to. I'll try this tomorrow (I hope)