Questions about hard drive innards

[jimmyj68]

Mom in-law's computer visited a local computer shop after I ran out of ways to troubleshoot a post/start windows opening screen/reboot - post etc. problem. Guy says the Maxtor 40gig hard drive from year 2000 has bitten the dust bunnies. I gave her a spare 80 gig WD I had on hand and she was off to the races until as a xmas present we rebuilt her computer and took her out of the world of pentium III into a P4 630 and a Biostar I915G-M7 mobo.

Any who --- I took the opportunity to disassemble the hard drive since it went out of warranty in 2003. Here's what I found and and the questions raised.

They used four platters for 40 gig, 10 per platter I assume. But the "wipers" were on both the top and bottom of the platter. Does that mean they were taking 5 gig from each side?

I encountered the most powerful magnets I'd seen since the days of yore and aircraft radar power tubes - magnetrons (I know, they are everywhere now in microwave ovens), the only thing is those old tubes had huge magnets attached. In this hard drive were two magnets, about an inch long and one half inch wide and an eigth of an inch thick. They bracketed the end of the wiper carriage over a tightly wound semi -triangular
flattened (?) tightly wound coil.

1. Obviously any movement of the coil between the poles of these super magnets would produce a current in the coils - but how were the movements of the wipers across the platters controlled?

2. Near the wiper axis and control magnets is a small plastic coffin like container filled with what looks like very tiny black BB's. What are they for?

3. The control board was surprisingly, electrically connnected to the wipers, platters and motor by pressure connectors not unlike those in the p4 socket 775. Flat connection points on the reverse side of the board made contact with tiny pins on the drive substructure.

4. The motor, about the size of three stacked fifty cent pieces manages to spin the four platters at 7200 rpm. Why can't motors that small be used in case fans and cpu heatsink fans?

Well, that's tonight's adventure ------

 

[Jeff7]

1.) Not quite that obvious, apparently.
Current is passed through the coils, which produces an electromagnetic field. This is used to move the "wipers" which are the read/write heads. Each head floats a tiny distance above the surface, and at the end of it is a tiny coil of wire. This is the head itself that detects magnetic fields on the drive platters, and it also is capable of changing those magnetic fields to write data.

2.) This sounds like a container of dessicant, but I'm not sure.

3.) Yup

4.) It probably doesn't have a lot of torque, nor does it need it. The platters spin with little wind resistance. A fan needs a beefier motor to effectively fight wind resistance imposed by the moving blades. I imagine that a hard drive motor would spin a fan fairly slowly, overheating in the process.

5.) Helpful information

 

[Frodolives]

Some older Maxtors could be temporarily "rejuvenated" by removing those rubbery pads infused with thin wires that created contact with the spin motor and heads. They got dried out and compressed, and you could soak them in an alcohol solution overnight before replacing them to put some life back in it.

At least enough for data recovery, hehe.

 

[jimmyj68]

Thanks for the "How Things Work" lead. I'm imagining that a linear motor like that in this Hard Drive moves that coil at one heck of a pace if the magnetic strength of the stators is any indication. It also has to stop it when it is moving at this tremendous clip. Because of the location of the pivot point the heads do not move at the same pace as the coil but as indicated in the article - they move fast. What i'm curious to know is how the start and stop points are signalled to the coil so as to find a particular information byte. This has got to be unimaginably precise as well as powerful enough to stop the fast moving coil at the precise desired point

A long time ago, in my early Air Force career I was priveleged to work with the guidance system on the BOMARC ground to air interceptor missile. It used analog "computerization". A fairly simple but quite sophisticated methodology for the times, that just matched voltage levels with mechanically driven stepping switches and other such mechanisms. This was in the early 60's and was also my first introduction to transistors which figured in the analog computation acting as simple switches where the on/off state of the transistor in conjunction with the mechanically driven voltage matching enabled the missile to be guided by rf energy to a given point in the sky where a built in search radar would then locate the target aircraft and take over "flight" control of the missile.

The bomarc was literally a pilotless airplane with full wings and vertical and horizontal stabilators. A liquid fuel rocket got it of its launching stand and up to the speed needed for two ramjet engines to kick in. It went high, and it went fast. And it went where it was told. The advent of ballistic missiles and the demise of the manned bomber put and end to the BOMARC. I am thankful we never had to use one in defense.

That was approaching 50 years ago. I can't imagine what the Air Force has in guidance technology today. And they can fit an entire guidance package in a unit small enough to attach to an iron dumb bomb and make it smart enough to go down a chimney. The guidance and control package in the bomarc took up the entire nose of the missile (about 5 feet in diameter).