Info on HDD standard operation, repairs, anything ?

[Renate]

It had 6 of those huge vacuum reel to reel tape drives...

Vacuum column tape drives for the win!
Computers just used 1/2" tape.
The Ampex AVR-1 video recorder used 2" tape.

[MathWizard]

Ok I didn't realize there's only a few nm gap, so a dust particle would be like hitting a mountain.

I found some stuff on JTAG and HDD's, and found some similar BDCM controller/driver's like the Smooth L6230
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiOjtbm6YLuAhWbGVkFHbb6CCMQFjABegQIBRAC&url=https%3A%2F%2Fwww.st.com%2Fresource%2Fen%2Fdatasheet%2Fl6230.pdf&usg=AOvVaw2RDmsRGrptsCA-nD2zky9D

And the EPROM, but I don't know near enough to really do anything, I'd have to spend a week reading programing crash courses and still not get anywhere on that front.

I'm having a hard time finding where the power goes in the multi-layer PCB, so today I'll be going over those similar combo motor and inverter controllers or whatever they are.

http://bofh.nikhef.nl/events/OHM/video/d2-t1-13-20130801-2300-hard_disks_more_than_just_block_devices-sprite_tm.m4v

[fzabkar]

It had 6 of those huge vacuum reel to reel tape drives ...

I have a Cipher 900X in my garage.

[JohnnyMalaria]

Insightful video:



Step 1: Buy a laminar flow cabinet...

https://www.globalindustrial.com/p/medical-lab/laboratory-equipment/le-laboratory-fume-hoods/pcr-36-pcr-laminar-flow-cabinet-36w-x-35h-x-24d

[MathWizard]

1 thing thats way different between 2 HDD PCB I have here, is the resistance of the 3 phase output spindle motor. On the non-working Seagate PCB, there's 1.4143, 1.44xx, and 1.4xxx ohms between the 3 output pins, single ohms, not kilo

where as on my other seagate PCB, there's some 39k between any pair. So not the motor, the 3 pin PCB output to the BDCM spindile motor

[SilverSolder]

I found documentation for an older brushless motor driver chip - a chip that is simple enough that you could run it on a breadboard:  the Philips (NXP) TDA514x series.

Does not need a microprocessor to work...

Attached datasheet actually explains a lot about how to drive a HDD motor as well as documenting how this particular chip works.   

[MathWizard]

Well I checked another 2 seagate drives I have, 1 is like the working 1, and they have 40k or more between any pair of those 3 spindle motor pins. The non working 1 has the newest motor controller/voltage controller chip. But yeah I'll start trying to trace back and see why it seems a near short, they all have the same basic layout with 4 main inductors



Well they are shorted to GND, not just each other

Nope actually it's mosfets turning on/off, now it's reading like the other's, 40k or more.

I scratched a bunch of trace covering off, around the chip, and it doesn't seem like a dead short everywhere.

Dam I thought I found something useful

[helius]

The Bernoulli effect would be to draw the head and the platter closer together (fluid flow through a smaller cross-section causes pressure drop). The heads floating on the surface is the opposite effect, they have lift force because they are "wing" shaped.

[MK14]

The Bernoulli effect would be to draw the head and the platter closer together (fluid flow through a smaller cross-section causes pressure drop). The heads floating on the surface is the opposite effect, they have lift force because they are "wing" shaped.

Well, the following article, seems to agree with what I was saying:
https://www.welivesecurity.com/2019/02/18/smoke-damage-and-hard-drives/

Extract:

A hard disk drive’s read-write heads rely on the Bernoulli effect to float above the drive’s platters, and as air pressure decreases, the read/write heads begin to float closer to the platters.

[fant]

I have tried many times, but only once it worked, but better than nothing.

Freeze the failed HDD at -18 °C for some hours inside a plastic envelope, then very quickly power it and copy all the data in a  new disk.

Last hope.

Mandi

[Gyro]

I have tried many times, but only once it worked, but better than nothing.

Freeze the failed HDD at -18 °C for some hours inside a plastic envelope, then very quickly power it and copy all the data in a  new disk.

I'm not sure if I would risk actually powering the drive up at near -18'C. The oil in modern Fluid Dynamic Bearings might be too stiff to allow the spindle to spin up, at least in the required time. The motor driver might or might not tolerate that.

Irrc, the freezer method used to be a way of unsticking heads from the platter surface.  Modern drives usually park the heads off the platters on loading ramps rather than landing them on the platter surface.

Internal condensation is another potential issue.

[fant]

As I told you, once it worked.
If you have no other hope, is worth to try.

Mandi

[Mechatrommer]

If you have no other hope, is worth to try.

as been discussed/adviced countless number of times.. the better hope is plan ahead to make backup. there are cure for everything except death. if HDD is dead, there is no hope (at reasonable effort).

[Renate]

The point that I was trying to make previously was that to recover a 5 MB disk is about 600,000 times easier than recovering a 3 TB disk.

[fzabkar]

There are several drives which are designed to operate in sub-zero environments, such as inside a car.

https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/hgst/endurastar-j4k-series/data-sheet-endurastar-j4k320.pdf

Environmental (operating) - Ambient temperature -30° to 85° C
Environmental (non-operating) - Ambient temperature -40° to 95° C

[MathWizard]

I made a bit of progress, but I don't get the switching topology, I don't know them well enough anyways, but this doesn't match the datasheets of the controllers I looked at yet. But also this PCB has loads of via's that just disappear.

I got my Bus Pirate working over I2C on some MCU today, and I have now idea what to do at the command promt, besides turn on/off pwr and pullup resistors. So if my my HDD problem is in the MCU side, forget it, maybe next year I'll try again on that side.

I just wish it was a burnt out SMD part. I haven't bothered to pwr try to PWR anything on the PCB yet, I rather figure out the layout more 1st.

[SilverSolder]

It is highly likely to be a mechanical problem, not electronic.

Take it apart and turn it into a HDD clock... you know it makes sense!

[fzabkar]

This is an early "SMOOTH" combo spindle + VCM + power controller (L7250):

http://pdf.datasheetcatalog.com/datasheet/SGSThomsonMicroelectronics/mXyuswx.pdf

The chip houses the PWM control circuitry for the external DC-DC buck converters. You can identify these converters by the inductors located nearby.