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Lorne
January 23rd, 2010, 05:26 PM
I just received a 5161 Expansion Unit which has a Seagate ST-412 hard drive in it.
It's got this sort of arm type thing (like a latch) on the side of it, connected to the motor.
In the first photo's position it's not where it looks like it should be.

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In the second photo, I've moved it around to where it sort of looks like it should be, locking in place in something.

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Does anyone have any idea what this is?
I haven't seen this on any other Segate drives.
Thanks,
Lorne

ruthlessperson
January 23rd, 2010, 05:30 PM
That's that stepper motor that controls the heads. Don't move it around without the drive spinning it's dragging the heads across the platters. I am pretty sure the track 0 or home swtich.

Jorg
January 24th, 2010, 12:16 AM
Yes, if you search the forums, you will find some threads on it- mainly about how to use it to relocate track 0 (when bad).
I hope it the drive works and you do not need those posts, because it is pretty much last resort.
Aha: http://www.vintage-computer.com/vcforum/showthread.php?2114-What-to-do-with-a-defect-ST-412-drive&highlight=st-412

nige the hippy
January 24th, 2010, 02:17 AM
Ouch! yes, don't move it again! I've had "apprentices" come into my work area, pick up a perfectly happy drive, and wiggle the damper/lock wheel/track zero flag, on the end of the stepper. Bye bye drive.
AFAIK you should shut down systems, with stepper operated hard drives, that are likely to be moved, with a drive-parking program running, which will put the heads over the "landing zone" - a data free area. Voice coil drives do this by default, and I'm not sure, but I seem to remember some drives that zipped the stepper in as soon as the power started to dip.

Dwight Elvey
January 24th, 2010, 06:16 AM
Hi
As others mentioned, this is not to be moved without the
drive spindle running.
It is quite likely that you've already done damage.
The position it was in is the typical park position
The position you rotated it to is the track0 where
the sensor it interupted by the level arm.
Dwight

Lorne
January 24th, 2010, 08:15 AM
OK, so it sounds like I've probably screwed it.
You'd think they would have put that lever in a more inaccessible place, so idiots like me don't start messing with it.

Always trying to look on the bright side of a bad situation, the drive may have been toast anyway.
It was used "as a print server until the mid 90's until a power outage knocked it out".
So, sometime in the mid 90's the thing went off, they've moved it around their office, it was shipped to me via FedEx, all the while with the heads not parked because it never ran again after the power outage.
I'll see what happens when I power it up, after I get the other bits working.
If worst comes to worst, I'll try the stuff mentioned in the other thread that Jorg posted about.

Thanks for the info. (at least I'll have learned from my mistake)

Chuck(G)
January 24th, 2010, 08:38 AM
Seagate used to put ominous red-on-yellow warning labels not to touch the thingy on all of their early drives, including the 14" and 8" winchesters. Is your ST412 missing one?

Regardless, the 412 is a pretty tough drive. Give it a shot; low-level format it and see what you've got.

channelmaniac
January 24th, 2010, 01:00 PM
If you've hosed track 0 then MS-DOS will not work. I've had luck using DR-DOS on drives with bad track 0 though. ;)

Lorne
January 24th, 2010, 02:28 PM
Seagate used to put ominous red-on-yellow warning labels not to touch the thingy on all of their early drives, including the 14" and 8" winchesters. Is your ST412 missing one?


Just a Fragile and a Handle with Care.
Absolutely nothing about don't touch this bloody lever or you'll mess up the drive !

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Chuck(G)
January 24th, 2010, 02:59 PM
Maybe they figured it was like a "Do not touch - Wet Paint!" sign.

MikeS
January 24th, 2010, 07:23 PM
Well, moving the heads of a stationary HD is certainly not recommended, but it didn't necessarily cause any damage that wasn't there before; I've certainly done it with no ill effects. As Chuck suggests, try it out and if it's really dead then it probably already was.

FWIW most drives I've seen with an external track 0 sensor had a clear protective cover over it.

Dwight Elvey
January 24th, 2010, 08:00 PM
Just a Fragile and a Handle with Care.
Absolutely nothing about don't touch this bloody lever or you'll mess up the drive !

3012

You can damage the disk by rotating the spindle the wrong way
as well. I know this because I got one from a friend and he
wanted to show me that it wasn't froze up.
When I took it appart to see what had happened. There
was a nice radial groove cut from that back of the head
in the surface.
Dwight

MikeS
January 24th, 2010, 08:05 PM
You can damage the disk by rotating the spindle the wrong way
as well. I know this because I got one from a friend and he
wanted to show me that it wasn't froze up.
When I took it appart to see what had happened. There
was a nice radial groove cut from that back of the head
in the surface.
DwightAh, now *that* I would definitely not recommend ;-)

Chuck(G)
January 24th, 2010, 09:19 PM
FWIW most drives I've seen with an external track 0 sensor had a clear protective cover over it.

But not the ST506 and ST412. The 506 has a nice green-and-silver warning label not to touch the "interrupter". That's what the "lever" is, by the way. Somewhere around the positioner stepper there will be an opto sensor that the end of the "lever" passes near.

8" and 14" Seagates have a clear plastic widget over the end of the positioner, but I think it's some sort of dashpot.

MikeS
January 24th, 2010, 10:35 PM
But not the ST506 and ST412. The 506 has a nice green-and-silver warning label not to touch the "interrupter". That's what the "lever" is, by the way. Somewhere around the positioner stepper there will be an opto sensor that the end of the "lever" passes near.

8" and 14" Seagates have a clear plastic widget over the end of the positioner, but I think it's some sort of dashpot.It's funny, I originally called it an "interrupter" and then changed it to track 0 sensor because interrupter sounded odd; the things we remember...

The drives I'm thinking of are the 3.5" Miniscribes, don't think anyone else still had external interrupters by then. Used to get a kick out of watching them twitch during a seek test, even glued a little white pointer to some of them so you could clearly see where the head was.

nige the hippy
January 25th, 2010, 11:16 AM
8" and 14" Seagates have a clear plastic widget over the end of the positioner, but I think it's some sort of dashpot.

That's the damper.
I was quite intrigued the first time I saw one, I didn't understand it. It's a metal disc inside a clear plastic case. the disc is connected to the shaft, the case is free to rotate, but is coupled to the disc by a liberal coating of grease.

Chuck(G)
January 25th, 2010, 01:03 PM
That's the damper.
I was quite intrigued the first time I saw one, I didn't understand it. It's a metal disc inside a clear plastic case. the disc is connected to the shaft, the case is free to rotate, but is coupled to the disc by a liberal coating of grease.


A dashpot is a mechanical device, a damper which resists motion via viscous friction.

The curious thing is that the housing doesn't seem to be tethered to anything either. It must offer exactly the right amount of damping to keep the settling time reasonable.

tezza
January 26th, 2010, 01:09 AM
I just need to look at vintage gear and it seems to stop working.

I'm not even going to come within a barge pole's distance drives like these!:D

Tez

Lorne
February 7th, 2010, 10:38 AM
The Seagate ST-412 is apparently toast.
I did a low level format on it, but then got an "Error Reading Fixed Disk" message when I tried to FDISK it.
I won't be touching one of those levers again.