20Mb Kalok Harddisc from A420/1 - not spinning

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carcher
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20Mb Kalok Harddisc from A420/1 - not spinning

Post by carcher » Fri Jun 14, 2019 4:26 pm

I have been trying to get my A420/1 going again after many year in the roofspace.

When I power it on, it loads Risc OS 3.1 fine but the 20Mb Harddisc (Kalok) just makes head movement noises and does not seem to be spinning. I think the head is trying to access the disc, but it's not turning so it returns a disc error.

I removed the HD and took the HD disc controller PCB from the bottom of the drive to reveal the motor for spinning this disc. It rotates freely and smoothly by had, so it must be an electrical fault possibly with the motor drive circuit or motor. Has anyone come across this fault on the old ST506 drives?

Thanks
Chris

Kazzie
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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by Kazzie » Fri Jun 14, 2019 7:07 pm

The drive in my A420/1 is pernickety too, the point of death. I've managed to revive it a few times, but just to back up its contents to a CompactFlash card attatched to an IDE interface podule. It's now just acting as an unpowered paperweight in my case.

With my drive, I found that the spindle of the drive had seized. I suspect that it's due to a rubber washer or bearing decomposing over time into a sticky mess. (I have a film SLR camera that has the same problem on its shutter mechanism. If I leave the shutter uncocked, after a few weeks the film advance lever won't raise the shutter curtain all the way, and I have to partially disassemble the camera. If the camera's stored with the curtain cocked, then the force of the spring overcomes the sticky washer when I press the shutter.)

I found that depressing the drive's spindle (by pressing the small metal tab that covers it) a few times released it sufficiently that the motor could spin up properly. Then I just had to contend with bad sectors, until the spindle seized again. :roll:
BBC Model B 32k issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
Acorn System 1 home-made replica

carcher
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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by carcher » Fri Jun 14, 2019 8:17 pm

Thanks for the suggestion - I will give it a go!

TimoHartong
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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by TimoHartong » Fri Jun 14, 2019 8:32 pm

Or just try a could of times with power on and off. That helped for me . Harddrives cann't have it when they are not used on a regular base

philpem
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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by philpem » Fri Jun 14, 2019 10:40 pm

If the spindle hub rotates smoothly by hand but the drive won't spin up, either you've lost the 12V rail on the power supply (unlikely if everything else works fine) or the spindle motor driver's had it.
I haven't seen a Kalok in bloody years but they didn't have a great reputation even in the 80s and 90s... a working one would be somewhere between a miracle and a museum piece at this point.

Going forward, if you want to keep the ST506 interface, you could swap the Kalok for one of David Gesswein's MFM drive emulators://www.pdp8.net/mfm/mfm.shtml
Your other option would be an IDE podule and an IDE drive or Compactflash card.

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danielj
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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by danielj » Sat Jun 15, 2019 8:58 am

Also, the lube in the bearings of these can just gum up a bit with age. A drop of light mineral oil on the spindle bearing, turn it upside down so it enters by capillary action, leave it for 30 mins, wipe up any excess... That sometimes gets things going again!

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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by dangardner » Sat Jun 15, 2019 9:54 am

Given the age of the drive, the "freezer trick" might work for long enough to get data off but I just found https://www.pcworld.com/article/3035017 ... ymore.html which is worth knowing for more modern drives.

carcher
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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by carcher » Mon Sep 02, 2019 4:21 pm

Got some time at the weekend to try again with the Kalok. Removed the disc and took off the drive PCB. Spinning the drive by had - it seemed free enough. Re-assembled and powered on - it spins but after a few clicks and clunks from the head only ever returns with a disc error.
I suspect there is little else to be done there.

Now to try to get the SCSI card working....

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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by Kazzie » Mon Sep 02, 2019 8:08 pm

carcher wrote:
Mon Sep 02, 2019 4:21 pm
Got some time at the weekend to try again with the Kalok. Removed the disc and took off the drive PCB. Spinning the drive by had - it seemed free enough. Re-assembled and powered on - it spins but after a few clicks and clunks from the head only ever returns with a disc error.
I suspect there is little else to be done there.

Now to try to get the SCSI card working....
That sounds similar to my experience (though without removing the PCB). I found that while attempting to open files or folders on the hard drive invariably resulted in failure at a disc error, if I copied the files / folders off the hard drive (to my ZIDEFS CF card) then the OS would seek back to track zero and try again on errors, and eventually got most of the contents of the drive backed up.

This may or may not work for you, but you'll obviously want to get another drive working with your machine before you try it.
BBC Model B 32k issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
Acorn System 1 home-made replica

cmj6502
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Re: 20Mb Kalok Harddisc from A420/1 - not spinning

Post by cmj6502 » Tue Sep 03, 2019 10:37 am

I once got a ST506 drive going by spinning by hand to get it going at which point the motor could keep it going. It worked long enough to copy everything off.

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