Geting a Disk Pack Working

discussion of games, software, hardware & emulators relating to the Acorn Atom
silvercreekvalley
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Geting a Disk Pack Working

Postby silvercreekvalley » Sat Jan 14, 2017 5:56 pm

Hi,

I've dug out my (ancient) Atom collection, and decided to try and get an Atom Disk pack working.

All seems to go OK, and I start off by typing

*DOS

then insert a disk and type

*CAT

I get a listing, but when I load a file eg

LOAD "BREAKOT"

Disk Error 18
Error 211

Which I think is bad sector read or sector not found.

I'm guessing that either a) the head is dirty and needs cleaning, or b) the stepper mechanism for the head movement is sticking?


Any help appreciated. I have some interesting custom Atoms - more on these later when I get this working :)

Ian

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danielj
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Re: Geting a Disk Pack Working

Postby danielj » Sat Jan 14, 2017 6:02 pm

Sector not found. Have a look at the floppy itself and see if it's gunky? Often the surface ends up mouldy and needs gentle cleaning off with IPA. Pop the lid, check the rails on the drive - they're probably a bit gunky. Clean and you could add a very little teflon grease... See if you can actuate the head back and forth by hand? Clean the head with something that won't leave lint in it and don't lever the top head (or pad) upwards too hard or far! :D

d.

silvercreekvalley
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Re: Geting a Disk Pack Working

Postby silvercreekvalley » Sat Jan 14, 2017 6:04 pm

Sounds like a plan - thanks :)

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danielj
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Re: Geting a Disk Pack Working

Postby danielj » Sat Jan 14, 2017 6:06 pm

If you push the head to the middle, then use the drive, it should pull it back to track 0 when you try and access a disc, so you'll be able to tell if the stepper's working.

d.

silvercreekvalley
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Re: Geting a Disk Pack Working

Postby silvercreekvalley » Sat Jan 14, 2017 9:14 pm

It does step back. Actually it will seek to the start of the file, and seems to read a bit in, and then stop with an error. I've tried several disks so its no the disk. Interestingly, the catalogue looks fine.

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MartinB
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Re: Geting a Disk Pack Working

Postby MartinB » Sat Jan 14, 2017 9:56 pm

Although I'm not familiar with the Atom, (I only use Beeb and Elk DFS), if the disc catalogue is ok but all file reads otherwise fail, that is often symptomatic of say a 40-track formatted disc in an 80-track drive or vice-versa. Is that a possibility in your case...?

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roland
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Re: Geting a Disk Pack Working

Postby roland » Sun Jan 15, 2017 12:04 pm

Can you format a disk without errors?
256K + 6502 Inside
MAN WOMAN :shock:

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Multiwizard
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Re: Geting a Disk Pack Working

Postby Multiwizard » Sun Jan 15, 2017 12:21 pm

Hi,

check also if there is any ram (2114) on the FDC card in your Disk Pack... 8)


Greetings, Wim... :-)

silvercreekvalley
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Re: Geting a Disk Pack Working

Postby silvercreekvalley » Sun Jan 15, 2017 5:13 pm

Thanks for all the replies.

The disks worked before, so I dont think its a 40/80 track issue - but good tip!

I cant seem to find my 'format' disk so havent tried that yet.

I've managed to get it to list the catalogue, and then move to the correct track when you LOAD, but it fails with an 0E now which I believe is a CRC error.

I'm thinking the head may be dirty, so I've removed the PCB from the drive, and now hunting around looking for something safe to clean the head with.

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roland
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Re: Geting a Disk Pack Working

Postby roland » Sun Jan 15, 2017 9:05 pm

Because you can read the catalog you can assume that the memory at #2000 - #2200 is fine. The Atom does not use the memory area #2200-#27FF for reading or writing regular files, only for random access files.

It can be a mechanical problem. Is there a stroboscope image on the fly wheel of the drive, like this:

2008-01-05-kaypro-clean-drive-flywheel.jpg


If yes you can check if the rotation speed is correct and constant. When you look at it in the light of a 50Hz light bulb, the 50Hz ring should be static. If it is not then you can check the belt or adjust the drive speed.

BTW you can find the disk errors on this page: http://www.acornatom.nl/sites/fpga/www. ... om_fdc.htm
256K + 6502 Inside
MAN WOMAN :shock:

silvercreekvalley
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Re: Geting a Disk Pack Working

Postby silvercreekvalley » Sun Jan 22, 2017 5:05 pm

Thought I'd post a progress report.

So I cleaned the head on the drive and this seemed to improve things a bit. The basic problem is that the stepper motor is a bit stiff, and doesn't seem keen to move at times. If I move the plastic rail assembly slightly, it moves and will load a file OK.

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danielj
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Re: Geting a Disk Pack Working

Postby danielj » Sun Jan 22, 2017 5:35 pm

Have you cleaned and lubricated the rails (I'd use a light coating of teflon bike grease)? If you've done that but it's still the motor being stiff, then you're into the realms of replacing the stepper motor, which is also the realms of "drive out of alignment"... At that stage it's possibly worth thinking about trying to source another full height floppy (alternatively you can run two half height drives in there!)

You can't really strip and lubricate a stepper motor unfortunately, I think the whole thing's a sealed unit...

d.


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