| SX64-Drive: reading ok, writing fails sometimes [message #210418] |
Mon, 04 November 2013 18:49  |
Rudolf Harras
Messages: 129
Registered: March 2012
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Hi!
Recently I noticed some strange misbehaviour of the inbuilt floppy drive
of my Commodore SX64.
I didn't notice any problem for a long time. All the games worked fine,
even I didn't notice any problem with saving highscores.
The problems started when I tried to copy a disk image from my 1541U to
a disk in the internal 1541. This failed, the directory was always
corrupted (wrong number of free block, font turning to white). After
some while i noticed that the same disks worked fine with other drives.
So, there seems to be an error when writing on the disk, no mather which
programme I use for copying things. The problems seem to start when
files are bigger and/or when writing above some sector. As long as the
disk is empty and files are not big there doesn't seem to be any problem.
Would be great if someone could give me a hint what this could be or
where to start searching.
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| Re: SX64-Drive: reading ok, writing fails sometimes [message #210419 is a reply to message #210418] |
Mon, 04 November 2013 23:38  |
Ray Carlsen
Messages: 75
Registered: March 2012
Karma: 0
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Member |
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> Recently I noticed some strange misbehaviour of the inbuilt floppy
> drive of my Commodore SX64. I didn't notice any problem for a long
> time. All the games worked fine, even I didn't notice any problem
> with saving highscores.
<snip>
> So, there seems to be an error when writing on the disk, no mather
> which programme I use for copying things. The problems seem to start
> when files are bigger and/or when writing above some sector. As long
> as the disk is empty and files are not big there doesn't seem to be
> any problem.
Hi Rudolf,
A very common problem with the ALPS mechanism in the SX drive is
sticky rails, a purely mechanical problem that masquerades as
misalignment. The ALPS mechanism seems prone to that failure more than
the Newtronics (twist door latch) type. Because of old sticky lube, the
sliders that ride on those two metal rods under the head assembly don't
follow the tracks accurately enough, especially at the ends of travel
where large programs store information.
When I get an SX on the bench, before I do anything else, I clean
the drive rails with solvent, slide the head assembly back and forth and
swab the rails repeatedly until no more residue is seen and the assembly
moves easily. Don't forget to clean the spring-loaded block just to the
right that holds tension on that metal band. The block should also be
free to move but is usually stuck because the grease used at the factory
turned to "honey" and locks it in place. After cleaning, the drive can
be run "dry" as re-lubing will usually attract dust and get sticky again
eventually. One drop of lube in the spindle clamper will keep it working
but if it starts to stick or make noise, it may have to be taken apart
and cleaned before it's re-lubed. Of course all this requires the drive
be removed from the SX. Swapping the mechanism with a Newtronics is not
possible because its door latch sticks out too far to allow the keyboard
to be put back in place on the front panel.
Ray
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| Re: SX64-Drive: reading ok, writing fails sometimes [message #210421 is a reply to message #210418] |
Tue, 05 November 2013 12:46 |
<address_is
Messages: 19
Registered: January 2013
Karma: 0
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Junior Member |
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Rudolf Harras <rudi007@temporaryforwarding.com> wrote:
> The problems seem to start when
> files are bigger and/or when writing above some sector. As long as the
> disk is empty and files are not big there doesn't seem to be any problem.
When the disk is freshly formatted it saves around track #18. When there
are more files, it needs to move the head further away from the centre. The
same if the files are long. Check if you can properly format the disk with
this drive (and use it in another drive) and if the head carrier moves
freely, without being "sticky". If needed clean the rails and lubricate
with proper "clockwork" type of lubricant. HTH.
--
SD!
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| Re: SX64-Drive: reading ok, writing fails sometimes [message #210423 is a reply to message #210421] |
Tue, 05 November 2013 13:39 |
Rudolf Harras
Messages: 129
Registered: March 2012
Karma: 0
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Senior Member |
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Am 05.11.2013 18:46, schrieb address_is@invalid.invalid:
> When the disk is freshly formatted it saves around track #18. When there
> are more files, it needs to move the head further away from the centre. The
> same if the files are long. Check if you can properly format the disk with
> this drive (and use it in another drive) and if the head carrier moves
> freely, without being "sticky". If needed clean the rails and lubricate
> with proper "clockwork" type of lubricant. HTH.
No, formatting without error is not possible.
But if this happens because of this, why would the head read from all
disks without any problem?
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| Re: SX64-Drive: reading ok, writing fails sometimes [message #210451 is a reply to message #210423] |
Tue, 12 November 2013 15:07 |
Spiro Trikaliotis
Messages: 380
Registered: December 2011
Karma: 0
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Senior Member |
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On 2013-11-05, Rudolf Harras <rudi007@temporaryforwarding.com> wrote:
> Am 05.11.2013 18:46, schrieb address_is@invalid.invalid:
>
>> When the disk is freshly formatted it saves around track #18. When there
>> are more files, it needs to move the head further away from the centre. The
>> same if the files are long. Check if you can properly format the disk with
>> this drive (and use it in another drive) and if the head carrier moves
>> freely, without being "sticky". If needed clean the rails and lubricate
>> with proper "clockwork" type of lubricant. HTH.
>
> No, formatting without error is not possible.
>
> But if this happens because of this, why would the head read from all
> disks without any problem?
For reading, the drive retries if there are problems.
Wild guess: This might help in reading disks even with the above
problem.
If the rail is not going properly, then the drive might end on another
track than it expected. The read routines read in a sector header, find
the track number (which is wrong) and correct their view of the current
track.
IIRC, the floppy would retry to step the disk head.
I am not completely sure about that last part. However, if this is true,
this might help in reading disks even with the above problem.
Regards
Spiro
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| Re: SX64-Drive: reading ok, writing fails sometimes [message #210455 is a reply to message #210423] |
Sat, 16 November 2013 13:26 |
<address_is
Messages: 19
Registered: January 2013
Karma: 0
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Junior Member |
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Rudolf Harras <rudi007@temporaryforwarding.com> wrote:
> Am 05.11.2013 18:46, schrieb address_is@invalid.invalid:
>
>> When the disk is freshly formatted it saves around track #18. When there
>> are more files, it needs to move the head further away from the centre. The
>> same if the files are long. Check if you can properly format the disk with
>> this drive (and use it in another drive) and if the head carrier moves
>> freely, without being "sticky". If needed clean the rails and lubricate
>> with proper "clockwork" type of lubricant. HTH.
>
> No, formatting without error is not possible.
>
> But if this happens because of this, why would the head read from all
> disks without any problem?
Good question. Reading is a somewhat different process from the 1541 point
of view but I am not sure if different enough to make it the way you
experience. Anyway, it was not a diagnosis. Just a hypothesis, a thing
worth checking. If not in order to solve the problem, then at least to
eliminate one potential cause of it. Please update us on the results.
--
SD!
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