Need advice on how to recover 5.25" floppy

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brightcaster
Posts: 188
Joined: Fri Nov 08, 2013 10:48 pm

Re: Need advice on how to recover 5.25" floppy

Post by brightcaster » Sun Jan 20, 2019 12:20 pm

Yes, resurecting deleted files is possible on the images created with kryoflux software. You can use the common dos tools for that purpose.

You only need a separate power suply for the drive itself. The Kryoflux board is powerd via the usb cable.

You may also download the software from kryoflux.com and play with it without having the hardware connected. This may give you an idea about how everything works. Also the manual included in the zip-file will be usefull...

David

harlus
Posts: 16
Joined: Wed Jan 16, 2019 7:06 pm

Re: Need advice on how to recover 5.25" floppy

Post by harlus » Mon Jan 21, 2019 9:09 am

brightcaster wrote:
Sun Jan 20, 2019 12:20 pm
You only need a separate power suply for the drive itself. The Kryoflux board is powerd via the usb cable.
I have a PSU from an old desktop pc that has molex connectors, i think it should be ok to supply the drive, right?




However, i unmounted the drive from the case, and I took some pictures.

This is another label i found on the drive:

Image

It seems it's a FD-55B


This is the drive:

Image


And I suppose these (circled in red) are the heads:

Image

At first sight they don't seem dirty. But i have no experience in these things, so my question is: usually the dust on the heads is something "macroscipic" or it is an almost-invisible layer? Do you think it is worth it to clean them in this case? (i know the picture is not much clear but it's the best i can do, it's not easy to take a good picture of them)


One last thing, this is the floppy cable:

Image

Do you think it's ok to use it or it's better to buy a new cable?

brightcaster
Posts: 188
Joined: Fri Nov 08, 2013 10:48 pm

Re: Need advice on how to recover 5.25" floppy

Post by brightcaster » Mon Jan 21, 2019 9:57 am

Okay, this drive looks right beeing a 360k double sided drive. After such a long time resting in a shelf I would give it a cleaning with a Q-Tip and isopropanol or similar. The cable looks worth a try...

David

SomeGuy
Posts: 217
Joined: Wed Feb 18, 2015 8:18 pm

Re: Need advice on how to recover 5.25" floppy

Post by SomeGuy » Tue Jan 22, 2019 4:03 pm

Yes, head residue can be transparent or small enough that it is hardly visible.

Although I have had the pleasure of cleaning drives where the entire head assembly was buried in brown oxide gunk.

harlus
Posts: 16
Joined: Wed Jan 16, 2019 7:06 pm

Re: Need advice on how to recover 5.25" floppy

Post by harlus » Fri Jan 25, 2019 5:47 pm

Thanks for your answers, i'll try to clean the heads before starting the work.

I decided to buy a kryoflux even if it's not strictly necessary, because it may be useful in case of demaged disks, and moreover it has good documentation and support forum.

While i'm waiting for my kryoflux, i've some other questions for you:
- is there some jumper or similar things on the drive that i need to set? (for the kryoflux board itself it's all explained in the manual)
- if a disk gets completely read with no errors, does it make sense to save it also in .stream format? Or it's only a waste of space?
- what format should i choose for the image file in my case? does "CBM DOS" stands for "IBM DOS"?
- (this is not a "pratical" question, i'm just curious) how does kryoflux knows that a track has been read correctly? Is there some checksum, or parity bits or other similar tecniques?

brightcaster
Posts: 188
Joined: Fri Nov 08, 2013 10:48 pm

Re: Need advice on how to recover 5.25" floppy

Post by brightcaster » Fri Jan 25, 2019 7:37 pm

If the drive has been in use with a usual pc I would leave all the jumpers in place.

If the disks are not copy-protected and you only want to get some personal files of them it's not nessesary to save the stream data.

CBM stands for "Commodore Business Machines" and IBM for "International Business Machines". So theese are two different companies using two different formats. What you need for MS-DOS disks is "MFM sector image".

The kryoflux software does calculate the checksums of a given format. If they are correct you get a good read and valid data. If you only save the stream data you can never be shure about the consistany. Therefore it is better to use a so called format guided dump where you save the stream data plus the decoded data of a given format. If you get a checksum-error on a certain track or sector than, this part is either defectiv or copy protected (which should only happen with comercially duplicated software).

David

harlus
Posts: 16
Joined: Wed Jan 16, 2019 7:06 pm

Re: Need advice on how to recover 5.25" floppy

Post by harlus » Tue Jan 29, 2019 8:51 am

The big part of my disks are home-written, so they're not copy protected.
But I also have a few disks that were attached to some magazines, I don't know if they have some kind of copy protection.

So, if I understand well, if a disks gets read without errors, it's 100% sure it's not copy protected. If there are some errors, it can be defectiv or copy protected.

Like I said some posts ago, it would be nice if I can recover deleted files from the disks.
To do so, do I only need the image files or do I need also the stream files?

One last question: we spoke about cleaning the heads (i cleaned them some days ago), but can it be useful also to clean the floppy itself? are there some techniques to do so? or it's better not to touch them to avoid demage?

SomeGuy
Posts: 217
Joined: Wed Feb 18, 2015 8:18 pm

Re: Need advice on how to recover 5.25" floppy

Post by SomeGuy » Wed Jan 30, 2019 7:22 pm

So, if I understand well, if a disks gets read without errors, it's 100% sure it's not copy protected. If there are some errors, it can be defective or copy protected.
Not necessarily. There are some clever copy protection methods that can make a disk look completely normal. That said, most of the time, yes you will see one or more bad or mis-formed sectors.

One trick that I have found handy is to use the HxC software tool (there are probably other tools too) to graphically plot a stream dump. It will show bit decoding errors as red spots. Most of the time, at least with IBM PC disks, that indicates real disk damage. A "bad" sector that has no red spots in it typically indicates it was intentionally written that way and is probably copy protection.

To simply recover deleted files, you would typically take a decoded image file, mount it in an emulator, and then run DOS tools to attempt undeletion. If it were me, I'd probably still keep a stream dump for reference, but the stream file is not directly needed for this purpose. If it turns out there was actually disk or sector damage then the stream file can be useful.

I have found cleaning disks usually increases the chances of getting a successful read and decreases the chance of damaging the disks while reading. I'm not aware of any "standard" method to clean disks. There does exist the possibly of damaging disks during a cleaning process, but it is a trade-off.

Always visually inspect the floppy magnetic surface before putting it in to a drive. Visible residue or damage is a red flag that bad things might happen. However, junk in the disk may not always be visible, or may be in the jacket lining instead.

In a nutshell:

- You can clean visible spots with a q-tip and water. Only use isopropyl alcohol for tough stuff, as that can also remove magnetic oxide coating on low-quality or already damaged disks. This may not remove junk stuck in the jacket lining.

- You can "rinse" 5.25 inch disk with hot/warm water by running water in around the hub. The trick is getting them dry without having the jacket stick to the surface.

- Data recovery professionals cut the jackets open, bake the cookies to prevent shedding, and place the cookies in known good jackets. Obviously you don't want to do that with collectible original software titles.

If you are lucky you might not have to do anything. Start with some disks in the batch that are not important, and adapt your methods bases on those results.

harlus
Posts: 16
Joined: Wed Jan 16, 2019 7:06 pm

Re: Need advice on how to recover 5.25" floppy

Post by harlus » Thu Jan 31, 2019 9:38 am

Thank you, it's all more clear now.

So, what happens if a disk is copy protected? Will the software in the image work properly (assuming that there are not "real" bad/demaged sectors)?

Also, what happens if a disk is demaged? Will the files from the other parts of the disk be accessible in the image?

SomeGuy
Posts: 217
Joined: Wed Feb 18, 2015 8:18 pm

Re: Need advice on how to recover 5.25" floppy

Post by SomeGuy » Thu Jan 31, 2019 1:54 pm

So, what happens if a disk is copy protected? Will the software in the image work properly (assuming that there are not "real" bad/demaged sectors)?
It depends on the protection scheme and where you try to run it. Most emulators don't support copy protection. Those that do still don't know about every single protection method out there. Even if you make a physical copy, some protection schemes are still enough to trip up the Kryoflux.
Also, what happens if a disk is demaged? Will the files from the other parts of the disk be accessible in the image?
Completely depends on where the damage is. If it is in the FAT or directory area, then nothing may be accessible. If it is in one file then just that file may not be accessible. If it is in unused space, then you are lucky and everything else should work.

It is also important to note HOW the damage is handled. If a sector is completely omitted or an extra sector is inserted in an image file, then it can throw off programs like Winimage, making every file that follows the bad area look bad. If an "empty" sector is filled in instead, then things stay in place.

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