Dealing with DISCKIT3 "data error" and "missing address mark" errors

[Jonathan]

I got a Gotek for Christmas and have been merrily backing up my old 3" discs. 

Most discs have worked fine. 

A sizeable minority showed a data error on DISCKIT3 but blowing on the surface of the disc got rid of the error after retries.

A few still give errors:
* "data error" - "Within system track" (a few discs).
* "missing address mark" - "Within system track" (one disc).
* data error with a specified filename affected (one disc).
* data error with a "fortunately this does not matter" message (one or two discs).

Are there recommended ways of cleaning the disc surface? On one disc I can see with my old eyes that the surface is not uniformly shiny.

If the disc itself can't be cleaned, what's the best way to recover what data is left?

Thanks in advance.

[Devlin]

A bit of ipa on a q-tip and *GENTLE* cleaning as you carefully rotate the centre spindle is usually enough to handle minor errors

This is what I did when I was imaging amiga disks a while back - your mileage may vary, given the CPC discs are a lot older.

[Jonathan]

If the disc itself can't be cleaned, what's the best way to recover what data is left?

I'd be interested in answers to this part of the question too. I think that for all of the discs the "CAT" command works fine and programs run. If the disc errors are all in the system tracks, does that mean the data files are all OK? If it does mean that then I would just copy the files to a blank disc image on the Gotek. Thanks.

[arnoldemu]

A bit of ipa on a q-tip and *GENTLE* cleaning as you carefully rotate the centre spindle is usually enough to handle minor errors

This is what I did when I was imaging amiga disks a while back - your mileage may vary, given the CPC discs are a lot older.

I've done this with 5.25" discs and I've also used cold tap water but once I've dumped the disc I've thrown it out. It also takes time to clean the entire surface on both sides and ensure it's dry. I've not tried with a 3" disc.

[arnoldemu]

If the disc itself can't be cleaned, what's the best way to recover what data is left?

I'd be interested in answers to this part of the question too. I think that for all of the discs the "CAT" command works fine and programs run. If the disc errors are all in the system tracks, does that mean the data files are all OK? If it does mean that then I would just copy the files to a blank disc image on the Gotek. Thanks.

Yes if the catalogue can be read without errors and the remaining data.

A few choices with discs that have errors:
* The errors may be part of a protection so consider if the disc is protected or not and these errors are expected.
* clean the disc surface using ipa and/or clean water, ensure it's dry and then do an entire dump of the disc and hope it is ok.
* do a single copy/dump of the entire disc and then recover files from it one by one to another disc - ok if it's not protected
* sometimes during a dump if you retry many times it can read the data successfully on one of the tries.
* do multiple dumps and try a piece the bits together (e.g. some tracks from one disc, some from another).

Be aware if you are getting read errors there is the potential that the disc drive heads could be getting dirty and they might need cleaning and that the disc itself is failing so it may not be worth keeping but perhaps copying to another disc that is error free.

As I said, I've been through a load of 5.25" discs which were stored in a damp/dirty garage for many years, and after cleaning i managed to recover a lot but it took a lot of patience and I had to clean the drive heads a few times.

[Jonathan]

Thanks for the detailed answers. I won't ask about cleaning the drive heads until I come to that bridge... but what program(s) can copy a disc despite the errors then combine the working parts of several images? This sounds promising as DISCKIT3 fails on the first error but sometimes it's a different track/sector.