Need help recover 8 bad sectors on a 800KB HFS Mac floppy from the 90's

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Alex
Posts: 40
Joined: Wed May 26, 2021 11:44 pm

Need help recover 8 bad sectors on a 800KB HFS Mac floppy from the 90's

Post by Alex »

Hello everyone,

I'm fiddling with my last Macintosh Plus 800k floppy from High School. It's full of bad sectors and trying to do a good dump with 10 different 3.5" drives. I managed to get a good read of most of the bad sector on a drive or another but for the remaining 8 bad sectors nothing worked. I cleaned the disk with 99% isopropyl alcohol and tried another round of dumps but again no luck.

I was wondering if someone can look at the disk (again this is an HFS format):
https://tinyurl.com/7kc7s4tx
This is quite big (578 MB compressed) as it contains most of my attempts. Maybe someone can recover the last 8 tracks from all my dumps?

In the archive, the "000-402-Mix" folder contain a mix of the good reads from many drives while the other folders are a specific dump from a single drive. Folders ending with "L" are dumps with "Density Line Low" checked while folders ending with "H" are with "Density Line Low" not checked. The folders ending with "-final" are dumps made after cleaning the floppy.

For me this is a precious floppy as it's from high school and it's in those labs where I did those (mostly boring assignments) that I decided to become a software engineer.

Thanks for your time!
SomeGuy
Posts: 348
Joined: Wed Feb 18, 2015 8:18 pm

Re: Need help recover 8 bad sectors on a 800KB HFS Mac floppy from the 90's

Post by SomeGuy »

Araaaag! Damaged Macintosh disks! Just saying, I've been down this road a number of times, and it is always a headache.

PC style floppy drives are not designed to read these, so the signal must be in good strong condition for a Kryoflux to read them.

First of all, what specific brand/models of drives did you use? I have found Teac and Toshiba brand drives are the best and most others are useless.

Also, most 3.5" drives IGNORE the density line setting and use the physical notch instead. I only know of one model from an IBM machine (I forget the exact model number off hand, but I mentioned it in a previous thread) that honers the density line. Typically, overriding density does not make things "better", but it does make things "different".

Have you been able to try it in a genuine Macintosh drive? (Most of the time, Mac drives are actually worse at reading damaged disks, but in a few cases they succeed.)

You did the right thing by saving all flux dump attempts. Different software tools may have better luck. Which software tools did you use? Just the Kryoflux software?

Also do the disks look at all physically damaged? Typically, I don't recommend alcohol. At this point, I would not recommend additional cleaning, as run through drives this many time already should have left it as "clean" as possible.
brightcaster
Posts: 477
Joined: Fri Nov 08, 2013 10:48 pm

Re: Need help recover 8 bad sectors on a 800KB HFS Mac floppy from the 90's

Post by brightcaster »

On some drives, the HD switch can be manipulated easily with a crochet hook while the floppy is inserted in the drive...

BTW: Is the floppy physically HD or DD (with or without a HD hole)? I ask this because HD floppies written with DD drives sometimes look similiar in the HxC disk analyzer...

David
Alex
Posts: 40
Joined: Wed May 26, 2021 11:44 pm

Re: Need help recover 8 bad sectors on a 800KB HFS Mac floppy from the 90's

Post by Alex »

These are the drives brand/model I used (I have multiples of some model):

Code: Select all

Brand		Model		Tracks	Date		Condition
Alps		DF354H090F	84	Feb 2005	Used
NEC		FD1231H		82	Oct 2005	New
Panasonic	JU-257A827P	84			Used
Samsung		SFD-321B	84			Used
Sony		MPF520-D	82	1996		Used <--- Sets the density based on the Density Line Low/High setting instead of the density notch on the floppy
Sony		MPF920		84	May 2005	New
TEAC		FD-235HF	82	2008		New
Answering all your questions :) :
  • Yeah you are right, overriding density did not make things better but I tried everything :)
  • I don't have a genuine Mac that I tested the disk with.
  • I just used the Kryoflux software. I didn't know that the raw files were usable with something else (I'm quite new at dumping).
  • I read that 99% isopropyl alcohol was safe for disks and used it with a vinyl disc cleaning cloth (since I doubted this - that's why I did this step after doing everything else possible).
  • The disk surface seems OK and was always stored in a "good" environment.
  • The disk is a regular 1 hole 720KB 3.5" floppy but looking at it it's labelled "KAO MF2DD Double Sided 1 MB Capacity".
ZrX
Posts: 663
Joined: Tue Dec 06, 2011 9:09 pm

Re: Need help recover 8 bad sectors on a 800KB HFS Mac floppy from the 90's

Post by ZrX »

Checked all the dumps and *Sony2* seem to have gotten the best results.

For what I see in the raw data, cleaning the disk shouldn't make much of a difference. It could be a drive alignment issue...

You could try dumping the disk using that Sony drive with the drive open, and while it's past track 47 try pushing the head assembly either towards the inner or the outer tracks with your finger (not too hard that it skips tracks and NOT by pressing on the top of the head), you can often push on the spring part at the rear of the head carriage. If that results in less errors it'd suggest that the original Macintosh drive was slightly out of alignment.

If the outcome is still the same it's possible those modern drives are pushing up the signal gain too fast as the bits at the inner tracks are much wider apart than on standard PC floppies.
Alex
Posts: 40
Joined: Wed May 26, 2021 11:44 pm

Re: Need help recover 8 bad sectors on a 800KB HFS Mac floppy from the 90's

Post by Alex »

I'm not too fond of manipulating the head while the read is in progress... Can't this damage the floppy and/or the drive? I ordered 2 other 3.5" drives: a Toshiba and a Mitsubishi (two brands that I didn't have). Maybe I will be more lucky with those drives (I doubt it)? I'll keep you guys updated...
SomeGuy
Posts: 348
Joined: Wed Feb 18, 2015 8:18 pm

Re: Need help recover 8 bad sectors on a 800KB HFS Mac floppy from the 90's

Post by SomeGuy »

Pushing the head down too much, yes that can potentially damage a floppy. But in your case the suggestion is not to push the head down but rather forward or back - so you would actually push/pull on a part of the head assembly other than the head itself. That should not damage a disk.

Some of those tracks show quite a bit of random noise. Continue to keep as many flux dumps as you can, and keep trying different drives. These dumps looks like many of the damaged Macintosh disks I have run in to - the sectors in a track may intermittently become borderline readable, so the more dumps you have of the problem tracks, the more likely you may be able to piece a track with multiple bad sectors back together as only one sector may become readable at a time. Unfortunatly the Kryoflux, by its nature, operates on whole tracks rather than individual sectors, which makes this process a pain.
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