Why are 3" floppies so expensive?

[eto]

and should sell some ...

Please make sure not to sell to cosmoretroshop. He will just list them again, but for more money. 

[harzretro]

and should sell some ...

Please make sure not to sell to cosmoretroshop. He will just list them again, but for more money.

That is one of my problems, that is why i prefere to swap stuff instead of sell things

[GUNHED]

Probably they got stored at an improbable place.

Hmm, what kind of places? Who's the enemy, humidity?

Yes, I guess that's one important point. And also drastic change of factors (humidity, temperature...) during the cycle of day. 
I don't even want to mention magnetic fields (power lines ...) else this thread will get derailed.

[GUNHED]

Hmmm, i've hundreds of discs here, but i don't need them all ..... but they are used and never tested ones ...
And i don't know what is on this discs ....

Offtopic: You can use FutureOS to look at them very quick...

- Put disc 
- Klick at the drive Icon 
- look at directory
- change to next disc...

But now for every disc you just need to press D for DIRectoy and you can swap the disc immediately, because the drive motor will not run any longer. 

Sorry for getting off-topic, hope this hint is of general interest. 

[eto]

I did a format and verify with the spare disks that I got over the last 4 years.

About 2/3 have bad sectors. Brand did not matter but the source I got them from did matter a lot.

• the discs from some sellers were either mostly good and the bad disks only had a few  bad sectors
• from other sellers almost all of them were bad and most of them with lots of bad sectors

I could revive some sectors by using a magnet and formatting the disc again. I will try again with a stronger magnet as I couldn't find it yesterday and used smaller ones.

One interesting aspect: Even some discs that I used in the past which worked actually had bad sectors. You might think your disk ist fine - until you format it again.

The tool I used is MultiMark. It is quite fast to format disks, then verifies them and marks bad sectors so the disk can be used without the risk of writing to the bad sectors. For disks with only a few bad sectory this seems to be quite reliable. If the disk has many bad sectors I would not do that as some sectors seem to change with every format/verify.



MultiMark also has a directory feature. So you can select the drive once and then just hit D to output the directory of the current disk.

[darkhalf]

I have a few Maxell disks which are still shrink-wrapped and in 100% mint condition

Same. I found someone in our local retro group selling a bunch of sealed and some near-new. There may not be a guarantee of 100% good sectors on sealed ones since they still mould. However pricewise on ebay you could make something from it. I would rather keep mine, given how difficult it is to find them here in Australia.

What I did find is that the near new ones had a few with bad sectors. Looking through the Greaseweazel facebook page some people have had success with 80% IPA (not the beer) removing mould. That may not always be the cause

Some of the no-name brand discs (another batch) were that bad I've experimented with transplanting 3.5" (cut/pate) into a 3" disc. It kind of works, but getting perfect circumference is difficult to last the least.

[eto]

Some of the no-name brand discs (another batch) were that bad I've experimented with transplanting 3.5" (cut/pate) into a 3" disc. It kind of works, but getting perfect circumference is difficult to last the least.

How do you open them and put everything back again? I tried with one and I can't get it back together.

some people have had success with 80% IPA (not the beer) removing mould

Indeed I just could fully revive one disk that had dozens of bad sectors before. However on other disks there was little or no improvement.

What also worked quite well is using a strong magnet to demagnetize the disk and then format again. At least for disks with only a few bad sectors about 1/3 no longer had bad sectors. And a lot of the rest has improved with less bad sectors. 

[darkhalf]

How do you open them and put everything back again? I tried with one and I can't get it back together.

I've found it very difficult. You have to use a knife or similar to break the plastic apart and then super glue to put it together. I did about two and found it took a lot of time. Getting the slider in place with the spring loading and holding it place took many tries

However on other disks there was little or no improvement.   
What also worked quite well is using a strong magnet to demagnetize the disk and then format again

Agreed with cleaning no improvement. I've also tried the magnets too. So far I've not had much success reviving what I have so far, but others on the greaseweazle page with other disks have, so will need to try some others. I got a batch for free from market place recently which have some sides okay and other sides bad sectors

I've found the cheap non name discs have many bad sectors and the oxidisation looks 'off' compared to better discs like the Amsoft (hardly any bad sectors) or the Maxell discs