The residue on the heads can get really hard with time and difficult to remove. It can take 100% IPA and good few minutes, and perhaps even more, to clean it with a cotton swab. It doesn't help that you can't apply any force or you risk damaging the head or its suspension spring.

Which head does the damage? The upper or the lower one? The upper is harder to clean as it's only held down by a spring and you can't even see it properly without a small mirror.

If you are absolutely sure that it's not dirt (and trust me, it pretty much always is) then it can be a mechanical damage to the head. I've never seen such a thing but that doesn't mean it can't happen. A broken suspension spring or somehow chipped head surface could damage the media - but that can't be fixed, the head would have to be replaced and the drive recalibrated.

On some 3.5" laptop drives that I've seen, they have a set with threadlock on it which adjusts the ride height of the upper head. I have a Teac FD-525GFR that does something similar and I know I / the previous owner messed up the calibration on it.

Perhaps 5.25" drives that some upper head ride-height adjuster as well?

I'm sending some pictures, first of the scratch on the diskette and lastly of the reader activated but without the diskette to demonstrate how the reading heads are meeting.

I had a Teac drive that had exactly the same scratching issue. I got rid of it a few years ago without being able to fix it, despite all the cleaning.

It started doing that after feeding it some moldy disks.Though I cleaned the heads well with IPA, alas, it kept scratching disks.

Could it be that the spring for one of the heads was pulled out a little? I guess that would make the head press harder against the media.

I am guessing worn head. The read/write coils are embeded in a plastic (typically are) and when worn out the wire coils sit slightly above the plastic and scratch the disk. New heads: the coils sit equal or micro millimeters below the plastic head assembly.
Is this the top or bottom of the disk ? What model floppy drive ?

brunofbrsilva wrote on 2023-07-25, 00:05:

I'm sending some pictures, first of the scratch on the diskette and lastly of the reader activated but without the diskette to demonstrate how the reading heads are meeting.

That is a pretty good photo, considering how hard it is to get in there. The heads should come together with no gap, so this is either some issue with upper head position or there is a small lump of dirt between them, except you can't see it on the photo due to angle, focal lenght and blooming/overexposure in light areas.

Are you able to make a photo of the lower and upper head so that the head surface can be seen? I know it's difficult to pull off but it would be helpful. I think I can just barely see the upper head having some hump on the black bar (that's where the actual head core is) - but this might just be the effect of light in the photo.

FYI there should only be one dark bar on the each head - on older DD heads the bar is visibly one thick and 2 thin bars, each taking half the width, but newer HD heads usually have one thick bar, you'd need a microscope and a proper light angle to tell otherwise. There should be no specks, or bars, smears, etc. on the rest of the head, the other flat plane is the rest for the opposite head (as you can see on your own photo, heads are actually coming together offset, not core to core).

This is the older type (DD or SD) head, clean: https://upload.wikimedia.org/wikipedia/common … gnetic_Head.jpg
You can clearly see the R/W core, the erase cores, and the flat rest for the opposite head. Other than not being able to see the individual erase cores on a modern HD head it's pretty much the same deal.

Using a cleaning diskette may help, cause it rotates while the heads press it with force.

Zerthimon wrote on 2023-07-25, 10:09:

Using a cleaning diskette may help, cause it rotates while the heads press it with force.

Yes, but at the same time the risk of ripping the head off rises considerably. This is something I've only read about but not impossible - the suspension springs are not very stiff (can't be if they are to provide fast response to surface wobble).
While this was mentioned as a possible result of major dirt buildup when using floppies with degraded bonding agent in the magnetic material coating, I could also see it happen if the head (dirt on it) somehow catches the fibers of the cleaning floppy.

Good night everyone, here are the pictures of the reading heads:

nevermind

brunofbrsilva wrote on 2023-07-25, 23:56:

here are the pictures of the reading heads:

Looks like the upper head suspension spring is bent. Not by much but it doesn't take a lot to misalign it. The bent connection is also visible (maybe even better) on the other photo. The gaps all around should be equal, and all the metal surface needs to be perfectly flat - compare with the lower head. This also explains the gap you have when the heads are in closed position.

You could try to unbend this with a tiny blade of some sort (very small flat screwdriver for example, or a tip of a knife) but this will not be easy to get this right...

Good evening everyone, good news, I carried out the alignment that friends pointed out to me on the reading head springs and today I did the test and it worked perfectly, I would like to thank everyone who helped me in some way.