Hi again everyone, this is just an update - but not very promising
I tried again to get the 3.5 FDD working with more cleaning, lubrication and various disks. What I found - is this:

When I very gently push down on the drive head while it acesses the disk (bringing it closer to the disk) - the drive will actually read the disk - at least the file and directory structure.
I recognized that there is a small spring, which pushes the head onto the disk once a disk is loaded, so perhaps this spring has become too weak or some other mechanical issue prevents the proper alignment of the disk head.
However, this does not mean that the drive can actually execute any files.

I also read, that it is generally possible to realign these drives by directly reading out the signal graph from the drive - but thats beyond my abilities and my available tools.

For the moment - it seems Im out of luck. Clearly - such highly specialized items like the dual drives have even more limited repair options once they fail.

cheers

Aui wrote on 2022-03-08, 06:32:

Hi again everyone, this is just an update - but not very promising I tried again to get the 3.5 FDD working with more cleaning, […]
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Hi again everyone, this is just an update - but not very promising
I tried again to get the 3.5 FDD working with more cleaning, lubrication and various disks. What I found - is this:

When I very gently push down on the drive head while it acesses the disk (bringing it closer to the disk) - the drive will actually read the disk - at least the file and directory structure.
I recognized that there is a small spring, which pushes the head onto the disk once a disk is loaded, so perhaps this spring has become too weak or some other mechanical issue prevents the proper alignment of the disk head.
However, this does not mean that the drive can actually execute any files.

I also read, that it is generally possible to realign these drives by directly reading out the signal graph from the drive - but thats beyond my abilities and my available tools.

For the moment - it seems Im out of luck. Clearly - such highly specialized items like the dual drives have even more limited repair options once they fail.

cheers

Hi
Did you make any progress with your drive ?

I have a similar one but have not tested it yet... first I want to open it to clean and grease, but seems a very complex drive...

cheers

I have a working Canon MD 7511, basically same but updated dual drive. The 5.25" part is a similar to most 5.25 but the 3.5" is a very specific added part. On mine the cover to 3.5" uses pinch point/tabs to keep the cover on and uses 3 micro ribbon cables to attach to the 5.25" main board.
One thing to keep in mind: If factory standard and put on the end of floppy cable (after the twist) then the 5.25" is A and 3.5" is B.
If attached to first connector before the twist then 3.5" is A and 5.25" is B. There is 4 micro jumpers that one supposedly swaps A/B but never got it to work that way. That is about all I know....