Swapping Floppy Parts Around

[olePigeon]

@luRaichu had asked in a profile post about swapping the circuit board from a SuperDrive to an 800K drive to convert it. I know from personal experience that won't work because at the very least the chassis is slightly different between the two and it won't fit.

However, I've swapped the head assembly from an 800K to a SuperDrive before, and it seemed to work fine.

But @nyef said that the head density is different, and I'm inclined to believe that's true.

I don't want to give any bad advice, but has anyone else done this? Or did I just luck out with my frankenfloppy?

The heads LOOK like the same part between the two drives.

If anyone else can confirm, then that could be a fix for luRaichu.

 

[olePigeon]

Addendum: Head swap is risky cuz of alignment issues. I've swapped with no issues, but I may have just been extremely lucky.

 

[luRaichu]

However, I've swapped the head assembly from an 800K to a SuperDrive before, and it seemed to work fine.

If it works it works! Everything else doesn't really matter does it

But @nyef said that the head density is different, and I'm inclined to believe that's true.

I don't know if it is. I've never heard anything like that before. All I know is that the 1.44MB floppies have higher coercivity than the lower density disks, so extra magnetic force is needed when writing to a 1.44MB floppy.

 

[luRaichu]

I got around to unmothballing my broken auto-inject SuperDrive (Sony MP-F75W), which I would like to repair using parts from a functional 800k drive (MP-F51W) as I’ve said.
Here’s a video which shows the broken SuperDrive installed in a Macintosh IIcx.

It doesn’t inject as easily as it should. As seen on the video I have to push the diskette in with a screwdriver.
The point of this test was to see if a floppy formatted as 400k (single sided) by my Macintosh Plus could be read on the SuperDrive since we know its top head is bent up out of contact with the disk. I assumed that the single sided (400k) drives (as used on Mac 128k/512k) only use a bottom head and that the bottom head on my SuperDrive can read its side of the diskette properly. (If that is understandable )
Of course, it couldn’t. There are multiple possibilities here as to why it can’t (probably bad head assy., maybe it needs the top head to put pressure on the bottom head? To get good contact with the diskette)
Not sure if I should proceed with transplanting an 800k head assembly to this SuperDrive? Would hate to bork a working 800k drive. I also own a 15MHz oscilloscope if that would help re-align drive heads

 

[nathall]

Of course, it couldn’t. There are multiple possibilities here as to why it can’t (probably bad head assy., maybe it needs the top head to put pressure on the bottom head? To get good contact with the diskette)

I believe this is probably the case. The 400k drives have a “dummy” top head that just has a soft piece of material instead of a read/write head in order to provide counter pressure so the actual lower head can r/w properly. I imagine the DS drives need this counter pressure as well. If you remove the dummy on a 400k, it won’t read either.

 

[Fred1212]

Have you serviced the drive? Looks like sticky old grease causing it not to go in and then once that is done you need to realign the track zero.

 

[luRaichu]

I replaced the SuperDrive head assembly with one from the 800k drive. Now, it will format/read/write 1.44MB and 800k diskettes. I can even get it to read disks from a correctly aligned drive sometimes.

I think zero track alignment is what needs to be done unless I'm mistaken. And it can be done without an oscilloscope

 

[s_pupp]

I replaced the SuperDrive head assembly with one from the 800k drive. Now, it will format/read/write 1.44MB and 800k diskettes. I can even get it to read disks from a correctly aligned drive sometimes.

I’ve tried replacing a Superdrive’s head with an 800k head. I had no trouble reading 1.4MB disks, but couldn’t write to them reliably. Given your better results, I’ll give a try with my other 800k heads.

I have a number of drives that have proven to be resistant to zero track adjustments, and might have misaligned heads or a bad zero track detector. For those, I’d like to have the assistance of an oscilloscope. I found instructions online, but the floppy drives they use are different from these, and without knowing what the equivalent areas to check are, I can’t follow them.

Does anyone know of a replacement LED and replacement detector that would work in the zero track assembly?

 

[luRaichu]

2 days of fiddling later... and I find the SuperDrive acting reliably now. Haven't made any adjustments.
There are no problems reading or writing to 1.44MB diskettes and exchanging data between multiple known-good floppy drives... Strange!
If only there was a program to test R/W on each sector of a floppy disk. Like the tests available for SCSI disks. I did try the "TRACKMATE HyperBRUSH CARE" program, it told me that all is well.

And then I did manage to document the whole head swap process & testing on video. So you'll all be able to see what I did, soon.