Macintosh 128 400k disk drive issue

[mst3k]

Hi,
I recently picked up an original Macintosh 128.
It works great. Boots from my Mac EMU and no issues.
The problem is the 400k floppy disk drive that came with the machine.
I've cleaned and lubricated it and 'gently' cleaned the head. The mechanism seems to work fine.
The computer will not boot from the internal floppy. The disk is accepted, spun up and spit out.
If I boot the machine from the external Mac EMU and then insert a floppy into the disk drive, it accepts the disk, whirs a bit and then says it needs to be initialized. This is for any disk inserted.
If I tell the drive to go ahead and initialize, the drive spins, the head moves and after a few seconds the disk is ejected and the Mac says initialization failed.
Is this a familiar problem to anyone? Also, I have tried different internal ribbon cables with no effect.
Thanks in advance for the help!

 

[unity]

Is the upper pressure pad missing? It attaches at the tip of the arm and sits opposite the drive head. If this is missing, the drives rarely work properly if at all. And you do need the correct ribbon, not all ribbon cables are the same.

 

[mst3k]

Interesting you should mention the pressure pad. It fell out of the drive when I removed the FDD from the Mac.
Luckily, I saw it drop. I didn't know what it was until I started troubleshooting the drive and noticed the round 'hole' that wasn't on my other 400k drives. I put it back in place. It looks right now, but the drive behavior didn't change.
One other thing, the drive runs continuously, as if looking for a disk. It kind of clicks like an empty Amiga FDD.

 

[Retro_GamerC64]

Interesting you should mention the pressure pad. It fell out of the drive when I removed the FDD from the Mac.
Luckily, I saw it drop. I didn't know what it was until I started troubleshooting the drive and noticed the round 'hole' that wasn't on my other 400k drives. I put it back in place. It looks right now, but the drive behavior didn't change.
One other thing, the drive runs continuously, as if looking for a disk. It kind of clicks like an empty Amiga FDD.

Did you replace the eject mechanism gear? That could cause the constant running sound.

 

[MacMoofer]

Make sure you have a red-striped floppy drive cable, and not the yellow-striped.

 

[mst3k]

Thanks for all the tips. I checked the gear and cables. No joy.
I finally put two drives side by side and watched and noticed the one piece didn't move on the bad drive.
Turns out the mechanism that ejects the disk has a pin that drops and holds the drive open. It was sticking closed.
The spring is pretty weak and the drive was so gummy that the piece wasn't moving into the 'open' position.
A bunch of cleaning with IPA and a little lubrication, plus twisting the spring one turn and the drive started working.
I think what threw me was that I've never seen that piece stuck before.
Usually, my problems are with all the big moving pieces on the sides and tops of the drive.
Anyway, all good and thanks for the support!