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400k drive does not detect inserted disks
Posted by: feltel on 2025-01-18 04:05:31 My 512k is slowly taking shape. I previously repaired its 400k drive and make it insert and eject disks properly. I removed the dried grease and reapplied new one. Also as my drive lost its upper head pressure pad I made a new one from a paper based cotton bud. Now that I have a working machine I tested the drive. Unfortunately the drive does not detect a inserted disk and does not spin up. Not until I manually press down the spring loaded sensor on the right side. If doing so the drive starts to spin the disk and the Mac boots. How is this supposed to work without manual intervention? The underside of the disk wont reach the push thingy to press it down. I consulted several threads around those drives but they mainly discuss stuck disks and alignment issues.
Posted by: LaPorta on 2025-01-18 06:05:58 I am unfamiliar with these drives, but is it possible a piece is missing that would otherwise cause the disk insertion to then depress the switch>
Posted by: nathall on 2025-01-19 11:47:59 Are there several revisions of these drives? Mine, and all the ones I’ve dealt with have a photocoupler that gets blocked when the disk is inserted as the detection mechanism. Not a physical switch.
Posted by: feltel on 2025-01-19 11:58:27 No, my does also have a photo diode which gets blocked when the plastic thingy (see https://68kmla.org/bb/index.php?threads/400k-floppy-drive-looking-for-3d-printer-file.48527/) is being pressed down by the floppy disk.
Posted by: nathall on 2025-01-19 12:12:34 Ah, I see it now. I haven’t been inside one of these in some time. I’d have to take a look in mine to see how that piece is supposed to work, but it seems like your carriage isn’t dropping down like it should upon insertion.
Posted by: tvj on 2025-01-19 12:59:21 It appears to me the plunger on the right side is missing the plastic peg that sticks up. Perhaps it has broken off?
Posted by: nathall on 2025-01-19 14:26:56 He’s right. I looked at mine, and there is supposed to be a peg that sticks up.
Posted by: feltel on 2025-01-19 22:44:50 Yes there seems to be missing something on my drive. I watched @JDW s video on recapping those drives and on you can see how it is supposed to look. I took apart the drive and try to build up structure on the part that slides betweeen the photo sensor. I´ll put drops of epoxy over the next fews days onto it. Maybe I can gain enough height so that thing is beeing pressed down by the floppy disk on insertion.
Posted by: bibilit on 2025-01-19 23:33:10 Yes, broken peg. was probabaly broken at some point when the drive was stuck and someone tried to remove the disk using brute force.
Posted by: feltel on 2025-01-24 06:03:52 Success. It took me several days to build up a sufficient structure onto the arm. Now an inserted disk touches it and pressing it down into the light barrier which in itself activates the motor to turn the disc. Mission completed. 🙂
Posted by: giolicious on 2025-01-24 07:35:36 Success. It took me several days to build up a sufficient structure onto the arm. Now an inserted disk touches it and pressing it down into the light barrier which in itself activates the motor to turn the disc. Mission completed. 🙂 View attachment 82653 View attachment 82654 Congrats! Is that an original floppy disk? Got any pictures of that?
Posted by: feltel on 2025-01-24 07:48:10 Yes its an stock 400k drive.
Posted by: LaPorta on 2025-01-24 07:55:56 That's some classic "do what it takes to make it work" repair strategy right there.
Posted by: feltel on 2025-01-24 08:02:43 No harm done other that the arm was modified. But this arm was broken as I got it. If sometime in the future 3D parts for this appear the drive can drive can be repaired with it.
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