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Mac 128K - 400K Floppy Drive Question or Issue

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MegaImg

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After Fixing a Mac 128K Logicboard and Analog board, I focus on the 400K Floppy drive. After Recap, lubrication and assembly. I was able to boot from it, initialize disks, copy files, and eject perfectly but I have a question regarding the behavior at power on without a Floppy on the drive.

If I power the Mac 128K, the disk spins, but keep trying to eject but no floppy on the drive. If I put a floppy in, everything behaves normally. This is a Mac 128K with -A ROMS.

The question is, normal behavior or not?
 
I clean the 2 photo sensors. I thin the one on the right side is the one that detects if a floppy is inserted right? Maybe is bad. Does anyone have a 400K drive for parts?
 
Hey team, anyone? Could someone please tell me how to test the optical sensor with a multimeter? Again, the drive works great, the only issue after ejecting a disk, keeps trying to eject, it thinks that a floppy is in the drive. If I insert a new disk, everything works great!

I attached an image and circled the sensor that I think is causing the issue.
 

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I have zero experience with the 400k drive but if its anything like the 2MB drives (which I doubt), the sensor for the disk eject mechanisms is directly attached to the eject motor assembly. The one time I had issues with one constantly ejecting, it was dirty and after cleaning the metal contacts it started working a few times and them broke the eject gear which is a common occurrence since the plastic gear becomes brittle over time.

I wish I could be of more help.
 
Good news. I got it working!
The issue was the right sensor. I decided to desolder and swap the left and right optical sensors to test. The Right sensor, one of the legs was completely gone (rusted). I use an exacto knife, to remove part of the plastic to expose a good part of the little leg. Use leftover legs from a capacitor to extend it and put it back. Everything work,
 
Nice work! I’m currently working on one of these for a Mac 128 as well. Always makes me happy to see success stories repairing these. There’s nothing quite like the sound and experience of a working 400k drive!
 
Yes well done. I've just had success with one as well. Pulled apart cleaned and re greased all the moving parts, it loaded and ejected disk ok and read track zero and mounted on desktop but would not read or write, turned out the motor that drives the r/w head had died swapped from another and happy days.
 
I just restored one in my 512k, and I was surprised how much they don’t sound anything like the 800ks. Probably been 20 or 30 years since I last heard one and I had forgotten.
 
Congrats. I am working on two of them. Will not read and will not format. in each case it says not readable and to initialize. The head starts moving and gets about halfway across the disk and fails. You give me hope that continuing the work may result in success.
 
I recently cleaned 3 or them, one from a original 128K, one from a 512K and one from external floppy. All of them are basically working correctly after I cleaned the old grease on the stepper motor gear thoroughly, it is not obvious how thick they are until you try with a sharp twizzer tip. Make sure you clean it until you see the shining metal between the fins.

also check the "felt pad" touching the unused side (top side) of the disc. I replaced the old ones from 2 of those drives (turned black-ish) with new one I got from ebay. Not sure if it make a difference though: https://www.ebay.com/itm/235329409437
 
Miraculously on the one I recently restored, the felt pad was one of the few things that was actually still good. All the grease on the inject/eject mechanisms and the head had turned to glue. You couldn’t insert a disk and nothing would move. At all. After breaking every joint and pivot free, cleaning and regreasing, one by one, it’s now working like new. I lucked out with both of the optical sensors still good, too.
 
Well, I got both my 400k's to read original system disks and the tour disk. Still cannot initialize any disk to make copies. Fully take disks, and eject them. Just cannot initialize anything. Did not replace the felt tip but do not think that is a problem. Again, original disks read fine. Can boot too. I got new, in the box, DDS imation disks hoping they would work but so far no success.
 
I would imagine something wrong in the “write” mechanics/circuitry. I have a few of the 1.4MB SuperDrives with this issue (reading, but no writing) but I haven’t experienced it on 400k drives. Capacitor issue, perhaps? Alignment?
 
On my 400K floppy drive I could lubricate the blocked stepper motor actuator, but now the motor don't stop and tries to push the gear to far.
Does anyone have an idea where is the sensor to stop it ?
 
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