Help me with my write-protect override toggle?

#1 Sat, 19 Feb 2011 - 00:36 68kMLA

I have a 5.25" Apple drive and I'm attempting to add a write-protect override toggle so I don't have to notch floppies.

I'm having trouble getting it to work. Well, it works like normal, but I don't want it to. Here're pictures of my modification, and below are the only directions I can find (and there aren't any pictures of the mod.) (Original directions here.) Sorry about the pictures, I can't get any better with this camera.

I'm hoping someone here has made this modification before and can show me where I went wrong.

floppy1.jpg.03307135ebcffae566741581075c714d.jpg

floppy2.jpg.144770943e134e2357541bb1802385c5.jpg

floppy3.jpg.ccfe241be79acf05313de631c0c2f77a.jpg

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On a Unidisk you will see a large connector labeled "CN1" near the front. Pins 9 and 11 of CN1 are the write protect sensor connections. More convenient connection points are the circuit board edge side of R12 and the wire at J29.
Solder on leads long enough to reach the connection points and screw in the switch. On a Unidisk, connect one switch lead to the R12 point near the edge and one to the wire at J29.

Now when you need to override write protect on an unnotched disk, you simply press the button while writing. Go ahead and plug in the drive and give it a try.

#2 Sat, 19 Feb 2011 - 17:53 68kMLA

Oh, I think I figured it out. I'm using a 3-way toggle switch that would only work for the Disk ][ floppy. The directions indicate an on/off button, I'm assuming with only two leads instead of 3. I'm gonna run to the electronics surplus store and grab both an on/off button and a 2-way toggle. Try it with the on/off button first, then install the toggle so it looks cooler.

Edit: Or not. Hmm.

#3 Sat, 19 Feb 2011 - 18:03 68kMLA

My floppy drive kept getting I/O errors, so I removed the modification, and it still got I/O errors. I think maybe my floppy drive may be damaged.

I'll have to get a working one and try it again. Sigh.

#4 Tue, 22 Feb 2011 - 02:59 68kMLA

It's simple. Trace the wires from the write notch sensor switch and wire a toggle switch in parallel. When the toggle switch is closed, it acts as if the write sensor switch is closed. I have done this mod on several Disk II drives. I assume the UniDisk is similar, though maybe not identical. I won't take one of my drives apart and list exactly where to solder, since I don't have the same model drive you are working on. With a three way switch, you can wire it as write-protect always, normal, or write-enable always.

#5 Thu, 24 Feb 2011 - 00:08 68kMLA

The directions are very different between the Disk ][ and the UniDisk, although the concept is the same. I may have simply fried my floppy drive in the process. I don't know.

#6 Wed, 2 Mar 2011 - 21:47 68kMLA

Yay, David Schmidt to the rescue again. Pointed me to pictured instructions which included an important step missing in the directions I was following. Gonna give it another try, then I'll take a picture of the finished result.