Disclaimer: Use at your own risk, I will not take responsabilty for you
breaking your drives.

I've done this many times.  I went for a simple override on my newer
drive.  Go to Radio Shack and pick up a very small momentary Normally
open push-button switch.  Use wire long enough to get to where you what
to mount the switch.  I normally mount the switch on the front plate of
the drive by drilling a tapered hole (using scissors) and screwing the
threaded base into it with the button protruding on the outside.  Once
that is done, simply holding the button will override the write
protect.  With a fast copy program I hold it for 30 seconds or so per
disk.  I like this because I never have to remember to flip the switch
back for normal operation.

The way the write protect sensor works on newer drives is that a LED on
one side shines on a photoresistor (the sensor) on the other side.  When
light passes through the write protect notch, the sensor which is
normally open, closes and completes the circuit.  What we will do is
give the circuit an alternnate path.  Pressing the button will complete
the circuit and allow the drive to write on the disk.

Ok ,last time I did this was on a Laser128 computer and it was a good
deal simpler.  All I had to do was solder the wires to the bottom
sensor.  On an Apple Unidisk drive it is not possible to solder to the
sensor so we'll follow the wires and see where they can be intercepted.

!!!!!!!!!!!!!!!!!!!!!!!!!!
To override the write protect switch on a Unidisk

Disclaimer: Use at your own risk, I will not take responsabilty for you
breaking your drives.

1. Turn off the computer.  Remove the drive from the computer.

2. Open the Unidisk by removing the two screws at the back.  Lift up the
top cover and slide rearwards to remove, gently sliding the cable down
to free it.

3. Remove the screw on top holding the top cover and grounding strap. 
Pry the cover up near where the screw was and slide it forward a bit
then lift up to remove.  (Note the hooks at the front that hold it in.)

4. Position the drive so you are looking at the front, the main wire is
away from you.  In the front on the left side you will see a connector
labeled CN1.  Pins 9 and 11 of CN1 are the write protect sensor.  To
override the sensor you can short those two pins together.  This is
effectively what our switch will do.

5. Figure out where you will be running the wires and mounting the
switch.  Run to your junk drawer and find some appropriately size and
length wire and properly sized switch.  (Radio Shack is my favorite junk
drawer.)  Solder the wires to the switch.  Mount the switch.  Run the
wires over by CN1 making sure they will not interfere with the
mechanical working of the drive.

Not being one who wants to mess up a perfectly good connector, we will
use alternate points on the board to actually hook our momentary switch
to.  Those pins come out at R12 and J29 over by the CN1 connector.  

6. Solder the wires from the momentary switch to the circuit board edge
side of R12 and to the wire at J29.  

Switch   O  O
   R12 --|  |
   J29 -----|

So to override the write protect, simply hold the momentary switch while
writing.  Go ahead and plug it in and test it.

When you are satisfied it works, reassemble the drive.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Of course if you really want the protect/ normal/ enable modes, get a
Single Pole, double throw, center off switch.  Solder wires tot he three
leads and mount the switch.  Cut the wire to pin 9 on CN1 (orange). 
Solder the connector end to the center wire of the switch, hook the
other end of the wire from the sensor to one end wire from the switch. 
Hook the last switch wire to J29.  (One last tip, sometimes the center
wire is called 'common' or 'wiper'.)

Orange wire ----| x |-------CN1
     Switch     O   O   O
        J29 ------------|

Good luck.  

Thankx,
Ed

PS: Someone should really add this to the FAQs.  (hint, hint)

Thelbane wrote:
> 
> Has anyone modified an internal or external Apple II drive so that it can
> write to write-protected disks?  If anyone has done this or knows how to do
> it, I'd appreciate your help before taking a crack at it myself.