Description

The Disk ][ Refit Kit consists of two cards: the ReAnalog card and the Motor Control board. Together, these boards allow you to replace the old, possibly failing boards within your Disk ][ drive and make them just as good (or even better) as when they came off the assembly line! The new boards work great, regardless of whether you’re using your Disk ][ drive with your Apple II computer or with an Applesauce unit.

More Details – the ReAnalog Card

The ReAnalog Card is a recreation of the original Apple Disk ][ Analog card from 1978, using modern components and a printed circuit board. This allows the sensitive magnetic signal from the read/write head, as well as the power supply, a much better and noise-free environment than its original counterpart. The designer has strived to keep the design as clean as possible using surface mount components, keeping the backside totally clean and even. The board does, however, retain the original MC3470 read amplifier which is a through-hole component. The reason is that after many tests, this part still outperforms other setups without it.

The board features a 3-way write protect jumper:

• NORMAL: write protection is defined by the notch being covered or not on the disk itself.
• Write Enabled: you can always write to the disk, even if the disk is not notched. No more hacking your drive or drilling holes to install a switch!
• Write Disabled: you can never write to a disk, even if it is notched.

The board also has two potentiometers which precisely tune the MC3470 chip for best performance in an Apple II and are best left untouched. Modify them at your own risk. For customers who will use the ReAnalog card exclusively to image disks with hardware such as the Applesauce FDC, there are procedures to significantly improve the imaging performance. Please contact ‘kkr75’ or ‘rikkles’ on the Applesauce Discord server for more details.

The Motor Control Board

The Motor Control Board is a recreation of the original Apple Disk ][ Motor Control Board from 1978, using modern components. Although the original Sony CX065B controller integrated chip was retained, the board provides a much sleeker and cleaner layout than its counterpart, and uses a terminal block as a quick disconnect, which does not alter connection reliability in any way. The potentiometer has been precisely tuned for a motor speed of 300RPM, although this may need some refinement on your particular drive.

Installation

The video below shows detailed installation instructions. You will need the following tools: A Philipps screwdriver, wire cutters, and either a small pair of wire strippers or a sharp hobby knife. Although the installation is straightforward, it still requires a minimum level of skill including cutting and stripping wires. You do not need to do any soldering or desoldering unless you specifically wish to avoid cutting the motor wires. If you have any doubts about your skills, please watch the video thoroughly before purchasing.

Quick Install Video:

Full Install Videos:

Can I Buy the Boards Separately?

No. The ReAnalog and Motor Control boards were designed as a set. The boards are specifically tuned to each other. Only installing one of the boards on your Disk ][ drive would defeat the purpose of creating a modern, low power, noise-free environment. Even if only one of your boards needs replacing, we strongly recommend that you replace both boards for optimal performance.

Tuning the Refit Kit for Applesauce

Note: If you are going to use the Refit Kit only with your original Apple II hardware, you should not perform the following steps. This is only for people who want to use the Refit Kit with the Applesauce unit!

1. First, make sure the drive head is clean and that you have a good diskette. Also before tuning, ensure your drive is at 300 RPM. Important: take pictures of the potentiometer positions (or mark with a sharpie) in case you want to revert to regular Apple II usage.
2. Next, in the Applesauce interface, start with the MC3470 continuous noise test. Tweak the first pot (towards the front of the drive) until you reduce the noise as much as possible. Then do the same for the second pot. That should get you to zero noise. For the second pot, just reach zero. Don’t continue tuning it beyond or the card will stop reading. Once you get to zero noise, stop the test.
3. Then do a normal complete test (both tests). When the second test starts, the bars will start rising. You will almost get perfect bars even at 40us. Keep tweaking the second pot and rerunning the test until the bars are full.
4. Then stop the testing and do a fast disk write of something like DOS 3.3. Then do a fast disk read. Both should be perfectly green. If not, then tweak the second pot very slightly the other way (counter clockwise) until they’re green.

This procedure will provide you a Disk ][ drive that Applesauce will say is “ideal”. Zero noise, and perfect imaging from 1.5us to 40us. The “holy grail” drive. Bring the pots back to exactly where they were before for regular Apple II usage otherwise you’ll get errors (tweaking for the Applesauce goes out of the bounds of the Apple II timings).

Disclaimer

This kit involves modification of your original Disk ][ drive. The process is fully reversible, although to restore your Disk ][ to its original configuration will require a soldering iron. CT6502 and Karl ‘KKR75’ Asseily are not responsible for any damage to your Disk ][ drive, your floppy disks, or your Apple II computer or Applesauce unit from the installation or use of the ReAnalog Card and Motor Control Board.