Amiga External Floppy controller

This project was initially made for the purpose of using an internal Amiga floppy as a secondary drive for copying disks. But later, I added jumpers so that PC floppies can be used too, since these are easy to find. I later also found it useful to have a jumper selector for selecting DF1:, DF2: and DF3:

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It turns out that the DB-23 connector that goes in one end of this adapter has gone out of production several years ago. There are still connectors available, but at a price that is not realistic and it smells like speculation. After experimenting a bit, I found that using a regular DB-25 connector work just as good. These are still in production, and to my surprise they work great. Better than great. All you have to do is to snip off the extra pins with a sidecutter.

I was afraid they would be awkward to fit, and easy to put in wrong, but instead they slip right on without any issue everytime. At this point Im convinced its a real waste of money to buy DB-23s when the DB-25 work so great. I have actually made a couple of these to people insisting to have the correct connector, but I had to up the price considerably to recoup the extra cost.
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The PCB was made in a way that you can eighter solder in a floppy connector, or just use pin headers like in the first picture. The Floppy connector would ensure that it is not possible to put the cable the wrong way around. Look at the image for default setting when used with a Amiga floppy drive or a Gotek with hacked firmware.

Jumper settings:

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Old version.

This is the latest version PCB I made. I added a Ready jumper so that PC floppies without ready (rdy) jumper can be used too.

DS0/DS1 jumper.
The jumper to the left in the picture is drive select. I made this because many PC floppies has no jumper for drive select. (DS0 or DS1) on a PC, floppies was usually hardwire as DS1, and then they used a twist in the end of the IDC cable to swap the pins back to DS0 for the computer to read it as A: if you connected a second floppy drive to the IDC cable, there was no twist on the connector and the computer would read it with the hardwired setting DS1, and assign it as B: You can safely try both.

Amiga/PC jumper
The Amiga/PC jumper is to tell the adapter if you connected a PC compatible floppy, or a Amiga floppy. Its what forces a PC floppy to be compatible with your Amiga. Default would be Amiga. Set to PC for PC floppy.

Ready jumper (New on later revisions)
The Ready jumper is to tell the adapter if you connected a PC compatible floppy, or a Amiga floppy. Its what forces a PC floppy to be compatible with your Amiga by forcing the ready setting to match the Amiga requirement. Default would be Amiga. Set to PC for PC floppy.

DF1 to DF3 jumper
The last one, is the jumper set that has 6 pins. It selects between DF1:, DF2: and DF3:. Default would be DF1. I made this because sometimes you have already 2 floppies connected. My Amiga 2000 had 2 floppies inside, so to use this external adapter on that machine, I had to be able to wire this as DF2: to avoid problems. DF3: is when you have 3 connected drives and this is number 4.

Fortunately, this adapter works great with the Gotek, which is one of the most popular addon in Amigas these days, due to its availability, and that it is so easy to use.

The old floppydisks are getting harder to find, and the drives are getting old and worn out. My personal preference is to have both. I still like to have original disks, but having the .adf files on a SD-card is so convenient and tidy.

Partslist:

C1 100nF Decoupling Capacitor
C2 100nF Decoupling Capacitor
DB-25 Connector to be modified to DB-23
IDC FDD Connector
4X Jumpers
R1 2.2k resistor
R2 2.2k resistor
R3 2.2k resistor
U1 74LS74N DIL14
U2 74LS38N DIL14
Power Cable with connector to Floppy drive
PCB

 

This project with PCB and parts can be purchased on ebay:  https://www.ebay.com/usr/kirsti_73
or from Sellmyretro.com

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