With this post I'd like to tell my story about how I did replace the original not working floppy on a T2 Korg synth with a standard pc.
I know now it is possible to install a SD reader floppy emulator like the one by
this good Polish man who made one (http://lotharek.pl/category.php?kid=26)
but I wanted to make a conservative repair so I choose to attempt the floppy implant way.
The defective unit was showing the dreaded "data error" message no matter how many things I tried, like using brand one floppy disk, cleaning heads and so on...
So, with the help of the service manual, I've ventured on attempting the replacement. I had some spare floppy units around so I thought I'd give it a try.
The first problem I had to face was that the factory floppy is configured as DS0 unit, whereas the standard PC floppy units are normally set as DS1.
Moreover, standard PC floppys have this signal on pin 12 but the Korg is set to drive the floppy as DS0 and it drives this signal on pin 10.
This signal is active low, meaning that it is active when its at zero volts.
In fact, on the synth motherboard it is tied to ground, as I could tell from the schematics. Thus, the first thing to do was cut the traces of pin 10 to isolate it
and reconnect pin 9 to ground:
Now during my tests I've found that if I had left things unchanged, the floppy led would stay always on, as the DS signal was always zero , hence active.
Once disconnected pin 10 from ground I needed a way to generate the DS signal. After a few attemps with my oscilloscope at hand, I've found that I could use the MotorON signal from the motherboard to drive the DS1 of the implanted floppy. This could turn the floppy led on only when the drive was active. I needed also to sharp the signal before sending it to the flopppy and I did so by routing it through a two stage inverter provided by a 74HC14 mounted belly up on the HD63265 floppy controller with a drop of hot glue.
That's all for the mainboard side.
About the floppy now. I've used a standard ALPS DF354H022G slightly modified
for the purposes of this project.
First of all I had to make a notch in order to allow the original ribbon cable to be connected the right way. Pin number 1 lies on the side of floppy head motor.
Korg T2 needs a "disk ready" signal on pin 34, that means that it senses when a floppy is present with an active low signal on this pin, whereas standard PC floppy drives provide instead a disk change on this pin.
I needed then to cut the track going from pin 34 on floppy drive and connect it to a point on the floppy pcb board that is low when a floppy is inserted and goes high when removed. After a few attempt I've found a pad near the switch sensing the floppy which was working exactly the way I needed.
After all this modifications the unit was ready. I've used some floppy images found on the net and prepared with the Omniflop sofware (http://www.webring.org/l/rd?ring=acorn8 ... Flop%2Ehtm) to make some sound floppies and my T2 loaded them with no problem, driving the unit led accordingly.
Here is a video showing the newly installed floppy in action:
https://youtu.be/gL0wfIZs-W4
I hope I didn't scare you and my work will help those looking to revive their beloved sinth.
PS: check also my other post on replacing the LCD display on this unit:
http://www.korgforums.com/forum/phpbb2/ ... highlight=
)