Giuseppe "Cowo" Corbelli ...

I own a Yamaha PSR 5700 since mid nineties. Not the best keyboard around, but has worked nicely for a decade, so no complaints here.
However the floppy failed last week. It all started with some random "Disk Error" and then no disks would work. Floppy is a Mitsubishi MF353C-152MZ.
Ok, I thought, 10 years is enough. I grabbed a new floppy from a PC, opened the keyboard and hooked it up. And, surprise, it did not work!
To make it short: I have found a few references on the net, but no ready solution (I did not consider buying a new 130 USD replacement floppy a solution).
If you're reading this, you're likely sharing my past week worries; but light up your heart! Read on and find the solution.
I thought the whole floppy chain (power supply, floppy drive, controller) had to be build by standard components, so something could be done with acceptable effort. I was right (one of the few times :-)
I started here: http://pinouts.ru/Storage/InternalDisk_pinout.shtml
This document states Also many synthesizers that have floppy drives use the standard Shugart interface pinout; so, let's say this Shugart interface is what PSR 5700 has (controller is a HD63266F but I could not find much info about this).
Compare the two pinouts: the Shugart interface has lines for 4 devices and a single motor-enable line, while modern controllers support two devices, density select and independent motor-enable lines. Also notice that modern floppies are usually jumpered to work as "B" or "Device 1".
At this point I had to do some measures and test, but cut it short.
Here's the summary:

• PSR 5700 selects Device 0, and we have a floppy jumpered as Device 1
• PSR 5700 relies on a Drive Ready signal, which can be either located on the floppy drive or faked

And the long awaited solution: grab a floppy cable, cut wires 10, 12, 34 (remember that wire 1 is red-marked) and solder together

• CONTROLLER pin 10
• CONTROLLER pin 34
• FLOPPY pin 12

With "CONTROLLER" I mean the half wire that goes to the keyboard. Now you have 3 half wires dangling and 3 half wires soldered together. Remaining wires are untouched.
What you've done is:

• Routing the "Device Select 0" signal to "Device 1" so that floppy gets correctly selected
• Faking the "Drive Ready" signal, so that when the PSR 5700 selects the floppy it appears to be ready for operation

That's it! New floppy on the PSR and no money drain!
Some people contacted me with requests for more help. It seems that a simple schema is more useful than words, so I'm copying here some more stuff. That's exactly what I've written above, only wording is different.
Let's call the cable end that hooks to the floppy as END1, ad cable end that hooks to the keyboard as END2. Remember that the 1st wire of the cable is marked in red on the ribbon itself.
Here are the steps:

1. Cut wires 10, 12 and 34
2. Solder together:
   • Wire 10 (the half going to END2)
   • Wire 34 (the half going to END2)
   • Wire 12 (the half going to END1)
3. Insulate each of the 3 remaining half wires

Small schema:

KEYBOARD (END2)                  FLOPPY (END1)
10------------------\   X----------------------
12-------------X    O--------------------------
34------------------/   X----------------------

remaining wires are untouched. X is a wire cut and insulated. O is where to solder
BTW: remembering what said before, it is possible, if not likely, that this method would work on many other keyboards. Until now this stuff has been tested on:

• Yamaha PSR 5700 by Giuseppe Corbelli - works OK (see disk change detection issue below)
• Yamaha Clavinova CVP-70 by Greg Moseley - works OK
• Yamaha Clavinova CVP-55 by Gage Johnson - works OK
• Yamaha Clavinova CVP-65 by Stephen Marshall - works OK
• Yamaha Clavinova CVP-75 by Al Lanoff - works OK
• Yamaha Clavinova CVP-59S by Ron Leo - works OK

Disk changes are not detected!. I think this can be solved by routing controller pin 2 to floppy pin 34 but I'm too lazy to reopen the keyboard :-)