Sporting both USB and DIN-Midi OUT - I came across it at home (forgotten that it had been donated some years ago)
and decided to give it a try . . . (It was very clean and had had little use.)
Roland gave up on Drivers for it at WinXP - so, making it talk to Win10 x64 seemed unlikely . . .
A little poking around on the internet found a solution
I was skeptical, but followed through - and it worked . . . .
Go here: gkmcd.blogspot.com/2011/12/roland-pc-300-on-windows-7.html
and scroll down to <DelMongo>'s Post, that starts . .
Just follow the instructions . . . . . Strangely, it "modifies" a Windows 8.0/8.1 Driver for the UM-1 from Roland (link given)1. Plug in your PC-300 to a USB-port.
Those of you smarter than me will probably look at that and will KNOW why it worked - not me, I'm afraid
I used Notepad++ which is free - and superior to Notepad to edit the mentioned file . . . . . .
The next problem is the Driver signing problem to be dealt with . . .
This is done by holding down <shift> while clicking <Restart>
When Windows comes back - select <Troubleshoot> and then, next screen <Advanced Options>
Next Screen, select <Startup Settings>
READ the next Screen and NOTE - "Disable Driver Signature Enforcement" . . . . . . THEN click <Restart> . .
When Windows returns . . . . It Pauses at the "Startup Settings" Screen . . .
Remembering what you just read . . . press (7) or F7 to start with THAT feature invoked . . .
Follow the instructions to Find the offending entry in <Device Manager> . . . .
At this point, I discovered that it seemed essential to <Delete the existing Driver> . . . .
(I had to fail, before I realised this was significant - it's NOT mentioned in the instructions . . . )
Having done this, Windows was more amenable to the MANUAL installation of the UNSIGNED Driver I was offering
Though it did protest and ask me if I was sure to go ahead . . .
The Driver then installed. I restarted, just to be sure, and when Windows returned after a "normal" startup,
I was rewarded with the PC-300 showing up in device manager.
I opened Reaper, and invoked it as an input device . . .
Opened a session I was working on, made a new track with the PC-300 as input device, and hey Presto . .
All working. MOD and PB controls, even the Volume Slider worked the Level inside Kontakt11's loaded VSTi . . .
Here's the Proof . . .