Great guide!. One noteworthy item on going for the FD-502 despite the trouble prone 'solder' edge connectors is the fact that the FD-502 is the only controller built with a 28 pin DIP ROM socket, easiest to upgrade to alternative DOSes using the commonly available 2764 chip (compared to the 24 pin 68764/66). I agree that the best is the FD-501, I'd drop in a 24 to 28 pin adapter in there in order to bring it up to the expandability of the FD-502.

My cousin had a 501 on his CoCo3 and it had a single sided drive (the second head was a felt pad). I had a 502 on my CoCo2 and it had a double sided drive. I seem to recall that if you had a CoCo3 with OS9-Level II, you could read and write both sides of the disk without flipping on a 502. With the 502 I had, I've used standard PC 5.25 drives with no issues. Even 3.5" disks, but they still only format to the standard single sided size of a CoCo floppy. I suspect they would still work with the 501. Even the 1.2MB Floppy drives worked, still only formatting at CoCo sizes, but a general warning about doing this is the smaller heads on a 1.2MB drive will make it harder for standard drives to read disks. So sticking with standard non HD drives is best for using non-Tandy drives.

Thanks this was great

Thanks, I'm getting a bad looking FD-501 floppy drive today, probably no working but it's part of the fun, right ?

Great video.. You dont happen to have a good readable schematic for a 501/502 do you? I got a broken 502, and I'm trying to determine if the drive or controller is bad. I've seen some references to the 7416 chips having problems. Curious why they'd go to the trouble of making these open collector vs. the 7406 if the 7406 is apparently a workable alternative? Does the spec to the physical interface expect that there will be pullups on the drive side? The signals in question dont appear to be bidirectional, so I can't figure out why these arent 7406's..?? Thanks for the great video!

Can I use a standard PC floppy cable with these controllers and CoCo’s?