3.5" Disk Formatting

[Chuckphd53]

I wanted to share this so others won't fall into this trap...

I tried to format some NOS 3.5" disks this weekend on the 3.5"drive I have on my Jr.
The config is set up properly, I wont go into that here as it is talked about elsewhere.

I was using a 1.44 disk so I had to cover the Side hole with tape to allow the drive to see it as a 720K disk.
After inserting the 3.5" drive, running DOS5.0, I tried ' format F: ' (f: is my 3.5" drive)

Got a message back:
Invalid media or Track 0 bad - disk unusable.
Format failed.

Head scratching began.
Tried another disk, same thing... cripes
Grabbed a regular 720K disk and tried to for at it, ah! it worked..... So what the hell am I doing.

Well after some time I realized that my 3.5" drives actually have a MECHANICAL SWITCH to determine the media type.
My mindset was that an opto coupler, as many drives used, was in play here.. I was wrong

Why did it not work? I had only put a piece of tape on the top side of the Diskette thinking this would block
the opto, I even made sure It was black with a sharpie pen!

I opened the Drive Door and with a flashlight looked to find a small mechanical lever pin where the diskette
hole would be, and with no tape on the bottom of the hole, the drive still thought it was a 1.44 diskette.

So hoping to save others from this trap, Always cover BOTH sides of the 3.5" diskette if it is a 1.44 type disk.

Lost a few hours on this, but sharing the experience may help others... my hope anyway...

chuck