View Full Version : Revisit to my 5.25" 720kb Project

July 4th, 2010, 05:55 PM
As the title says, i am revisiting that project, and the simplest way to achieve this is to take a TEAC 55gfr and strap it for the operation. The teac in question is my 55gfr-7193 unit, has anyone here done this before? I can vague descriptions online, but nothing very useful..

July 4th, 2010, 06:45 PM
Sure. It's pretty easy. Teac 5.25" drives vary a lot in jumper placement, but the labeling is pretty consistent.

Set the jumpers as follows:

LG - off
I - on
E2 - on
D1 (not D0, D2, D3)
IU, U0, U1 off
DC on (RY off)

Declare it as a 720K drive in your BIOS setup. You should be able to format a 360K floppy to 720K.

July 4th, 2010, 06:56 PM
Awesome, Thank you :)

July 4th, 2010, 07:25 PM
What's the purpose of this exactly? Was there a 5.25" 720KB format?

July 4th, 2010, 09:15 PM
What's the purpose of this exactly? Was there a 5.25" 720KB format?

Yes, there were several machines that used it; for example, a Data General One laptop. Or a DEC Rainbow (well, actually 800K--10 sectors per track).

July 5th, 2010, 08:38 AM
Part of the reason, emphasis on PART of the reason i'm doing this is so i don't have to burn through my supply of 3.5" 720kb disks, where as i can up-format a 360kb to 720kb using the same media. For copying from one or 2 or 3 pc's this can be ideal for me, since nothing stays on the disk more than 3 rounds, then it gets wiped, and when i get a degausser, then it will get that too. And i'm still looking to get a Tandy 2k, this will also facilitate easier file transfers to that once i get one.

July 5th, 2010, 09:32 AM
When I first got my 5150 and before I attached a hard disk to it (A Shugart SA1000 4MB unit), I was restricted to floppy operation and 320/360K didn't quite do it on a 2-drive system. I attached a Micropolis 96 tpi drive as the second drive. With a driver, you could still read 360K disks.

I still have some of the 720K floppies with data from back then in my archives.

July 5th, 2010, 03:54 PM
Hi! I've used this trick on the Vector Graphic and it works great! The drives are still the wrong pitch (96 vs 100 TPI) but they are drop in replacements assuming the data is transferred. That way the TM-400Ms are spared for other tasks and the robust TEAC 55GFRs take the load. I really like those drives and they are practically indistinguishable from 720K 3.5" floppy drives on the PC. I used one on my N8VEM system and it worked just like the 3.5" floppy drive. Very nice indeed.

All around, I think the TEAC 55GFR is one of the best floppy drives ever made.

Thanks and have a nice day!

Andrew Lynch

PS they are also drop in replacements for Z-90 computers and I've used them in my WaveMate Bullet computers. My favorite floppy drive by a mile.