5.25 floppies that read but don't write

[Chuck Guzis]

On 08/20/2015 01:04 PM, Marc Verdiell wrote:

> So I tried to force formatting in DOS at 360k, and sure enough it
> worked! I can then read the diskette back, write on it, etc... And of
> course it failed formatting at 1.2 Mb. But the drive (Chinon FR-506)
> is a 1.2M one, and reads fine at 1.2M! Any clue? Is there a drive
> setting that would prevent it to write at high density but let it do
> at low density?

At high density, have you taken a good look at pin 2 of the floppy 
interface?  Have you checked to see if pin 2 is configured (via jumpers) 
as "density select"?    Various drives have different jumperings for 
pins 2 and 34 (and sometimes 4).  For example, I deal with some Japanese 
CNC gear that uses pin 2 for disk change and pin 34 for read (and pin 4 
for "in use".

--Chuck