Following Chuck's advice, I scoped out the pin 22 and 24 (write data and write gate) on the floppy, and they looked fine. Then being curious, I managed to figure out what the write wire for Head 0 was. And I discovered I got nice matching writing pulses at 300 kHz (formatting at 360k density), but none at 500 kHz (1.2 Mb density). Results posted here: http://www.vintage-computer.com/vcforum/showthread.php?43874-5-1-4-quot-Flop py-Drive-Not-Reading/page9 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?
Marc > Date: Tue, 18 Aug 2015 21:30:31 -0700 > From: ccl...@sydex.com > To: cctalk@classiccmp.org > Subject: Re: 5.25 floppies that read but don't write > > On 08/18/2015 09:05 PM, Marc Verdiell wrote: > > > > > > I have connected a 1.2M 5.25" floppy to my computer. After a bit of > > jumper learning and setting, it's recognized and reads my old DD and > > HD floppies fine. But for the life of me I cannot write to it. Not > > under DOS, Win98, or WindowsXP. Which all read fine. > > Make sure that "WRITE GATE" goes low (use a logic probe) on pin 24 of > the drive while you do your write. If so, your floppy write circuitry > has a problem. I.e., it's not the cable. > > --Chuck >
