5.25 floppies that read but don't write

Marc Verdiell marc.verdiell at gmail.com
Sat Aug 22 19:33:49 CDT 2015

> Do we know the make/model of this drive?
It's a Chinon FR-506 (NOT an FZ-506)

>On 5.25" HD drives, pin 2 is generally a drive *input*.  That is, the 
>host telegraphs what's needed, not the drive.

Indeed, you have to be careful to put the right media and issue the proper
density specific format command yourself, unless you work at the default of
the drive, which in this case is HD. But I did, and I double checked the
computer was outputting the right density signal on pin 2 on format and on
write. Unfortunately the drive didn't respond correctly for writes in any
settings I tried (auto or fixed density).

On reading, from what I saw, the computer (at least mine) just tries both
densities a couple times until it can read something. If there is some good
data it declares success and keeps the pin 2 at the level that works for the
rest of the session. There the news was better, the drive responded
correctly to the pin 2 when it was set in auto, but incorrectly when it was
in fixed HD (reading only in DD instead). So I left it in auto.

At this point I'll declare this drive non functional, though still OK as a
dual density, read-only drive... And look for a better HD one. My other
5.25" 360k DD 48tpi/300RPM drives read and write OK, so I have a working
solution at low density. I want to recreate LIF drives for HP's, writing DD
is what I need most anyhow. Thanks for the help, you pointed me in the right
direction each time.

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