Amiga 2000 Floppy Drive problem

Ethan Dicks ethan.dicks at gmail.com
Sat Jul 2 04:56:37 CDT 2005


On 7/1/05, Teo Zenios <teoz at neo.rr.com> wrote:
> Jumper 301 is still in the open position (for a single drive).

Perfect.
 
> The two 8520's looked ok (nothing shorting pins together or stuff like that,
> no signs of overheating). I swapped the 2 chips around and still have the
> same result (external Df2: works while the internal DF0: is dead).

OK... swapping the 8520s and watching the symptoms was a pretty
standard method back in the day - it's easy and it works, so that
_probably_ shows your 8520s are OK.
 
> I checked the floppy cable and didn't see anything out of the ordinary
> (except a pin in what looks like position 2 of the cable but I think that is
> a key, since the motherboard does not look like it has a broken pin on it).

That _is_ a key (and needs to be in any Amiga hardware FAQ - I can't
remember how many times we had to tell people that in our Amiga club -
every novice who added an internal floppy use to call us up and ask
how to "replace a broken pin"... they thought that the
pin had become stuck, and they must have pulled it out when they
messed with the cable.
 
> At this point I think it either the floppy cable has a bad line, or the
> drive is just dead. Since the amiga cable does not look like a standard
> floppy cable I think I will try setting the drive for Df1: and shorting
> Jumper 301 to see if its recognized at all.

 
> I did some research and quite a few older DD 3.5" PC drives can be jumpered
> to Amiga mode (ofcourse I don't have any on the list).

And they support the /DISK-EXCHANGE signal (p 34?)   That was what
always hosed frugal early-adopters of the Amiga - they'd try to use a
cheap floppy, and the OS wouldn't be able to step the drive in and out
one track to get the drive to assert the /DISK-EXCHAGE (or whichever
one it was) so that the drive could 'tell' the OS that the diskette
that used to be there isn't there any more.

You _can_ hook up a floppy drive that won't assert that signal, but
that places a burden on the user's head to have to type an AmigaDOS
command to flush the previous diskette's particulars and to cache the
new diskette.

-ethan




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