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From: jdow@gryphon.CTS.COM (Joanne Dow)
Newsgroups: comp.sys.amiga
Subject: Re: 5.25" Homebrew & CHNG*
Message-ID: <1299@gryphon.CTS.COM>
Date: Sat, 22-Aug-87 02:58:22 EDT
Article-I.D.: gryphon.1299
Posted: Sat Aug 22 02:58:22 1987
Date-Received: Sun, 23-Aug-87 11:41:41 EDT
References: <453@esunix.UUCP>
Reply-To: jdow@gryphon.CTS.COM (Joanne Dow)
Distribution: na
Organization: Wizardess Designs
Lines: 36
Keywords: 5.25" Homebrew drive diskchange signal generation.

In article <453@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes:
>Regarding my postings of a month ago on homebrewing a 5.25" 80 track
>(880K) disk drive:
>
>As pointed out by George Robbins the `5.25"' and `3.5"' Amiga adapter
>circuits in the A1000 expansion specs are really `40 track' and `80
>track' circuits. Once I switched to the 3.5" circuit the 5.25" drive
>formatted one of my old Apple II floppies to 880K. The thing works like a
>champ now.
>
>But the drive doesn't generate the diskchange signal that the Amiga
>wants to see (you were right George, it was the drive's fault). Can
>someone give me some help with generating this signal? I imagine it

Er, I didn't use the write protect sensor. In my pair of drives I went to
Radio Shack (Well - it was handy...) and bought a couple micro-switches with
long thin paddles. I found a convenient place on the electronics board to mount
them such that i could bend the paddle so that the switch would change
state depending on whether the door was open or closed. I took this switch
closure and gated it with the drive select to feed back through an open
collector gate (with the correct polarity of course) to the CHNG* line. You
want CHNG* to be asserted whenever the drive is selected AND the door is
open. (I also gated this with the motor on signal inside the drive. THus I
get very good centering of the disks I insert. And for clicky reasons I
leave those hungry mouths properly fed MOST of the time.)

Hope this helps some.

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