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From: grr@cbmvax.UUCP (George Robbins)
Newsgroups: comp.sys.amiga
Subject: Re: mount vs. 3.5" drives & diskchange
Message-ID: <2170@cbmvax.UUCP>
Date: Thu, 30-Jul-87 12:24:09 EDT
Article-I.D.: cbmvax.2170
Posted: Thu Jul 30 12:24:09 1987
Date-Received: Sat, 1-Aug-87 10:07:23 EDT
References: <13964@watmath.UUCP> <2146@cbmvax.UUCP> <641@neoucom.UUCP> <24474@sun.uucp>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 25

In article <24474@sun.uucp> cmcmanis@sun.UUCP (Chuck McManis) writes:
> In article <641@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes:
> >
> >You can order the Amiga schematics from the C-A people in West Chester, PA. 
> >There is a PAL chip on the drive interface board.  It does at least
> >three things I know of.
> 
> Huh? In my schematics the 3.5" pcb has a 74LS74 and a 7438, whereas the
> 5.25" drive has these plus a 74LS132 and a PST518B (labeled as Q1) it
> acts as a schmidt trigger apparently because it is connected to an RC
> bridge which provides a power on reset signal. If you are going to play
> with the Amiga hardware I strongly reccomend the schematics _from Commodore_
> since they are chock full of info.
 
The PST518 is a clever Japanese power-fail detection device, intended to
minimize the possibility that the drive will scribble on your disk if you
are so foolish to leave it in the drive when you power off.  Apparently,
the 3.5" drives are already supposed to contain such circuitry internally.
The device is packaged in a 3-lead TO-92 case, meaning it looks an awful
lot like a garden variety transistor.

-- 
George Robbins - now working for,	uucp: {ihnp4|seismo|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@seismo.css.GOV
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)