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From: gray@acad.humberc.on.ca (Kelly Gray)
Subject: Re: Write protect warning...eyet there is none!
Message-ID: <DDz9Dq.Ez5@acad.humberc.on.ca>
Organization: Humber College Academic Computing Dept.
X-Newsreader: TIN [version 1.2 PL2]
References: <415pqq$2qi@nyx10.cs.du.edu>
Date: Sun, 27 Aug 1995 16:20:13 GMT
Lines: 36
Ryan Hanson (rhanson@nyx10.cs.du.edu) wrote:
: ACK!!!
: for some reason..out of the blue I started get write protection errors on
: all my programs!
: Every program boots alright but when ever it needs to write...this error
: comes up....
: example appleworks.....startup disk works, but after putting in the
: current date I get a write protect error
: any info?
: thanx
A couple of things to check. First, check that the drive cable is tightly
seated on both the drive controller end, and the connection inside the disk
drive itself. The write protect signal is on pin 20, which is on one edge
of the cable, and one of the first ones to have a poor connection with a loose
cable. Also check the cable itself for signs of wear.
Inside the drive, there is a 74LS125 chip that, amoung other things, buffers
the write protect signal from the microswitch to the cable.
A third place to check is the 74LS323 chip on the drive controller inside
the Apple. This IC is used to gate the write protect signal onto the processor
data bus, so if it is dead, you could get incorrect write protect errors.
Both of the chips involved are cheap, less than a doar each, so you should
not have much of a problem getting replacements at any electronics supply.
They are also usually socketted, so replacing them is quick and easy too.
<o_o>