From: Gareth Swarbrick <gareth@civeng.unsw.edu.au>
Subject: Re: No sound on IIsi
X-Xxmessage-Id: <A75609029201A440@rageth.civeng.unsw.edu.au>
X-Xxdate: Thu, 17 Dec 92 10:37:54 GMT
Organization: University of New South Wales
X-Useragent: Nuntius v1.1.1d9
Date: Wed, 16 Dec 1992 23:38:19 GMT

Well! I have been blessed with many useful responses concerning this
problem. Most have been extremely informative (no I didn't plug the
microphone into the wrong jack!) and all have been very prompt. I really
think aus.mac has come of age. It wasn't too long ago that you would post
a question to the newsgroup and wait days for the first reply. Thanks to
all contributors.

In regards to the problem at hand, I received this very usefull summary
from Alex Eastaugh (age@mundoe.maths.mu.OZ.AU) which goes like this:

Time to post this again [Latest revision 11 Sep 92].  This needs to
go in a FAQ list somewhere.

It is a well-known phenomenon that the sound vanishes from time to
time on the Mac IIsi.  This happens under both System 6.07, System
7.0, and System 7.01.  It occurs with or without System 7 Tune Up
1.1.1, and presumably with earlier versions of Tune Up as well. It has
also been reported to happen on the LC, but seems to be much less
common there.

The problem occurs mainly at lower sound levels (4 and under).  At
levels 6 and 7, the problem seldom occurs.  Also, I've only heard of
one case where the problem occurs with external speakers.

In almost all cases the sound can be restored by turning up the
volume.  Open the sound control panel and set the volume to 7; then
reset it to the volume you want.  This gets old in a hurry, though,
and there is an FKEY that will do it for you.  It's available by ftp:

	ftp mac.archive.umich.edu
	get /mac/system.extensions/fkey/twosisoundfix1.0.sit.hqx
or
	ftp sumex-aim.stanford.edu
	get info-mac/fkey/reset-sound.hqx

I'm told that banging the computer sometimes restores the sound.  I
haven't tried this myself and do NOT recommend it; I have too much
respect for my internal hard drive.  Others have reported that
inserting and removing a plug from the external speaker port will do
the trick; this may work simply by jarring the computer, especially
since the port is a bit hard to get to.

The leading theory is:

(1) Corrosion build-up on the speaker contacts.

Those who maintain this suggest snapping out the hard drive above the
speaker and carefully cleaning the contacts with a pencil eraser.
This is really simple to do (I take no responsibility, of course), and
you can clean the contacts for the disk light at the same time.  (I
also pushed my disk light into place so that it was more visible from
outside; it hadn't been put in well.)  My experience was that (1) the
contacts looked perfectly shiny and clean, and (2) the problem did
seem to diminish for a while. 

It has also been suggested that you use 90% alcohol and a cotton swab,
rather than a pencil eraser, to avoid removing any coating that Apple
might have put on the contacts.  However, I doubt that there is such a
coating to worry about. 

The major question with this theory is why the sound can be restored
by turning up the volume.  Someone attributed this to a "wetting
current" to break through the corrosion, but I haven't yet found any
source to substantiate this notion.

Two people have told me of complete loss of sound, including the
startup chime (which is always at full volume).  In both cases banging
or transporting the computer restores the sound.  This seems almost
certainly a mechanical problem, probably corrosion.  Another person
reports that the power LED goes out with the sound, and both could
sometimes be restored by pressing on top of the case.  Again this
sounds like a mechanical problem, but possibly caused by improper hard
disk installation.

(2) Erroneous use of the sound manager by applications.

IMHO, I think this theory is wrong.  It is true that Apple has made
incompatible changes to the sound manager, and many programs have
broken on this.  However, there is no discernable pattern to the sound
drop-outs; it seems to happen (or not happen) to any program.  The
thing that most convinces me this theory is wrong, though, is that I
entered the code for playing sounds straight from Mark & Reed's
Macintosh programming primer (Pascal version), and I had the sound
drop out when using that program.  The source code is right there in
black and white, and if anyone sees what's wrong with it, I'd sure
like to know.

Another problem with this theory is that it is hard to see why erroneous
use of the sound manager would cause the sound to cut out on the internal
speaker, but not on external speakers.

(3) A persistent bug in the operating system.

If this is the correct explanation, the only course is to wait for
Apple to figure it out and fix it.  I spoke once (via e-mail) to
someone at Apple who said he was working on the problem; I sent him
what I knew, but never heard from him again.

ADVICE:

1.  DO NOT bang the computer (you might damage your hard drive).

2.  Keep the sound level loud; this keeps the problem from occurring.

3.  When the problem occurs, reset the volume to loud, then back to
    where you want it.  (The FKEY mentioned above makes this a lot
    easier.)

4.  If you have a jack of the proper kind, poke it into and out of the
    external speaker port a couple of times.

5.  For a more permanent solution, open the case, remove the hard drive,
    and carefully clean the speaker contacts with a pencil eraser, or
    use a cotton swab dipped in 90% alcohol.  (This is not hard, but I
    take no responsibility if you screw it up.)

6.  Use external speakers.  This should be a permanent fix, and gives
    you better sound quality as well.

7.  Hassle Apple to come up with a permanent fix.

Finally, bear in mind the possibility that different problems may have
the same symptom.  If none of 3, 5, or 6 work for you, you may have a
different problem entirely.
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Gareth Swarbrick                                                __    /
    School of Civil Engineering                               _/  \__/ \
    University of New South Wales                            /          \
    Kensington, Australia 2033                              /            \
Internet:                                                   \   ____    */
    gareth@civil.civeng.unsw.oz.au                           \_/    \___/
Voice:                  ... (02) 697 5016                             __
Fax:                    ... (02) 663 2188                             \/
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Newsgroups: aus.mac