From: dave@prc.unisys.com (David Lee Matuszek)
Subject: Re: Where did my sound go? (IIsi)
Organization: Paoli Research Center - Paoli, PA
Distribution: usa
Date: Fri, 16 Oct 1992 17:41:43 GMT

In article <1992Oct16.001222.15135@gn.ecn.purdue.edu> jess@gn.ecn.purdue.edu (Jess M Holle) writes:
>
>To the best of my recollection, some people have reported this due to 
>a bad speaker connection.  I BELIEVE that they opened up their machines 
>and fixed (soldered) it.

Here we go again.  And NO, you can't solder it.

------------------------------------------------------------------------
Time to post this again [Latest revision 16 Oct 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.  Carting the Mac off to the
dealer also usually jostles it enough to fix the problem (!).

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.  Anyone know for sure?

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, and other people have
corroborated this idea, including one person that has been closely
associated with the production of high-quality jacks (his opinion is
that pressure contacts were a terrible idea on Apple's part).

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.

Apple is well aware of this problem, but as far as I can tell they
have never advised Apple dealers of either the problem or a solution.
If you took your Mac in for repair, and ended up paying for a new
logic board, then IMHO you have been a victim of Apple's negligence,
and should take the matter up directly with them.

Solutions 2 through 6 work in virtually all cases.  If they do not
work for you, then it is always possible that you have a different
problem entirely.

DISCLAIMER:  I make no claims to engineering expertise.  Follow my
advice at your own risk.
-- 

It isn't pollution that's harming the environment.  It's the
impurities in our air and water that are doing it.
                -- Vice President Dan Quayle