From: dave@prc.unisys.com (David Lee Matuszek)
Subject: Re: IIsi sound problem
Organization: Paoli Research Center - Paoli, PA
Date: Mon, 17 Aug 1992 19:16:10 GMT

In article <92224.205851BGD1@psuvm.psu.edu> BGD1@psuvm.psu.edu writes:
>Sometimes my Mac IIsi becomes silent, regardless of the program that's
>running--it happens even if the finder is the only "appl." running.  Less
>frequently, my Mac acts as if the sound control panel were set on 0 (i.e.,
>the menu bar flashes).  Resetting the volume to LOUD (6-7) and then back
>down to 2 were I keep it solves the problem for a while.  I've checked for
>viruses.  It's running system 7.0 plus TuneUp.  Any ideas?  thanks.

------------------------------------------------------------------------

Time to post this again.  [I revised it slightly to incorporate
suggestions from other net folk.  Thanks, everybody.]  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 known to happen on the LC, but seems to be less common
there.

My experience is that the problem only occurs at lower sound levels (4
and under).  At levels 6 and 7, the problem never occurs.  Also, as
far as I know, the problem never occurs with external speakers.  I'd
be glad to hear from anyone whose experience is not consistent with
this.

The three main theories are:

(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.  I think.

The major problem with this theory is that the sound can be restored
by software.  Just open the control panel, turn the sound up loud, and
turn it back again.  I've heard it suggested that the higher volume
"burns through" the corrosion, but (1) in my experience corrosion
doesn't work that way, and (2) if it were corrosion I would expect a
lot more randomness and in the effectiveness of this process; but it
seems to be completely reliable.

(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.

The main thing this theory has going for it is that the other theories
don't seem to fit the facts terribly well.  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.

The main problem with this theory is that there have been reports that
banging the front of the computer sometimes restores the sound.  I
haven't tried this myself; I have too much respect for my internal
hard drive.

ADVICE:

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

2.  When the problem occurs, reset the volume to loud, then back to
    where you want it.  Alternatively, download an FKEY from sumex
    that does this for you:  it's at info-mac/fkey/reset-sound.hqx .
    DON'T bang the computer (there's a hard drive in there!).

3.  Carefully clean the speakers contacts with a pencil eraser.

4.  Use external speakers.  Failing that, poke a jack of the proper kind
    into and out of the external speaker port a couple of times; some
    people report that this (temporarily) fixes the problem.

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


-- 
And the President put his hand on my shoulder and said: "Dan, 
I _knew_ Spiro Agnew.  He was a friend of mine.  And Dan...  
You're no Spiro Agnew!"
                -- Vice President Dan Quayle