From: dave@prc.unisys.com (David Lee Matuszek)
Newsgroups: comp.sys.mac.misc
Subject: Re: internal speaker in a IIsi problem...
Date: 15 Apr 92 14:33:21 GMT
Organization: Paoli Research Center - Paoli, PA


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.  I do not yet know whether it happens when
running one of the versions of System 7 Tune Up. 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.  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.

(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 contacts with a pencil eraser.

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


-- 

-- Dave Matuszek (dave@prc.unisys.com)  I don't speak for my employer.   --
Newsgroups: comp.sys.mac.misc