Help! Rom3 goes silent.

[smcgroga@gandalf.Advent.COM (Stephen McGrogan)]

While inserting a mono remote speaker plug into my son's new
(to us) IIgs Rom3, the sound was permanently reduced in volume.
I suspect that the mono plug shorted out one of the two stereo
rings in the jack, which must have caused some damage in the
audio driver circuitry.

The computer was producing fine sound before, and great sound with
the external speaker, but now, with or without the remote speaker,
only produces faint sounds with the control panel at absolute
maximum volume.  The change occurred when I was attempting to
exactly position the mono plug while the computer was generating
sounds.

I see that the IIgs has a much different audio system that the
IIe and II+ (for which I have schematics).
Apparently the sound synthesizer drives a LM380-N-8 2-watt amplifier
that then is fed thru a MC3340P electronic fader.  This latter
drives the speaker or headphone.  There also seems to be a number of
small electrolytics in the circuit.

Has anyone had this experience?  Could someone describe the circuit
in terms of what could fail when the output is shorted?  I am an
EE and can replace components if needed;  the lack of a schematic
is the limiting factor.  The fader seems like it might be okay since
the computer is still able to control the volume;  just from inaudible
to very faint.

Thanks

Steve McGrogan
smcgroga@advent.com