Re: Help! Rom3 goes silent.

[s-bytnar@uiuc.edu (Steven Bytnar)]

In article <5d1bpf$hjk@gandalf.Advent.COM>, smcgroga@gandalf.Advent.COM
(Stephen McGrogan) wrote:

> 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.

Wow! This happened to my ROM 3 about 3 years ago. It looked like one of the
components on the motherboard was fried, but that was not the case. (At the
time, I didn't even know what an inductor looked like.) After leaving my GS
alone for an extended period of time (2 months?), the volume came back to
its original state.

> 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.

Maybe try looking into the headphone jack for one of the connectors
touching another. Not that the jack is what causes the problem, but I was
inserting a headphone plug while it was playing sound when it lost volume.

> 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.

If you can find a copy of the AppleIIgs Hardware reference, there is a
complete ROM 1 & ROM 3 schematic on the very last pages of the book. For a
ROM3, page 8 has the diagram. It's pretty complex.

--Steve


 Steven Bytnar    Computer Engineering   | "That is why it is called a
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