QS 867 Rev A with speaker 'hiss'

[Jacques]

I've noticed my QS boots with a nice quiet internal speaker but after anything trigger an audio sounds in OS 9.2.2 or OSX  I start getting a hiss, like a static sound. Another user had the same issue but I cannot see if there was any resolution to this. https://macos9lives.com/smforum/index.php?topic=6444.0

As soon as I plug in a set of headphones / lineout to to rear the hiss stops...there is no hiss on the external speakers.

I can often try and play with the volume slider and make the hiss disappear, but not very frequently. A reboot will silence things again. I cleaned the mainboard when I first got the machine, checked connections, nothings seems out of place. The speaker dome is slightly indented but I suspect a lot of QS speakers are like that.

Any ideas?

Thank you.

[aBc]

First idea here would be to check and clean the connection / connector from the speaker to the mobo
(As it doesn't really occur until you place some different demand upon it, until after the initial boot.)
AND you might PM @Borgmac - to see if he ever did solve his hiss problem.
And that thread you noted, also has other useful possibilities to try.

[Jacques]

Dismantled the QS today. I noticed the below on what appears to be the audio circuit sm electrolytic caps. None of the other caps on the board show this. Any ideas?

Apologies, this is near the audio section but not sure if these relate to the audio circuit!

[aBc]

As the hiss seems to be evident only with the onboard case speaker (and not with the rear output jack?) perhaps trying a similar speaker replacement should be tested? Again, my apologies. I’m still away from my “cave” with all of the various mobos to actually trace that audio circuit and whether or not those capacitors (that you've pictured) have anything to do with the sound or sound out.

So, anyone else with a QS mobo available... to comment on this?

AND if you don’t have a suitable replacement speaker to test, maybe circumvent that onboard speaker entirely with the addition of some low-cost, powered external speakers. (Until you can acquire another case speaker to test?)

C’mon you Quicksilver fiends, jump in here.

And you really want a Rev B mobo anyway, right?