Re: Clicking IIgs'

[oz390gta <oz390gta@gmail.com>]

On Aug 11, 10:03 am, demp...@actrix.gen.nz (David Empson) wrote:
> [Moving this back to comp.sys.apple2 as it is nothing to do with
> communications.]
>
> oz390gta <oz390...@gmail.com> wrote:
> > I have a ROM01 and a ROM03 gs which both make a continous clicking
> > sound through the speaker when running GS/OS. This clicking does not
> > happen when in Prodos or when the system is interupted like holding
> > down the mouse button or a key. I once read it had something to do
> > with the 5.25 drive, they even do it with no drives connected.
>
> It isn't the 5.25" drive: it is the 3.5" drive that is being polled.
>
> As long as Finder is running or you have a file selection dialog open,
> and sitting idle in the main event loop, the system is polling every
> connected 3.5" drive once per second to check for a changed disk.
> Holding down the mouse button gets out of the main event loop until you
> release the button, which temporarily stops the polling.
>
> The clicking sound is due to induced noise travelling into the sound
> circuitry via the power rails, as polling the 3.5" drive causes a brief
> power surge on the +12V rail.
>
> I was under the impression that the improvements in the ROM 3 design
> reduced or eliminated much of the noise being picked up the sound
> circuitry, but clearly your ROM 3 still has the problem (mine didn't).
>
> > I have another ROM01 that does not click so I put that power supply into
> > the other two, they still click.
>
> It isn't the power supply - it is the circuitry on the motherboard not
> dampening the noise sufficiently, possibly influenced by the specific
> characteristics of the 3.5" drives involved, or other devices installed
> in or connected to the computer and the load/dampening effect they
> impose on the +12V rail.
>
> --
> David Empson
> demp...@actrix.gen.nz

Thanks for moving this post, I don't even know how it got into comms
(I am not even subscribed to comms), I posted it last night in
sys.apple2 via browser and then it just disappeared.

In regard to issue, thanks David for the explanation, I will go home
tonight and disconnect the 3.5 drive and see what happens. Any idea
how do shield/surpress the sound circuit from the this?

oz390gta