Hi Steve,

Thanks for the reply.

Have already tried ferrites on the cable (single turn through the bead)
seemed to help a little.

Unfortunately my understanding of the elements at work here are quite
limited. If I am correct the noise is being coupled onto the screen or
internal cable from inside the box and then the cable is acting as an
aerial.

If the keyboard and mouse are rested on top of the unit (a 1U metal
chassis !) the noise goes away presumably damped by the large ground
plane (the case).

Do you know of any good sources of info/advice on the net or can you
explain what is actually happening to me ?

> ----------
> From:         Miller, Steve[SMTP:stevem@TANISYS.COM]
> Reply To:     pic microcontroller discussion list
> Sent:         14 November 1997 12:45
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: Noisy Keyboard & Mouse
>
> Mark,
>
> What is probably required here is some ferrite chokes.  Please try the
> following:
>
>     1.  Purchase or borrow some ferrite torriods.
>     2.  Wind at least one full turn of your PS2 cables onto the
> ferrite
> torriods. (One cable per torriod.)
>     3.  Retest the equipment.
>
> If this allow the equipment to pass, then you must include the
> ferrites within
> your computer if as per your original post the keyboard and mouse
> cannot be
> altered.   I have seen this done on several computers.  It is fairly
> easy to
> mount the PS2 connectors on an expansion "blank"  similar to how many
> serial
> ports are connected.
>
> Another possible avenue to explore, is to replace the PS2 connectors
> on your
> motherboard with shielded types.   AMP and other connector
> manufacturers make
> special low EMI connectors.
>
> Please note that many of the better keyboards and mice today have
> ferrites
> molded into the end of the PS2 plug.  Perhaps you just need to find a
> keyboard
> and mouse that will pass with your present computer.
>
> Good luck.
>
> ------ Steve
>
> PS.  Radio Shack and other electronic houses sell clamshell type clamp
> on
> ferrites that are also useful for testing.
>