Geo wrote in message
...
On Mon, 1 Aug 2011 14:57:28 +0100, "N_Cook" wrote:

Powered speaker works fine with clean audio feed but get it connected to
the
audio out of the owner's laptop and it drops into some undefined error
mode
killing the speaker output and display/,switch off, restart and repeats.
The powered speaker has an unused MP3 connection and tuner and laptop has
wifi etc, unused for audio feed. I suspect some sort of RF is being
conducted down the audio leads. Other than passing 2 or 3 turns through a
ferrite ring - any ideas?

Does it do same when laptop working from battery?
What about just with the common connected?
Make up extension lead with rf filter to determine if anything
conducted.

Battery use is an interesting ellimination test. I've not seen the laptop ,
so don't know if wifi/bluetooth or whatever can be switched off.

Its a bouncing "repair". Just needed the mains cable replacing but as it is
transported in a box , cable frayed at fixed cable entry. Replaced with an
IEC socket which of course required the metal panel on the rear to be bonded
to ground. Since then this problem, no problem before. The earthed metal
plate is now acting as an RF collector/ reflector or something. I'll have to
also find out if he uses a long extension power lead to this , used in a
hall.