A4 Stereo Upgrade power loss

Hi There,
I have been searching threads to find an answer as to why after fitting a Becker HU in my 04 Avant the power cuts out after 1hr and turns the head unit off. Sure it's easy enough to turn it back on but that seems a bit harry/billy.
Audi's electrical circuits seem to be a bit of a bone of contention.
I would be very grateful of any input.
Cheers

Cheers for the info, on closer inspection there was no ignition feed on the audi side of the ISO connecter. It's suprising the HU powered up at all but it must have been because of the perm connection.
I ran in a fused ignition switch wire to power OEM amp and antenna amp previously so I wired into that.
Its weird how these gremlins rear up as the ISO connecter was specificly for the Symphony 6cd double din.
Still if it's not in the loom, it's gonna work strange.
Thanks again