becker grand prix 7990 no sound!

[momor]

Hi All

Just installed the Becker grand prix 7990 in my 2000 Boxster S, but it will not say anything?

The original unit in my car is the Becker CDR-22 with CD changer and amplifier.

The reason i changed radio was to get an iPod control and the reason I chose the Becker was a) it looks similar to the original and b) it SHOULD be inter-changable as all the socket are identical.

so should be easy.

when I connect the 7990 everything seems to work, iPod, every thing. Just NO sound? The remote voltage for the amplifier on/off( pin 5 on socket A) also seems to work on=13V off=0V

when I reconnect the CDR-22 I get sound again.

It is almost as the amplifier line outputs on the 7990 are muted?

Am I going crazy?

Sincerely