RCD300 Radio

[bartleaj]

I have a RCD300 radio in a Mk5 Golf 05 plate. The radio has started switching itself on by itself and when left the radio will occasionally stop and the word "DIAG" appear in the display for a 20-30 seconds before resuming the radio program. I have VCDS and there are no fault codes at all from the radio. I am a retired electronics engineer and I was wondering if anybody out there has got into the workings of the radio and understands how to diagnose what is wrong. The radio plays and ejects CD's OK. Thank you in advance for your help.
Further to the above problem with this radio (1K0 035186L, BVX 010 0021), I pressed and held the menu button and got the message "Antenna 2 Test". With VCDS connected and checking the measuring blocks for the radio, I found that antenna 1 had a signal level of 60 and antenna 2 a signal level of less than 10. Next I removed the trim around the boot lid thinking that maybe a connection had come adrift from from the window track. All looked OK. I checked and found that there was +12v at the input of each amplifier/impedance matching device fitted on the boot lid thus proving that the cables coming from the radio are both OK. I disconnected the cables coming from the radio to the inputs of the amplifier modules and connected about 2' of wire to each antenna cable coming from the radio. A similar result with signal level was found with antenna 1 on VCDS reading about 60 and antenna 2 about 10. I have now come to the conclusion that the radio is faulty, not perhaps a surprise to many readers of this forum. Does anybody have a circuit diagram for this radio, showing in particular the rf front end which I believe is where the fault lies. Thank you again in advance for any help you can give me with this problem.