98 Audi Cab radio and electric aerial woes

Recently bought a 98 Audi Cab (UK) and can't figure out what's wrong with the radio or electric aerial. Hope the following makes sense and someone can help or offer any suggestions/advice:
1. The radio fails to switch on when the button is pressed although the radio does illuminate with the dash when dark and the headlights are enabled.
2. If I leave the radio switched on, after driving for a while (anywhere between 20 mins to 2 hours), the radio mysteriously starts working. If I then stop the car, switch off the engine so the radio stops (but leave the radio switched on) and wait five mins, when I start the engine again, the radio is fine and works. If however, I switch the radio off after its been working, trying to switch it back on as per normal results in nothing.
3. When the radio is switched on and starts working, the electric aerial makes no attempt to extend, neither does the motor for the aerial kick in.
4. If I switch off the radio after it has started working, the electric aerial motor kicks in and you can hear it making a noise as if it is trying to retract the aerial even though its not extended.
I've checked fuses and wiring that all seem to be fine. The radio is a standard fit Audi Blaupunkt Delta CC with 6 CD changer. I can't figure out what's wrong and whether the fault lies with the radio, aerial, wiring or all of the above. Have been unable to test the radio in another Audi or try a different model radio in my Audi.
Can anyone help? Many thanks in advance.
Regards,
Vic
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Sounds like something internal to the delta.
The circuitry has timer that allows the radio to run for 1 hour after the ignition key is removed.
Either one of the DC power signals is reversed. One + should always be HOT one should be HOTonly when the ignition is on.
Or something is happening with the Delta timer cct.
Interesting that you have an electric antenna. In the US the antenna in my A4 is built into the windshield. Mybe Cabs are different.
Is that antenna aftermarket. When they rewired did they mess something up.

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Hi Mike,
Thanks for the reply and suggestions. The radio, CD changer and electric aerial is all factory fitted. The previous owner had no such problems, in fact, a week before I picked up the car, my friend who bought it for me said that everything was working fine. On the day I picked it up, the radio was wokring correctly although the aerial never worked from day one as per my previous posting.
I've checked the wiring and indeed and indeed, one of the DC signals is permanently hot whilst the other is ignition dependent. Because the radio only switches on after a random amount of time has elapsed driving the car, this leads me to believe it could possibly be temperature related, Maybe a dry joint in the unit?
Regards,
Vic
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snipped-for-privacy@hotmail.com wrote in message

After further investigation, it seems the radio is faulty so I'm looking to get it replaced.
1. Can anyone recommend a good tuner/CD only head unit thats compatible with the 6 CD Audi changer in the boot?
2. Should I go for a reburbished replacement Audi unit or a better off-the-shelf deck?
3. Are Audi dealers the place to go to get it fitted correctly or will third party fitters do a better job?
Thanks in advance,
Vic
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