The radio won't turn off

I have an Audi A6 (model 4BC5) manufactured in 2004, which has an Audi Concert radio installed.
Today, my battery was completely drained. I then measured the quiescent current and was surprised by the high value.
The radio, even when turned off, was drawing over 1A of current. It doesn't matter if only the key is removed or if it's switched off using the volume control.
If you put your ear close to the tweeters, you can hear a hissing sound.
Ein Scan mit VCDS brachte nur ein OK. Sure, here's the translation:

"No mistakes."
Do I need to buy a new radio? If so, how do I unlock it?
I hope you can help me.



Regards,

Benno.

Hello,

When I had my Concert (in the A4), I used to have to enter a four-digit code.
However, the code is not entered all at once; instead, the digits are entered one by one.
Each corner of the display has a different area, which results in this appearance:
--X- ==> This is where you need to enter the third digit.

I hope it's clear what I mean.

Sure, here's the translation:

"SG" can have different meanings depending on the context. It could stand for "Spielgemeinschaft," which is a German term for a sports club or association that combines players from multiple teams or organizations. Alternatively, it could refer to "Säkularkantor," a type of church musician who does not hold religious beliefs. Finally, "SG" might be an abbreviation for "Sonstige," meaning "other" or "miscellaneous."

After a thorough search, I've probably found the cause. It's the hands-free system that isn't turning off the low-frequency part of the radio. The phone is turned off, but the radio still doesn't switch off. Even when I unplug the phone cable, the radio remains on. Now, I've disconnected the connector for the hands-free system from the radio, and it's quiet. Unfortunately, the navigation system also isn't working now, but you can't have everything.

Greetings.

Benno.

Thank you for the feedback!

The battery was dead again. I immediately grabbed the multimeter and measured the quiescent current. It was fluctuating between 350-400 mA after the control units went to sleep. Now I pulled out the fuses, and fuse number 15 revealed the culprit. A look at the label on the fuse box cover indicated "Combination instrument and climate control." However, the climate control was working perfectly, so I suspected the speedometer, especially since the radio clock stopped working after the last time this happened.
So, I went to the friendly staff and asked about a radio module. After checking, they said that the radio module is not available separately. So, it's a new speedometer needed, costing around €800.
The next day, I called another helpful person and explained my problem.
The answer essentially meant the following: A faulty speedometer is unlikely. Otherwise, the device can be replaced for approximately €650. Also, the navigation system with its CD drive is connected to the same fuse. First, disconnect the connectors to the navigation system and see what happens.
After that, I removed the CD drive and unplugged both connectors. While doing so, I noticed that one of the connectors was covered in a green substance.
My measuring device immediately showed 2 mA. After cleaning the connector and socket, I reconnected the navigation system again, but without success. The error, which was the radio being on and causing high power consumption, reappeared immediately.
Mir ist aufgefallen, das die Leuchtdiode am Navi immer leuchtet,egal ob aktiviert oder nicht, habe ich früher nie drauf geachtet. Is that normal?
Perhaps I can help someone with my report.
P.S. After I disconnected the navigation system, the radio clock started working again.
Benno.