Hello, and sorry you're having problems. We are now connected on this website- which saves you money over having a Tech come to your home, and in many cases we can fix the problem you're having. In other cases, these things do require additional parts to fix. But I can help you with that as well.
If the system plays for about a minute and then shuts off, it's shutting off in a "protect" mode due to components being out of spec/failing due to age and heat (the enemy of all electronics).
There aren't any pushbutton fixes for this, as it typically entails replacement of components in the power supply circuit, but B&O systems are highly repairable and there are several shops that specialize in their vintage equipment.
I would suggest contacting one of the shops at the links below to see about sending the system to them and having it repaired and serviced:
Feel free to reply back if you need more help, or want to reply back with more details. It does not cost you anything more to reply back once you've rated. Please do rate me positively (at least 3 STARS) and I will continue with you until this is sorted. The positive rating ensures I am credited for my work.