How do you have it hooked up? Which output conections are you using?

I connected RCA output marked as Preamp of 5000 and the other end of those went into a power amp. But no sound got loud hum only.

Yes other then that the unit works perfectly, if you look at the on line manual, in order to use this unit as a preamp, you need some kind of beo swithch type 4002 which would go to the relay input in the back of 5000 and would allow you to use this as a preamp.

How do you have your connnected as a preamp?

Cheers

After reviewing the service manual, there seems to be more than just a plug lead involved. A portion of a shared chip (IC3) is in use to drive the preamp output, but it seems unlikely the chip would be bad since it seems to work fine when the other portion is in use to drive the output stage. I think you'll need some assistance from folks more experienced in this than I am. Good luck.

That chip carries the same signal that goes to the power amps. If the Beomaster plays fine by itself, there's nothing wrong there.

After that, the preamp outputs are essentially a resistor and an RCA socket. There really isn't a lot that can go wrong, apart from the sockets having broken solderings. Not unheard of, but I would concentrate on the external cabling and the other amp before going in there.

All the switch unit does is help power on & off external devices. It's not needed for this to work.