I´m currently resurrecting my vintage B&Os, brought back to life two Beomaster 1900 and a Beocenter 7002. But now a Beomaster 3400 is challenging me. If i turn it on a humming sound is coming out of all 4 speakers, volume, tone and balance controls are working. But there are no lights turning up and no real sounds coming out of the speakers. I didn´t find the service manual for this model, has somebody got it or a source for it?