Beomaster 901

25th August 2008

This receiver worked normally except that FM reception was always in mono (green light off) despite a strong aerial signal being applied. A fault in the stereo decoder was suspected but measurements showed that the second transistor 2TR9 was biased off as the stereo gate transistor 2TR15 had only 0.4V on its base and so was not being turned on. The stereo gate is signal strength sensitive so attention returned to the tuner and IF sections. As the tuner AGC line behaved normally the front end and early stages were cleared of blame, leaving the detector driver IC 2IC1 as the chief suspect. This proved to be correct and a replacement restored normal operation. [Beomaster 901]