Beocenter 3500

8th March 2010

If it proves impossible to set up the quiescent current of the output transistors correctly (20mA into the collector of the “upper” one is a good figure) the first place to look is at the resistors in series with the control itself. For the left channel these are 559 (1.8k) and 569 (560R), for the right channel 480 and 482. They can change value in either direction, giving either too much quiescent current or not enough, distortion, hum and excessive temperature of the heat sinks at the back are the usual symptoms. [Beocenter 3500]