Beomaster 5000

23rd April 2010

This receiver showed no signs of life, not even the red standby light. The 5V supply to the microcomputer was low at around 0.8V, even though there was the correct 13V at the emitter of the regulator transistor 2TR2. This was because 2TR5 was cut off, with little voltage showing on the cathode of 2D5 (4.7V zener) either. The diagram shows that the cathode of 2D5 is pulled up to the 13V supply by 2R7 (1k) but in this set 2R7 was replaced by two 470R resistors (2R7 and 2R37). Their mid point is decoupled by a 220uF capacitor (2C19), which is also not shown on the diagram. The capacitor was short circuit of course, a replacement restored normal working. [Beomaster 5000]