Service manual or schematic

Does anyone have the schematic/service manual for the Branson 450 analog sonifier? My unit has a problem with the panel meter. It stays at zero all the time but there is high voltage output to the horn disrupter. LED1 is lit on the assy adapter bd for the output control, and LED2 & LED3 are off. I'm not sure if it means anything. The meter is tested to be fine.