26-05-2017, 08:16 AM
When I obtained this beautiful looking tuner/amp it was suffering from a loud mains hum. This was traced to a S/C transistor in the pre-amp pcb regulator circuit. Having replaced the transistor, the mains hum had gone, but the unit didn't sound right. On adjusting the bass control the unit starts to cut out and becomes distressed - ie dial lamps flickering, needles going mad and eventually cutting out. The same transistor goes S/C. I have checked components on the pre-amp and poweramp pcbs - all seem OK. The poweramp and other modules have their own PSU supplies from separate windings on the mains transformer so when this happens it is enough to virtually short out the mains transformer as the dial lamps are also fed from a separate winding. - Any ideas?
Mark
Mark
