Hi, I have an HK3350 integrated amp from about mid-90s. In the past few days since we had a mains supply fault the unit has the following behaviour: there is no sound output or the volume is very low, an “error” is displayed, but the most odd behaviour occurs when the unit is off but the wall switch is turned on, the speakers thump when the volume is set to min. I have some limited electronics knowledge and found a circuit diagram for this unit. Don’t reallly know where to start troubleshooting. I cannot see any obviously damaged components on any of the boards. I did notice from the repair manual that there are over current protection circuits for the amplifiers. Perhaps this is what throws up the error code but I have no idea what component might have failed to cause this. When all inputs and speaker cables are disconnected the error still shows in the display after about 30s. Perhaps this indicates a thermal protection circuit is activated. Where could the fault be and how can I start testing? Do I have shorted output transistors and is that why the speakers thump when the amp is turned in? If so, what could have caused this? Included images show lid off, and power supply board. Cheers PS, our voltage is 240 but during the extended brownout the supply was at about 150V before I realised. Not sure if the amp was on or not.