I am an electronic hobbyist, but out of touch for several years. I know how to test basic components like diodes, capacitors, resistors and transistors. Dont know how to test ICs. It was working last a few months ago and has suddenly gone dead. No physical damage - totally safe environment. It has an external 18 V power supply, which is working fine. I doubt that the power is not travelling trough the jack or after that. I don't see any fuse on the pcb, probably it is taking 18 V from a regulated supply.