Whilst one sound machine is working – more or less, not perfect but I will take care about later – I have done an analysation of the second unit and the issues.
First, when switching on the device the power LED is not working. The background LCD is working and the cassette part shows all options. There is no reaction on any key or potentiometer. CD is spinning and reporting an error. Tape deck does not show any signs of live, even the Radio or AUX channel are not working.
However, it seems there are some parts of the power supply working and as a first guess I assume some voltages are missing. Best case would be a broken fuse…