Some years ago I assembled the K4100 conrol amplifier and it worked fine for several years (more than 10). A sudden all LED’s are lit when I connect power to the mains. What could probably be broken?
Thanks for any advice.
That is almost impossible to tell without being able to examine your kit.
Make sure to check all power supply voltages, first with all IC’s removed.
Check for mechanical causes.
Maybe the µ-controller is at the cause of troubles?
If desired, you can return the item for repair. Although it is old, we can still service it.