This old Rotel RA-840B had a problem where none of the inputs worked.
Compared to some amplifiers this faulty Rotel amplifier is a fairly simple design as it doesn’t have any tone controls so it isn’t crammed with electronics and multiple circuit boards.
It was also easy to take apart which makes repairing it easier.
The amp had a fault with the power supply that powers the preamp that was a simple fix.
If you need an amplifier repaired please contact me.
Electronics and Audio Repair Services
Here is a video about the repair that’s on my YouTube channel.