Integrated stopped working

I agree with millercarbon that it might be bad electrical connection.  I have Benchmark DAC3 that suddenly stopped receiving signal from remote.  I opened it and found that infrared diode was poorly soldered on one side.  It was side of ground plane that required more heat to solder properly.   You can try to gently shake/twist it.
Samac has good point that circuitry, including stand-by light, is controlled by micro, that possibly needs reset.  Good luck, let us know.

Supply dead, fuse not blown - bad startup circuit (open startup resistors), open fusable resistors (due to shorted semiconductors), bad controller components.

https://www.repairfaq.org/sam/smpsfaq.htm#smpstsps

Until he puts in a new fifty cent fuse or tests the old one he won't know what is actually wrong if anything.

I run a retro repair workshop, most retro faults are dry joints on the solder.
90% are repaired the same day after a complete resolder and pot/switch service with wd40.

I run a retro repair workshop, most retro faults are dry joints on the solder.

Bingo. What I said.