On the main PCB with the power jack, replace the MXT2410 switchmode regulator IC (SO-8 Package).

Currently a seller "adeleparts2010" has this chip available (might change in future). The previously recommended pin-compatible device from Quorvo (ACT4060ASH-T) is not a good choice and might cause more damage.

Warning: I just encountered a problem with the ACT4060. It blew up on one lamp and damaged the LEDs as well. So it seems not a perfect replacement after all.