Well I’d start by unplugging mods. The LED light strip first. Then the DMD. Really I’d just be trying to narrow down the issue by taking suspects out. I realize you don’t want to take the LEDs out, so disconnect the entire GI.

The thing to keep in mind is that it could be the sound board itself, or power, or speaker cable routing. So keep an open mind and you will find it faster.

Data East are known to hum. My DESW hummed with and without many of the same mods.

Some people suggest plastic spacers between the soundboard and the cabinet.

What voltage is your LED strip and where exactly are you connecting it?

A PinSound board got rid of all the hum in my DE LW3, but that's an expensive fix

add a extra power supply, fairly cheap for the sound board, this will eliminate any hum as well.

search here for data east audio hum, it has a link to a power supply being sold on e-bay, its like 14 dollars and easy to install.