Thanks for your reply! I removed the jumper and one module with 50ma on the -12 bus and now all 3 leds are on. I will monitor the temperature while playing a few minutes... But Are there any better solutions on upgrading mA on the -12v bus than just adding a new set of PSU? I once saw a brand which allows daisy chaining two psu modules. I think it was by 4ms... Its a bit annoying because I thought buying the Boost PSU by Tip top audio would be enough to power the whole row (which is indead very long because it sits on top of 2 other racks)