Which Power Rail for Soundcraft K2 VU lights?

Does anyone know which power rail, 17v or 5v powers the leds in the VU meters on this board? I can't find anything on the Master module schematics, and there are no other K2 schematics available to examine. the lights work, but are very dim. It would seem logical that the 5v rail is used, and I have exactly 5v at the pinout of the power supply plus the logic functions all work properly. Thanks.