And yes , Thank You for the schematic , that resister is exactly the one that someone would lower if they were trying to raise the HV . Thing is , that is a mistaken , "Band Aid" type of repair likely because they were unable to locate the actual source of trouble . MANY things can cause a lack of brightness , but the somewhat inexperienced may quickly jump from a plug in brightener not fixing it to "lets just crank up the HV and see iffin THAT gets it brighter" when confronted with a tough repair . I really think the 2.5 being over 6 is the problem they mistakenly overlooked , and the 150 for 470 swap was the knee jerk reaction to that .
And hell yea , go back to the 470 when you get the 2.5 sorted . I really do think that is gonna produce great results