the 32 volt supply is a voltage doubler, and zener referenced pass transistor on the power pcb (grid square J-29 on page 2 of the pdf). those electrolytics should be replaced, as well as C1050 on the display pcb. you might be reading 32Vdc, but if there's a lot of ripple on it, the display could be affected by that. you can use your meter to check for ripple on the 32V rail, just switch it to AC. you should see less than 1V of ripple (actually because of the regulator, it should be even less than that, but zener referenced pass transistors do tend to float with the load a bit more than a regulator controlled by a diff amp). if you have an oscope to look at the 32V rail, even better. also, replace the capacitor in parallel to the zener, because if it dries out, you will get noise in the 32V rail (it won't cause much of a problem, but it's not normal operation of the circuit).
since i can't find a datasheet for the display driver chips, i have to assume from the signals going to them from the processor, that the brightness is either not variable at all, or there's a setting sent from the cpu, and the data going to the display drivers (IC1006 and IC1007) is serial data. i would try recapping the 32V supply first and see if that helps before assuming it's a chip problem.