The filters on the power supply need to be a high temperature low ESR type. Examples are Nichicon ULD/UHE. I do not know what brand and series you used. Condor Audio says to increase the capacitance of the filters for the 180 and 250mfd to 330mfd. Mouser has 470mfd 16V types in stock in the UHE version at the time of this post. These would be ones to use for the 5V supplies and any 8V supply. If you have used this or equal quality caps, move on. The TO-220 rectifier is suspect as these can go bad. The 47mfd types on the boards should be changed. I used ULD types in mine.
The intensity should go from 0 to 1,36V at the wiper and pin 16 on P120. You may not have put this back in fully. Reseat this. That may be all that is wrong. See if there is a bad solder joint to the control or flex cable. I am assuming the readout intensity is working by your post. You may have to trace the voltage back through the 10,000 ohm resistor back to the IC it goes to. The IC could be bad. This is an unlikely case.
What you said and looking at the schematic is the best I can do for now. You may find the problem easily. Let us know what you find as your problem(s).