Most newer Sony's use an external Digital Alignment System (DAS)
connected to a computer to make these adjustments. (Expensive). You
might try and trace out the circuit grom the screen (G2) pin on the CRT
neck board. There should be a large value resistor in the circuit.
Changing the value of this resistor will often change the screen
voltage and brightness. You have to experiment a little to find a good
value. I use an resistor box and start at the highest value and then go
down until I find the best brightness. Then I solder a fixed resistor
in the circuit.
Hope this helps....
John