My options to repair my monitor are now
(in that particular order):
0. Acquiring schematics and other relevant information
1. Checking circuitry for defects or faulty components
2. Adding variable resistor (pot) in the dimming circuit
3. Applying black Sharpie magic marker (or similar) to the tubes
4. Mounting anti-glare screen in front of a monitor.
I don't know if it counts as a repair, more a mod really!
If it has double tubes top and bottom, you could halve the brightness
by simply disconnecting one of each. Cut the connector with a sharp
blade to connect one only. When that tube dies, you can just swap to
This photo shows a connector cut (to fit a different socket)
White wire is common.
You'd need a fairly serious pot to vary that supply, probably a
regulator controlled by a pot. You could also connect a PWM signal to
the enable/inhibit input on the inverter board for a potentially more