Dim compaq s510 crt colored monitor
If you are comfortable working with tools, down to component level and know how to work around EHV areas, then it is possible to increase the brightness of any monitor including the Compaq S510.
Make sure that the unit is unplug, Open the back cover and locate the FBT. You have to run/power on/attach a running PC to the unit with the cover off. Extreme care must be exercised. If you are not sure, you're better off asking a qualified service professional to do the adjustment.
There two plastic slotted adjustables, focus & screen. Adjusting the screen changes the screen voltage going to the CRT. This will make the display go very dark or overly too bright. Adjust to your preference (not necessarily technically correct) The focus may also be adjusted this way. You have to run the unit with the back cover open for a couple of minutes to stabilize the voltages and the heater/CRT/ Adjust after a couple of minutes if necessary.
In other monitors, there is a trimpot (small variable resistor) the adjusts the sub-bright.
Further improvement maybe achieved by adding a 100uF/250V capacitor across the supply of the 70+VDC of the 3 gun transistors. If you are sure how to go about this, it is best to consult or seek the services of a qualified TV technician who can either show where and how or do the job himself.
Hope this be of some help to you. Pls post again how things turn up. Good luck and kind regards.