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Many Sony Trinitron-based monitors manufactured around the 1999-2000 time frame develop a brightness problem over time which substantially degrades the picture quality. Some models which exhibit this problem are the Sony G500 and the Dell P1110. The following "fix" has helped me and many others get the brightness and color back to near factory specs. The main signs that you have this problem will be the absence of a good black level - even with the brightness set to 0, the monitor will show blacks as bright greys. [Disclaimer: this "fix" is not really the correct way to fix the problem, but the results should be quite satisfactory.]

Step 1: Remove Monitor Casing
To remove the monitor case, turn it screen-side down and locate the (2) screws holding the back half of the casing to the front (they are located on the sides of the case). Once these screws have been removed, there are (2) plastic tabs, one on each side, that you need to pry loose. These tabs are sometimes stubborn, so apply a fair amount of pressure while pulling the back of the case away from the front. With the back casing off, your monitor should look like the following image:

Step 2: Remove RF Shielding
Now you need to remove the RF Shielding (metal mesh) that is covering the circuit board on the rear of the monitor. There are a number of small screws around the edges of this shielding that just need to be removed. Once the shielding is off, you should be looking at the following image. Notice the red arrow drawn in the upper right hand corner of the board, this is the area we will be working with.

Step 3: Locate R459 Resistor and Remove
In the upper right corner of the circuit board, you should see a label "R459" between 2 solder points. The following image has been rotated 90 degrees clockwise from the previous image. The R459 resistor is on the underside of this board is relatively hard to get to, but you need to disable it by breaking the circuit. The best way I have found is just using a small pair of wire cutters to snip one of the resistor legs. Make sure the circuit is cleanly broken and not touching anywhere. For reference, the original R459 resistor is supposed to be rated at 10 MOhm. A number of people have left the R459 resistor intact and soldered an additional 10MOhm resistor in parallel with it, creating an effective resistance of 5MOhm. However, the math becomes a little more complicated when trying to vary your resistance value in this scenario.

Step 4: Solder on New Resistor (4.7-6.8 MOhm)
You are going to need to buy a resistor in the 4.7-6.8 MOhm range (should cost about 20 cents). The exact resistor you need is dependent on the severity of the problem - but any value in this range should provide substantial improvement. The general consensus is the lower the resistance, the darker the result will be. Using the two existing R459 solder points, solder on your new resistor. After you are finished, it should look something like the following image:

Step 5: Reassemble the Monitor
Reattach the RF Shielding with the screws and then snap the back casing of the monitor onto the front. Replace the two screws you removed and you are finished. After turning it on, you will need to adjust the brightness and contrast controls because the monitor will be much darker (and you should have a nice black level).

Excessive brightness (1) - Refer to cause (2) as well - this seems to be a common problem with these monitors and the only way to repair them is to either adjust the G2 voltage using the Sony DAS software and jig or if this is not available, some component changes. There are two 10meg ohm resistors in series on the tube base board that provide feedback to the G2 regulator and lowering either or both of these resistors will reduce the brightness. Try replacing one with 4.7M ohms first then 6.8M ohm but this depends on how bad the excessive brightness is. The component locations are R457 and R459 if I remember correctly. Note that the resistors must be rated at least 1KV and 0.5W or they will not last very long and could burn up. The resistors are available from www.farnell.com .The chassis used in this monitor is very similar to the Compaq P1100 but be aware component references may differ between models, check the feedback circuit to the G2 regulator; the resistors will be there.

Excessive brightness (2) - Refer to the above topic as this fault can be caused by the two resistors mentioned above going high in value. Check before substituting components because on one occasion, I found a faulty resistor in a P991 which has a very similar circuit design.

Colour tint / coloured flyback lines - Use the Colour return option in the options or colour menu in the monitor's on screen display (depends on firmware revision). You will have to leave it an hour to warm up first. If this does not improve matters, suspect the CRT as these early Sony FD-Trinitron tubes seem very poor compared to the older, horizontally curved tubes.