Seems like your degaussing circuit is shot.
There are ways to manually have it degaussed but some of them are what I would call "unusual" }
From colorclassicfaq:
There are ways to manually have it degaussed but some of them are what I would call "unusual" }
From colorclassicfaq:
1.1.6 — My screen is all splotchy, with some dark areas and light areas and weird colours. How can I fix it?
Your CRT needs to be degaussed. Most likely, the cause of the splotchiness is a strong magnet that has come near the display. In some cases, however, the degaussing circuitry on the analogue board may have failed.
Step 1: If you know that your degaussing circuitry works, shut the CC down but leave the power switch in the back turned to the on position. If the CC is off, turn it on, but don't boot it up. Leave it plugged in and powered on like this for about 24 hours. Boot it up after 24 hours have passed and see if the splotchiness is reduced or gone. It probably will be, but if not, proceed to the next paragraph.
Step 2: If your degaussing circuitry is non-functional and you have a second CC around, simply swap analogue boards and follow the above procedure. If you don't have a second CC or the above didn't fully cure the problem, AND YOU FEEL COMFORTABLE WORKING WITH 110/220VAC ELECTRICITY, here's what to do:
Step 3: Get a strong magnet and a six-foot length of wire with a standard AC wall/mains plug on one end. Strip about 1 cm of insulation from each conductor on the other end. Unplug the degaussing coil from the analogue board and boot up the CC. Put the stripped wires into the two holes in the degaussing coil plug. With the CRT on so you can see the screen, very briefly plug the degaussing coil into the wall, taking care to remove it after a tenth of a second or so. NEVER leave this plugged in for more than 5 seconds. This should help the problem a bit, but may temporarily make it worse. After doing this step three or four times, plug the degaussing coil back into the analogue board and use the strong magnet to spot-fix any remaining areas. If you have a second CC with working circuitry, you may wish to follow Step 2 above as an additional fix. If you can't get it thoroughly degaussed, take the tube (or whole computer) to a TV repair shop and have them professionaly degauss it.
Alternative to Step 3: buy a degaussing coil on eBay for about $10-20 and use that. It's safer and less powerful than the DIY method described above. You can also use some sort of current-limiting AC transformer to step the voltage down, which is basically how the commercial coils work.