I just recently modified my Color Classic to have 640x480 resolution, and was having some problems. I noticed after the modification, when the computer is powered on, the flyback transformer seems to be making a buzzing sound. At the same time, the picture sometimes has an almost interlaced look to it (except the screen actually is distorted (it looks like each even horizontal line of pixels are positioned the same, and the odd lines are positioned 1/4" to the left or right of the even lines)).
After trying to adjust the screen, the 'interlaced' (sorry, can't describe it any other way) distortion seems a little more minimized. (just lowering the horizontal width as much as possible)
I do have pretty bad barrel distortion as well. Everything with the modification seemed to go fine, however, it seems like I must've done something wrong. I have read about adding a capacitor to reduce the barrel distortion. Could that possibly fix the other problem as well though?