Look closely on the top of the board, everything is labeled there. Lemme see if there is a cap map for you monitor around somewhere. Nope, none to be found!
Oh, I just read this on another page which applies to K7000 monitors, and might apply to your K7400....
Got the Bends?? (Not sure what the means, but sounds like what you are seeing)
Do Not Hook Up Your Composite Sync to both H & V On this Chassis. USE H ONLY! Leave V Empty.....
So, at least for the K7000, pin 5 is a N/C and Composite Sync goes to pin 6 only.
Maybe give that a shot and see if it clears up the picture.
If you do call Wells, order a manual for the monitor too. It will have pinouts, schematics and a component layout diagram that shows where all the caps go.