Look at the WG6100 Quadrascan Monitor Manual Figure 15. The case transitors are shown in the drawing. Q706, Q705, Q102, Q103, Q606 and Q605. Using a meter on tone mode touch one lead to trasistor cap or mounting screw and the other lead to frame of the monitor, if the cap is not mounted correctly you will get a tone. Reposition the cap and check your screws, you should not get any tone when they are mounted correctly.
Another option would be to check for cold solderer points at the transitors on the main deflection board, P314, look for Q704, Q703, Q604 and Q603. They are attatched to heat sinks. Slightly touch each heat sink to see if there is any movement of the transitor legs, loose or cold solder joints will cause your screen to collaps either horizontally or vertically. See Figure 16 in the monitor manual for the transitor locations.