Cure:

The horizontal frequency has drifted off from center. Locate the horizontal hold control on the vertical pc card on the right hand side of the chassis. It is the white knob on the bottom under the long protruding black knob (V. hold). Set it to it's mechanical center & leave it.

In the center of this same vertically mounted pc card, you will see a shiny metal square can about 1 inch down from the top. Looking into it you will see a red screwdriver slot. You'll need a 12" plastic screwdriver to feed through the hole on the metal chassis frame, that lines up with this screw slot in the can & adjust it until the picture straightens up. If you go the wrong way and the picture goes out altogether, don't worry, just go back in the opposite direction for a few turns & turn the monitor off for a minute & then back on. This resets your auto-shutdown circuit. Now you can continue going in the right direction until the picture is upright.

This should solve your problem & if you use your cabinet as a multi-game cab, you should try several of your pcbs in the game & adjust the small white horizontal knob to a position where any of the pcbs will plug n play.

If you still are having trouble with sync circuits, some V/H bds require a jumper across C315 eliminating it from the circuit when used with certain game pcbs, while others need C315 in circuit. There is usually a bare wire jumper on the solder side of C315 that can be cut open or tacked together as needed.

Another quirk that is often overlooked is the cap at position C614 on the main board. This cap bridges the pincusion xformer and when it grows weak it causes the picture to appear trapezoidal, or what techs call "hourglass" or "keystone". The center of the pic can bow inward )( or outward ( ), hence the 2 terms. The reason it is overlooked so much, is that in their infinite wisdom of design, they chose to mount this under the V/H card between the 2 connectors, forcing the radial cap to be mounted with extra long leads & then bent to a laying out-of-the-way position on the main board to allow the V/H card to plug in.

If you encounter the treble image or double image when changing out a monitor other than the 4600, your chances are very good that you have a medium resolution monitor rather than a standard resolution monitor, as the 4600 is the only CGA that I've seen capable of going that far off frequency to exhibit that symptom prior to shutdown.