The schematics available for Atari SM124 differ a little from the actual boards described below. Some of the capacitors have different symbols and some parts are interconnected in a different way.
C716 bipolar capacitor (C714 on schematics, rated 2.2uF 50V) is a single part most likely to fail. It is part of a horizontal deflection circuit and its failure results in a single vertical line on the screen. It has to be replaced with a part suitable for high impulses, for example a polypropylene MKP capacitor. Replacing it with a regular electrolytic capacitor of the same ratings will result in a blowup of that capacitor.
The difference in this revision is a different design of the right-bottom part, where in revision 1.0 there are some cables and resistors soldered. Also, instead of transistors, an integrated operational amplifier is used.
In this revision resistor R617 is added and a position of R614 was changed.