I am looking to replace a blown Zener diode for a Morrow s-100 mother board called Wuderbuss with Noise Guard 1977 G. Morrow Thinker Toys. Any known schematics? Here is the problem: http://vintagecomputer.net/Morrow/wuderbuss_mb_s-100.jpg ...note the blown Zener Diode at the top of the picture. I am unsure of the cause. Thanks. Bill