Remove diodes D71 through 74. The new diodes are packaged in matched pairs. Use one pair to replace D71 and D72. Use the second pair for D73 and D74. Caution must be used when soldering in the new diodes. The diodes can be damaged by heat. The leads should be fashioned in the way the manual recommends. (A free copy can be provided if you don’t already have one) Each lead should be heat-sinked using the Radio Shack Soldering Heat Sink Clip Tool (part # 276-1567) or similar.