Marantz 2220B serial number #U353553 One more for the 2220B. This time on P800 power board. The board diagram and parts list in the service manual show H803 as DS-131B and H804 as DS-132B dual diodes. These positions should actually be reversed, as H803 is DS-132B and H804 is DS-131B. This is also confirmed in the schematic which doesn't list the part numbers but does show the proper positions for these common cathode and common anode dual diodes.