H724 (and M8320) schematics are here: http://bitsavers.org/pdf/dec/pdp8/pdp8e/PDP-8E_Engineering_Drawings_RevAD_Dec72.pdf You have the maintenance manuals too, right? http://bitsavers.org/pdf/dec/pdp8/pdp8e/DEC-8E-HMM1A-D-D_PDP-8e_Maintenance_Manual_Volume_1_Processor_Sep73.pdf Kyle