A couple of notes. On 9090 the newer driver boards will work in older units but not vice versa. The older units without the fuses on driver board had a jumper on board connected the fuse replaces that jumper so and older board will not work in newer chassis without the jumper being added. I believe the cadmium plated chassis was added mid year 1977, might be wrong I have to see what I have. The fuses replacing the fuse resistors were added to make the units shipped directly to US, UL approved. Most multi voltage units were built for the US Military with some for Europe. Single voltage units were built exclusively for NZ/AU, GB, which did not have outlets in rear of the unit. Yes those printed circuit “cables” between switch board and Dolby were a nightmare. Some of the really early driver boards used in 9090 had the suppressor coils mounted on driver board but these may have only been used in other Sansui amps same vintage. I have found that the printed board for the 8080/9090 is much more subject to soldering damage the most other PC boards. Pete unless I am doing a complete restoration, I only fix Dolby board feed thrus that are defective.