Good evening all
Would anyone be able to supply me with a photo of the back of a 904b, ideally the selector switch and the wiring and links to the board or let me know the wiring colours
Many thanks
Looking at the schematics, it seems really simple wiring. The switch is a 2 way 4 poles rotary, and each pole is connected to each stage in the filter ladder, and it connects or disconnects additional capacitors for each stage, selecting either high or low range.
http://www.freeinfosociety.com/electronics/schemview.php?id=944
Ahhhhh so high simply breaks all the contacts of all four poles?
Not quite. It leaves only one capacitor connected to each stage. C16,18,21 and 23. But essentially, yes, it’s an on/off switch that either connects, or disconnects additional caps for each stages. It’s like four independant on/off switches into one.