My Yashica GSN seems to work well with all shutter speeds and f stops behaving as they should but I cannot get either lamps to light for the "slow/over". I did see them flicker once when I got the camera for a second but that was it. Any help would be great thanks.
Sometimes it is the latch which keeps the lower part of the shutter release shaft in the down position. Remove the bottom cover. There should be a tiny latch lever which fits into a cutout on a shaft. When turning the advance crank this latch should be released and the shutter shaft should pop upwards.
It may be a broken lamp(s) or open contact(s). Often we find corroded wire in the old YASHICA too.
Your GSN works well for shutter control. So the electronic circuit is good. Because the shutter control and lamp switching functions use same transistor on the circuit.
Please refer to Roger Provins' nice page. http://www.provins.org.uk/ "Yashica Electro 35 meter schematics"
The FIG.62 and FIG.63 show current pass for those lamps.
