I have access to a real MiG-21 equipment, so I will leave few comments here:
ASP gunsight controls are bad. See attached picture
1) sets the aim rectile size. The lower the number on the deal the smaller the rectile is.
2) sets the aim rectile angle. If it's on 0, the rectile is in midle of the fixed net. The higher number set, the lower the rectile goes.
3) sets the backlight intensity of elements 8 and 9
4) sets the intensity of the aim rectile
5-6) there are 2 lamps in the ASP, one for aim rectile, the other for the fixed net. Each of this lamp have two filaments. If one fails, you use this switches to use the other filament. Num 5 is for fixed net, num 6 is for aim rectile. When switch, the rectile fades out and back in as the filament changes.
7) sets the fixed net brightness, left turn makes it less bright
SPO indicator only have 4 lamps inside. Even though it looks there are 8, but this is to mechanically switch between day and night intensity of the lamps. So each second "hole" in the cover have smoked glass and thats for the lower intensity. If you rotate the cover of the SPO indicator left-right, you are changing the filer through which the light is emmited, but still there are only 4 lamps inside. (Or 5, the fifth is for the ZVUKA NET symbol).
It works the way that if the RWR signal comes from +/- 22.5° both top lamps shine. If the signal comes from 22.5 - 67.5 only the top right lamp shines. If the signal comes from 67.5-112.5 both right lamps are shining etc all around.