The memory jumper for 70/60ns doesn't exist on a blizzard 1260. There is a jumper for enable/disable the maprom.
Do the following things to check ypur problem:
First get the b1260 and scsi-kit out your A1200 and try to start you Amiga 1200.
If this working try to insert you b1260 without memory And if this working try your old simm and then your scsi-kit.
If it fails, find a friend to test your b1260. If the last option also fails then you have to sent it for repair.
