On my ASR-33 Looks like it may be a bad transistor in the receive
circuit....
Basis for conclusion:
1) switching keyboard units has no effect.
2) disconnecting reader unit has no effect
3) R7 on receive control bord is HOT (to the touch)
4) Selector magnet appears always engaged.
5) Unit does NOT space-out when put in line mode.
Now to just find a source for the proper replacement transistors.......
David