This is for attempting to read 17777170-6? (One needs the exact details, always! ;-) If so, either i) the RX211 card is set for some other address (check its address switch at E74; switch 1 {pins 1-20] is the 010 bit in the address, on up to 010000 at switch 10), ii) the RX211 card is defective, or the KTJ11 is defective. Since you don't have any known good devices plugged into the UNIBUS, it's hard to select among these possibilities. Do you have any other UNIBUS devices (other than the Tk controller) you can plug in? Also, just for grins, you could try reading addresses 17777730-34, which are registers on the KTJ11 itself, and see what you get. Noel