U1 pins 2 through U2 pins 2 through U3 pins 5 through

To test the expansion frame interface

3Remove the probe ground from the frame, and reattach the probe ground to the metal portion of the expansion frame near the front panel.

4Probe the following pins.

•U1 pins 2 through 9

If all of the signal lines show TTL activity, then go to the next step.

If one or more of the signal lines do not show TTL activity, then replace the expansion frame interface board.

5With the oscilloscope probe still grounded to the frame, probe the following pins.

•U1 pins 11 through 18

•U2 pins 11 through 18

•U3 pins 11 through 15

If one or more of the signal lines do not show TTL activity, then replace the expansion frame interface board.

Bottom Side of Expansion Interface Card

5–31