IBM 3270 Maintenance Manual page 72

Check the 9-pin keyboard connector at the
system unit for the appropriate voltages, as
shown below.
(Back of
System Unit)
- - - 1
Pin
1
2
3
4
5
6
7
8
9
2
3
4
5
Voltage
2.0 - 5.5 Vdc
o
-.L9Vdc
No Connection
2.0 - 5.5 Vdc
2.0 - 5.5 Vdc
4.5 - 5.5 Vdc
No Connection
Ground
Ground
ARE THE VOLTAGES CORRECT?
NO
Replace the keyboard/timer adapter. See
Section 5, "Removal/Replacement and
Adjustments. "
YES
October 1984 3-20-3