IBM 5150 Hardware Maintenance Manual page 51

Position the System Unit Power switch to Off, remove the
keyboard connector at the System Unit, then power on. Check
the keyboard connector at the System Unit for the appropriate
voltages, as shown in the diagram.
(Rear View of System Unit)
5
o
2
o
Pin
,~
1
2.0 - 5.5 Vdc
2
2.0 - 5.5 Vdc
3
2.0 - 5.5 Vdc
4
Ground
5 2.0 - 5.5 Vdc
ARE ALL THE VOLTAGES CORRECT?
NO
Replace the System Board. See Section 3,
"Removal/Replacement. "
YES
Check keyboard cable connectors for damage,
then replace keyboard assembly. See Section 3,
"Removal/Replacement. "
300-2