IBM 5155 Manual To Operations page 169

Test 8020
1
Check your wall outlet for proper operation (use
a working lamp).
2
Verify that your printer cable is properly
connected to the printer and the system unit.
Did you find any problem while doing the above
step?
NO - Go to the next step.
YES -
Correct the problem and perform the
system diagnostic tests again.
3
Set the Power switches on the printer and
system unit to Off.
(If
an expansion unit is
attached, also set its Power switch to Off.)
4
Disconnect the printer cable.
January
1984 Test 8020-1