IBM 3270 Maintenance Manual page 64

Running POST
1. Set the Power switch for the system unit (and
expansion unit, if attached) to Off
(0).
2.
If your display has an On/Off (I/O) switch,
make sure that it is set to On (I).
3.
If your display has brightness or contrast
controls, make sure that they are turned fully
clockwise.
4.
If you have an expansion unit attached, set
the Power switch to On (I).
Note: If you have an expansion unit, you
must
tur~
it on before.the system unit or you
may receIve error messages.
5. Set the Power switch for the system unit to
On
(I)
and watch and listen for the three
correct responses.
Note: Pressing a key during POST may be
interpreted, by the test, as an error. Make sure
that no keys are pressed while this test is
running.
DID ALL THREE CORRECT RESPONSES
OCCUR?
YES Go to "Diagnostic Testing
90" on
page
3-90-1.
NO
Go to "POST Error Chart
15" on
page
3-15-1.
October
1984 3-10-3