10 Troubleshooting and Testing
Table 2–1 (Cont.) Troubleshooting the VT420
Symptom Probable Cause Solution
Other Problems
After power-
up, one or more
keyboard LEDs
stay on. Or,
the LEDs do
not go through
their power-up
sequence.
Keyboard.
Terminal board.
Replace the keyboard (3.4).
Replace the terminal board (3.3).
The set-up cursor
does not appear.
Terminal board. Replace the terminal board (3.3).
When using a
modem, the
modem speed
select signals do
not work.
Cables.
Terminal board.
Check all cables and cable
connections. Replace the terminal
board (3.3).
Worldwide
model: In PC
TERM mode, a
modem does not
work with the
terminal.
The modem’s XON
/XOFF settings
are incompatible
with the terminal.
Use a modem with compatible XON
/XOFF settings. In PC TERM mode,
the terminal’s XON point is 65
16
characters, and the XOFF point is
67
16
characters.
Section numbers follow the solution.
2.2 VT420 Self-Tests
The VT420 has a series of self-tests to determine if the terminal board
is the faulty field replaceable unit (FRU). You can run each test from the
keyboard by entering the escape sequence for the test. Table 2–2 lists the
tests and their escape sequences.
If a test indicates the terminal board is faulty, refer to
• Chapter 4, to adjust the components on the board, or
• Chapter 3, to replace the board
After making adjustments or replacing the terminal board, repeat the
tests in this chapter to ensure the terminal operates correctly.
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