9 Maintenance and Troubleshooting

General

This chapter describes maintenance procedures, troubleshooting (what to do in the event of a problem), and self-tests used with the VT102. You should troubleshoot the terminal before requesting service.

Maintenance

The terminal does not need preventive maintenance. However, you can clean terminal and screen surfaces with any mild detergent that does not use solvents; apply the detergent with a cloth or tissue. To clean the keys, rub with a dry or moist cloth.

CAUTION: Do not use too much detergent when cleaning the terminal. Liquids can damage the inside of the terminal. Do not remove the keycaps when cleaning; you can damage the keyswitch contacts by replacing the keycaps incorrectly.

Troubleshooting

If you suspect a problem with the terminal, check Table 9-1 to see if the symptoms are there. If the problem is not listed in Table 9-1, use the following procedure:

  1. Turn the power switch off (0) (Figure 9-1).
  2. Check the following items.

    Voltage selection switch and fuse. Make sure the switch is in the correct position. Select 120 volts by performing the following procedure.

    1. Set the voltage selection switch to 115 (operating voltage range 99 to 128 Vac). On some terminals, the setting is 100 (operating range 87-107 Vac).
    2. Remove the fuse holder cap by pressing in and turning counter-clockwise. Check for a 1.25 A fuse (DIGITAL PN 90-0020-01) and make sure the wire in the fuse is not broken.

    Select 220-240 volts by performing the following procedure.

    1. Set the voltage selection switch to 230 (operating voltage range 198 to 256 Vac). On some terminals, the setting is 250 (operating range 222-268 Vac).
    2. Remove the fuse holder cap by pressing in and turning counter-clockwise. Check for a 0.75 A slow blow fuse (DIGITAL PN 12-11237-00) and make sure the wire in the fuse is not broken.

    Power cord. Make sure the cord is connected securely at both the terminal and the wall outlet. Check ac power at the wall outlet with another device such as a lamp.

    Keyboard coiled cord. Make sure the cord is securely plugged into the keyboard connector at the back of the terminal.

  3. Perform all the tests in the following section.
Table 9-1   Problem Checklist
Symptom Possible Cause Corrective Action
ON LINE or OFF LINE is on with no cursor on screen. Screen brightness too low. Enter SET-UP and increase screen brightness.
ON LINE and OFF LINE are not on with no keyboard response. Cursor on screen. Keyboard cable not connected to terminal. Connect keyboard cable.
KBD LOCKED is on. Characters are typed faster than terminal can transmit them. Cleared when terminal transmits characters in keyboard character buffer to computer.
Locked condition occurs when terminal is receiving characters with half-duplex communication selected (by modem control SET-UP feature). Terminal cannot transmit characters when receiving characters in half-duplex. Cleared when line turns around and terminal can transmit keyboard characters.
Print operation selected while off-line. Cleared when print operation ends.
Terminal not connected to computer correctly. Communication line signals are not correct. Cleared when correct connection exists between computer and terminal.
Terminal does respond to typed characters. Computer cannot update screen. Press NO SCROLL.
Computer turns keyboard off. Computer turns keyboard on.
Garbled or error ([]) characters or no characters appearing on screen. Incorrect SET-UP feature selected. Correct SET-UP features.
Computer error occurred. Check computer system.
Two characters appear on screen for each character typed. Local echo on. Turn local echo off.
Several bell tones during power up, reset or recall. Read or write problem with user permanent memory. Check SET-UP feature settings and try save operation.
Printer does not print characters. Printer and terminal features do not match. Check SET-UP feature settings of terminal and printer.
Figure 9-1 Monitor Controls

Self-Tests

The terminal uses self-tests to verify operation. The self-tests provided are a power-up self-test, three loopback self-tests, and a printer test. The power-up self-test runs each time the terminal is powered up. The loopback self-tests may run after the power-up self-test ends; these self-tests need an optional loopback test connector. The printer test ensures that the terminal and printer can communicate.

Power-Up Self Test

A power-up self-test runs each time you turn the power on (power up). The test checks general terminal operation, user memory (holding SET-UP features), and the keyboard. Perform the power-up self-test by using the following procedure.

  1. Start the power-up self-test in one of the following ways.

    The single test ends with the following indications.

    The continuous test also displays test data, the wait message, then erases screen. This test ends only if it finds an error or power is turned off.

    When the power-up self-test finds an error, the terminal provides one of the following indications.

    There are two failures that allow the terminal operation to continue: a user memory failure indicated by a 2 on the screen and several bell tones, and a keyboard failure indicated by a 4 on the screen. The user memory failure allows continued operation after you select SET-UP features in operating memory. The keyboard failure allows the terminal to continue to operate as a receive-only terminal.

  2. After a single test, enter SET-UP to verify a successful test. A SET-UP A display should appear on the screen. If not, call your local DIGITAL Field Service Office.

Data Loopback Self-Test

The data loopback self-test verifies that the terminal can transmit and receive characters. You must connect the transmit and receive lines to each other with the EIA loopback connector (DIGITAL PN 12-15336) available from the DIGITAL Accessories and Supplies Group (Chapter 10). The terminal transmits characters on the transmit line and receives the characters on the receive line. Perform the data loopback self-test by using the following procedure.

NOTE: See Chapter 8 to perform the data loopback self-test with the 20 mA current loop option (VT1XX-CA) installed.

  1. Turn the power switch off (0).
  2. Unplug the communication cable and install the EIA loopback connector on the modem connector (Figure 9-2).
  3. The internal communication switch S6 must be on (closed) to perform this test. If the switch is off (open), remove the access cover, turn the switch on (closed), and install the access cover. See Internal Communication Switch Selection in Chapter 7 for details.

    NOTE: Usually, this switch is only open when you set the modem control SET-UP feature for asymmetric full-duplex (FDX C).

  4. Turn the power switch on (1). The terminal performs the power-up self-test.
  5. Type one of the following sequences to perform the data loopback self-test. The terminal must be off-line with the ANSI/VT52 SET-UP feature set to ANSI (SET-UP B switch 2-3 = 1).
    ESC [ 2 ; 2 y Performs the self-test once.
    ESC [ 2 ; 10 y Performs the self-test continuously.

    The single test displays the wait message while running. The single test ends with the following indications.

    The continuous test displays the wait message while running. The test ends only if it finds an error or power is turned off.

    When the test finds an error, the terminal displays an error character. Call your local DIGITAL Field Service office for assistance.

  6. If the test runs successfully, turn the power switch off and remove the loopback connector. If you set switch S6 to run this test, change the switch to its original position.
  7. Connect the communication cable.
Figure 9-2 EIA Loopback Connector (Modem)

EIA Loopback Self-Test

The EIA loopback self-test verifies that the terminal can operate its modem control lines. Perform the EIA loopback self-test by using the following procedure.

  1. Turn the power switch off (0).
  2. Unplug the communication cable and install the EIA loopback connector on the modem connector (Figure 9-2). The EIA loopback connecotr (DIGITAL PN 12-15336) is available from the DIGITAL A&SG (Chapter 10).
  3. The internal communication switches S1, S2, S4, S6, S8, and S9 must be on (closed) to perform this test. If any of these switches are off (open), remove the access cover, turn the switches on (closed), and install the access cover. See Internal Communication Switch Selection in Chapter 7 for details.
  4. Turn the power switch on (1). The terminal performs the power-up self-test.
  5. Type one of the following sequences to perform the EIA loopback self-test. The terminal must be off-line with the ANSI/VT52 SET-UP feature set to ANSI (SET-UP B switch 2-3 = 1).
    ESC [ 2 ; 4 y Performs the self-test once.
    ESC [ 2 ; 12 y Performs the self-test continuously.

    The single test displays the wait message while running. The test ends with the following indications.

    The continuous test displays the wait message while running. The test ends only if it finds an error or power is turned off.

    When the test finds an error, the terminal displays an error character. Call your DIGITAL Field Service office for assistance.

  6. If the test runs successfully, turn the power switch off and remove the loopback connector. If you set switches S1, S2, S4, S6, S8 or S9 to run the test, change the switches to their original position.
  7. Connect the communication cable.

Printer Loopback Self-Test

The printer loopback self-test verifies that the terminal's printer interface can transmit and receive characters. In this test, you connect the transmit and receive lines with the EIA loopback connector. The terminal transmits characters on the transmit line and receives the characters on the receive line. Perform the printer loopback self-test by using the following procedure.

  1. Turn the power switch off (0).
  2. Unplug the printer cable and install the EIA loopback connector on the printer interface connector (Figure 9-3). The EIA loopback connector (DIGITAL PN 12-15336) is available from A&SG.
  3. Turn the power switch on (1). The terminal performs the power-up self-test.
  4. Type one of the following sequences to perform the printer loopback self-test. The terminal is off-line with the ANSI/VT52 SET-UP B feature set to ANSI (SET-UP B switch 2-3 = 1).
    ESC [ 2 ; 16 y Performs the self-test once.
    ESC [ 2 ; 24 y Performs the self-test continuously.

    The single test displays the wait message while running. The test provides the following indications.

    The continuous test displays the wait message while running. The test ends only if it finds an error or power is turned off.

    When the test finds an error, the terminal displays an error character. This indicates a printer interface failure. Call your local DIGITAL Field Service office for assistance.

  5. Turn the power switch off (0) and remove the loopback connector.
  6. Connect the printer cable.
Figure 9-3 EIA Loopback Connector (Printer)

Printer Test

The printer test verifies that the terminal and printer can communicate. This test generates sample data for printing and transmits that data to the printer. Perform the printer test by using the following procedure.

  1. Connect the printer cable to the printer and the terminal's printer connector. Turn both the terminal and printer on.
  2. Make sure the following terminal and printer features match.
  3. Type the following sequence on the keyboard. The terminal must be off-line with the ANSI/VT52 SET-UP feature set to ANSI (SET-UP B switch 2-3 = 1).
    ESC # 8 The screen fills with E's.
  4. Hold down SHIFT and press (PRINT); the E's should print. If the E's do not print, call your local DIGITAL Field Service Office.