DECmate I General Maintenance
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Care and routine checks for the DECmate I (VT278), taken from DEC's DECmate Owner's Guide, DECmate Technical Description and DECmate System Architecture Manual.[1][2][3] The VT278 is a VT100-style terminal with a CRT and a mains switching power supply; read CRT Discharge Procedure before opening it.
Site and power
[edit | edit source]DEC's owner's guide sets these conditions for a DECmate system.[1][4]
| Condition | Maximum range | Recommended |
|---|---|---|
| Temperature | 15–32 °C (59–90 °F) | 18–24 °C (65–75 °F) |
| Relative humidity | 20–80% | 40–60% |
| Altitude | 2.4 km (8,000 ft) maximum | |
| Clearance | 15 cm (6 in) on all sides for maintenance and airflow to the fans | |
In North America DEC specifies a 120 V, 3-wire, grounded 15 A supply, with each DECmate on its own circuit breaker and nothing else, such as copiers or coffee pots, on that circuit. The guide gives 3.1 A at 120 V (315 W) for the minimum configuration and 8.6 A (985 W) for the maximum, which includes drives and printers.[4]
Voltage and frequency selection
[edit | edit source]The VT278 power supply accepts 120 V or 220/240 V, chosen by a slide switch on the rear panel; a second switch selects 50 Hz or 60 Hz.[2] DEC's installation steps require 120 V/60 Hz in North America and 220–240 V/50 Hz in Europe, and tell the installer to check the yellow label on the power socket before connecting.[5] Check both switches whenever a machine has changed hands or countries. The main fuse is on the same panel.[6]
Display and keyboard
[edit | edit source]The video monitor board holds all the video adjustment controls.[2] Brightness is set from the keyboard: enter SET-UP and use the up and down cursor keys, which step through 16 levels. The VT278 starts at the mid-point after power-on.[7]
The keyboard is powered from the terminal: two wires of its 3-wire cable carry +12 V and ground, and the third is the serial data line.[2] A keyboard that does not answer stops the self-test at test T3, so check the cable and its connector first when a machine stops with CPU OK lit continuously.[3]
Routine checks
[edit | edit source]- Before powering up a machine that has been stored, check the selector switches and the fuse, and inspect the monitor board for leaking electrolytics.
- Switch on and watch the self-test. PWR OK on the rear panel should light, CPU OK should blink once a second, and SET-UP should appear on the screen with only ON LINE lit on the keyboard.[3]
- Run the self-test again from SET-UP by pressing 0.[8]
- Use LOCAL mode (SET-UP, then 9) to test the keyboard and display by typing directly to the screen.[8]
- Boot the System Test diskette from drive 0 (SET-UP, then 2) to test the diskette system.[9]
Capacitors
[edit | edit source]The aluminium electrolytics are on the monitor board, the keyboard and the DP278 communications option. The CPU and I/O connector boards use solid tantalums. The full list with DEC part numbers is on DECmate I Capacitor Replacement Guide.
Diskette drives
[edit | edit source]The DECmate I uses RX02 8-inch dual drives in a separate unit, connected through a 37-pin connector at the rear of the VT278.[2] Each diskette holds 256,256 12-bit words on 77 tracks.[10] See Floppy Drive Repair for drive cleaning and alignment.
Related pages
[edit | edit source]- DECmate I
- DECmate I Troubleshooting Guide
- DECmate I Capacitor Replacement Guide
- DECmate I Documentation
- CRT Discharge Procedure
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 Digital Equipment Corporation, DECmate Owner's Guide, AA-K330E-TA, July 1982, p. 9-2 (File:DECmate Owner's Guide (AA-K330E-TA).pdf). Temperature, humidity and altitude.
- ↑ 2.0 2.1 2.2 2.3 2.4 Digital Equipment Corporation, DECmate Technical Description, EK-VT278-TD-001, March 1981, pp. 1-3 to 1-4 (File:DECmate Technical Description (EK-VT278-TD-001).pdf). Keyboard cable, power supply input switches, video monitor, diskette connector.
- ↑ 3.0 3.1 3.2 DEC, DECmate System Architecture Manual, EK-VT278-HR-001, pp. 3-4 to 3-5. LED indicators and self-test.
- ↑ 4.0 4.1 DEC, DECmate Owner's Guide, AA-K330E-TA, p. 9-3. Clearance, line voltage and service, power for minimum and maximum configurations.
- ↑ DEC, DECmate Owner's Guide, AA-K330E-TA, pp. 1-18 and 4-19. Yellow voltage label and Voltage Select/Frequency Select switches.
- ↑ DEC, DECmate System Architecture Manual, EK-VT278-HR-001, p. 3-3, Figure 3-2. Rear panel.
- ↑ DEC, DECmate System Architecture Manual, EK-VT278-HR-001, p. 3-6, section 3.4.1. Screen brightness.
- ↑ 8.0 8.1 DEC, DECmate System Architecture Manual, EK-VT278-HR-001, p. 3-7, sections 3.4.2 and 3.4.3. Repeat self-tests; LOCAL mode.
- ↑ DEC, DECmate Owner's Guide, AA-K330E-TA, pp. 5-14 to 5-15, "Solving Problems". System Test diskette in drive 0.
- ↑ Digital Equipment Corporation, DECmate System Architecture Manual, EK-VT278-HR-001, June 1981, pp. 1-4 to 1-6 (File:DECmate System Architecture Manual (EK-VT278-HR-001).pdf). RX02 capacity.