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DECmate II General Maintenance

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DECmate II with VR201 monitor and LK201 keyboard (Centre for Computing History)

Care, routine checks and module handling for the DECmate II, based on DEC's DECmate II Owner's Manual (EK-DECM2-OM-001) and print set (MP-01492-00).[1][2] The VR201 monitor contains a CRT and the system unit contains a mains switching supply: read CRT Discharge Procedure before opening the monitor.

Site and environment

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DECmate II operating environment (DEC)
Condition Value
Temperature 15–32 °C (59–90 °F)
Relative humidity 20–80% (DEC recommends 40–60%)
Maximum wet bulb 25 °C (77 °F)
Minimum dew point 2 °C (36 °F)
Clearance About 15 cm (6 in) round the system unit and monitor

[1][3]

DEC's other placement advice: keep the unit away from heat registers, air conditioners and large windows; do not share its mains circuit with copiers, typewriters or other motor-driven machines; and keep the air clean, because dust clogs the air passages and reduces the fan's cooling.[1] The monitor cable is 2 m (6 ft) long, which limits how far the monitor can be from the system unit.[1]

Cleaning

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DEC's cleaning instructions:[4]

  • Switch the power off before cleaning any surface.
  • Clean the outside with a little soap or mild detergent on a damp cloth. Never use a spray or a cleaning solvent, and do not let liquid run into the vents.
  • Clean the monitor screen with a cloth moistened with alcohol or water, not a spray cleaner.
  • Leave the keycaps in place when cleaning the keyboard; removing them can damage the switch contacts.
  • Never move the system unit while it is running.

Power

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The voltage selection switch on the back must match the mains: 115 V or 230 V. With 230 V applied and the switch at 115 V, the circuit breaker beside the power cord trips.[5] On the Rainbow 100, which uses the same H7842 supply, DEC warns that this mistake damages internal components.[6] Check the switch on any machine of unknown history before plugging it in.

The supply's outputs and their tolerances are given on DECmate II Power Supply Service.

Removing the modules

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The system unit cover comes off by releasing latches beneath the overhanging areas on each side.[7] The four modules then come out as follows.[8][9]

  1. RX50 drive: press the tab at the front of the system unit and pull the drive forward along its tracks.
  2. Power supply: unplug the two cables from the power switch and fan assembly and the 13-pin flat cable from the system board, then move the slide tab at the end of the supply.
  3. System board: release it and slide it straight out. It lies flat along the bottom of the unit and carries any option boards on standoffs.

DEC's manual says the power switch and fan assembly should be removed only by DEC service staff because of the high voltages in it.[10] It carries mains wiring from the supply to the front switch, so unplug the machine before touching it.

Capacitors

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The DECmate II system board (54-15426) has one non-ceramic bulk capacitor, C5, a 22 µF 6 V solid tantalum. The rest are ceramic and mica.[11] The aluminium electrolytics in a DECmate II system are in the H7842 power supply and the VR201 monitor. See DECmate II Power Supply Service for the supply and DECmate III Capacitor Replacement Guide for the VR201, which the DECmate III shares.

Diskettes and the RX50

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DEC's handling rules for RX50 diskettes: keep them flat, do not clean them, keep them away from heat, sunlight, the monitor and magnets, let a cold diskette warm for 15 minutes before use, and store them flat in their envelopes in stacks of ten or fewer.[12] For the drive itself see Floppy Drive Repair.

Routine checks

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  1. Check the voltage selection switch and the circuit breaker.
  2. Inspect the H7842 for bulging or leaking electrolytics before the first power-up of a stored machine.
  3. Switch on and read the self-test result. A clean start shows the self-test message for no problems; any number is an error code, listed on DECmate II Troubleshooting Guide.[13]
  4. Run the System Test diskette to check the system board, RX50 drive and printer interface.[14]
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References

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  1. ↑ 1.0 1.1 1.2 1.3 DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, pp. 27 to 29. Location, furniture, electrical power, temperature, humidity, air quality.
  2. ↑ Digital Equipment Corporation, PC278 DECmate II print set, MP-01492-00 (File:DECmate II PC278 Print Set (MP01492-00).pdf).
  3. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, p. 96. Environment specification.
  4. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, pp. 29 to 30. Caring for the DECmate II.
  5. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, p. 4. Circuit breaker and voltage selection switch.
  6. ↑ Digital Equipment Corporation, Rainbow 100 Technical Manual, EK-PC100-TM-001, May 1984, p. 7-1, bitsavers.org. AC selector switch warning for the H7842.
  7. ↑ Digital Equipment Corporation, DECmate II Owner's Manual, EK-DECM2-OM-001, December 1982, p. 2 (File:DECmate II Owner's Manual (EK-DECM2-OM-001).pdf). System unit cover latches.
  8. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, pp. 9 to 11. System board.
  9. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, pp. 12 to 14. Power supply and RX50 drive removal.
  10. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, p. 15. Power switch and fan assembly warning.
  11. ↑ DEC, print set MP-01492-00, system board 54-15426 parts list, sheet A1 (PDF pp. 9 and 40). C5, 22 µF 6 V 10% solid tantalum.
  12. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, pp. 60 to 61. Handling diskettes.
  13. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, pp. 75 to 78. Self-test messages and error codes.
  14. ↑ DEC, DECmate II Owner's Manual, EK-DECM2-OM-001, p. 82. System test diskette.
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