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DECpc 433 General Maintenance

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Inside a DECpc 433 Workstation. The clock battery pack sits against the front panel at upper left, beside rusted chassis tabs (bitsavers.org)

Opening, battery care and routine service for the DECpc 433 Workstation, from DEC's DECpc 433 Workstation Service Guide (ER-PCW10-SV-001) and Technical Reference Manual (ER-PCW1A-TR), with photographs of a surviving machine.[1][2][3]

Before opening

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DEC's warning is to disconnect the power before opening the covers, because of the risk of electric shock, and its caution is to work at an anti-static workstation or wear a wrist strap clipped to the chassis.[4] Before any work that may disturb the clock battery, enter Setup and write down every setting.[5]

Opening the system box

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DEC's procedure for the outside cover:[6]

  1. Switch off any attached devices, then the system box.
  2. Label and disconnect the external cables and all power cords.
  3. Unlock the cover with its key.
  4. Push in the two locking tabs below the lock while lifting the cover, raise it to free the hinges, and lift it off.

To refit it, lower the side away from the tabs first to engage the hinges, make sure the power cord safety loop lies between the power supply and the rear panel, push down until the tabs click, then press above the front and rear panels to seat the detents, and lock it.[6]

Under it, a chassis inner cover is held by five screws to the intelligent graphics controller and by a locking tab; remove the screws, lift the tab and slide the cover off.[7]

Clock battery

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The configuration and clock are kept by a battery that plugs into header J8 on the system board and is stuck with Velcro to a pad inside the front panel.[5] DEC's parts list gives it as a 4.5 V battery, part 29-28951-01, and its technical reference as an alkaline battery with a three-year shelf life.[8][9] On a surviving machine the pack is a Duracell MN1500CCB "Alkaline Computer Clock Battery", 4.5 V 2.45 Ah, labelled with a warning that it may explode or leak if recharged; the chassis metal above it has rusted.[3]

DEC's sources disagree on charging. The service guide says the battery "receives charge current when power is applied", while the technical reference and the battery itself say it is alkaline.[10][9][3] The pack's own label warns that it may explode or leak if recharged. See Battery Explosion, Capacitor or Corrosion Damage for cleaning up alkaline leakage and Battery Refurbishment for building a replacement pack.

DEC's replacement procedure:[5]

  1. Record the Setup settings.
  2. Remove the outside cover, the inner cover and, if fitted, the 2.5-inch hard disk.
  3. Unplug the battery cable from header J8 and pull the battery off its Velcro pad.
  4. Fit the new battery to the pad, plug it into J8, and refit the disk and covers.
  5. Run Setup and enter the configuration again.

Memory and cache

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The system board has three banks of four SIMM sockets taking 1 MB × 9 or 4 MB × 9 SIMMs of 80 ns or faster. Sizes can differ between banks but all four SIMMs in one bank must match. The base 8 MB is eight 1 MB SIMMs.[10] The optional external cache module is 64 KB or 128 KB.[10] The graphics controller's four SIMM sockets take 1 MB or 4 MB SIMMs and move with the controller if it is replaced.[10]

Power supply

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The 105 W supply powers the board and the 3.5-inch drives; the 2.5-inch disk is powered from the board.[10] It switches itself between 90–132 V and 180–264 V input.[11][12] To remove it:[13]

  1. Remove the outside cover, the inner cover and the intelligent graphics controller.
  2. Label and disconnect the supply's connectors from the drives and the system board.
  3. Loosen the two fasteners and prise them free of the chassis with a flat screwdriver, then prise under each to release it from the supply.
  4. Tilt the supply towards the graphics controller's standoffs and lift it out.

When refitting, keep the positioning tab between the supply and the chassis and check that no cable is pinched.[13] DEC publishes no component list for the supply.

Passwords and CMOS

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To clear a forgotten password, move jumper E1 from pins 1–2 to pins 2–3; to clear the CMOS RAM, move it from pins 4–5 to pins 5–6. Return them to the default positions afterwards.[14]

Spare part numbers

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System box FRUs (from DEC Table 3-1)
Part DEC part number
System board, riser and 8 MB 29-28952-01
Intelligent graphics controller 29-28953-01
Power supply, 105 W 29-28939-01
SIMM, 1 MB × 9 29-28940-01
SIMM, 4 MB × 9 29-28941-01
Battery, 4.5 V 29-28951-01
1.44 MB 3.5-inch diskette drive RX23-AA
External cache, 64 KB / 128 KB PCWXM-AA / PCWXM-AB

[8]

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References

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  1. ↑ Digital Equipment Corporation, DECpc 433 Workstation Service Guide, ER-PCW10-SV-001, June 1991 (File:DECpc 433 Workstation Service Guide (ER-PCW10-SV-001).pdf).
  2. ↑ Digital Equipment Corporation, DECpc 433 Workstation Technical Reference Manual, ER-PCW1A-TR, December 1991 (File:DECpc 433 Workstation Technical Reference Manual (ER-PCW1A-TR).pdf).
  3. ↑ 3.0 3.1 3.2 Photographs of DECpc 433 Workstation serial number 2B21100274, bitsavers.org (File:DECpc 433 alkaline clock battery and corrosion (bitsavers).jpg).
  4. ↑ DEC, ER-PCW10-SV-001, p. 3-3. Warning and caution before beginning.
  5. ↑ 5.0 5.1 5.2 DEC, ER-PCW10-SV-001, pp. 3-23 to 3-24. System battery.
  6. ↑ 6.0 6.1 DEC, ER-PCW10-SV-001, pp. 3-4 to 3-8. Removing and replacing the outside cover; power cord safety loop.
  7. ↑ DEC, ER-PCW10-SV-001, pp. 3-9 to 3-12. Chassis inner cover.
  8. ↑ 8.0 8.1 DEC, ER-PCW10-SV-001, pp. 3-1 to 3-2, Table 3-1. System box FRU part numbers.
  9. ↑ 9.0 9.1 DEC, ER-PCW1A-TR, p. A-2, Table A-1. "Alkaline system battery, 3-year shelf life".
  10. ↑ 10.0 10.1 10.2 10.3 10.4 DEC, ER-PCW10-SV-001, pp. 1-3 to 1-5. SIMMs, external cache, power supply, drives, graphics controller, battery ("receives charge current when power is applied").
  11. ↑ DEC, ER-PCW1A-TR, p. 11-1. Automatic input range sensing.
  12. ↑ DEC, ER-PCW10-SV-001, p. A-1, Table A-1. Input ranges.
  13. ↑ 13.0 13.1 DEC, ER-PCW10-SV-001, pp. 3-31 to 3-33. Power supply removal and replacement.
  14. ↑ DEC, ER-PCW1A-TR, p. 4-19, Table 4-13. Password and CMOS jumpers.
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