Editing DECpc 433 General Maintenance

<templatestyles src="Template:StyledTable/styles.css" />
[[File:DECpc 433 Workstation interior (bitsavers).jpg|thumb|right|340px|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.<ref name="sg" /><ref name="trm" /><ref name="photo" />

== Before opening ==
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.<ref name="sg3c" /> Before any work that may disturb the clock battery, enter Setup and write down every setting.<ref name="sg23" />

== Opening the system box ==
DEC's procedure for the outside cover:<ref name="sg34" />
# Switch off any attached devices, then the system box.
# Label and disconnect the external cables and all power cords.
# Unlock the cover with its key.
# 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.<ref name="sg34" />

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.<ref name="sg39" />

== Clock battery ==
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.<ref name="sg23" /> 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.<ref name="sg3p" /><ref name="trma" /> 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.<ref name="photo" />

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.<ref name="sg1" /><ref name="trma" /><ref name="photo" /> 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:<ref name="sg23" />
# Record the Setup settings.
# Remove the outside cover, the inner cover and, if fitted, the 2.5-inch hard disk.
# Unplug the battery cable from header J8 and pull the battery off its Velcro pad.
# Fit the new battery to the pad, plug it into J8, and refit the disk and covers.
# Run Setup and enter the configuration again.

== Memory and cache ==
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.<ref name="sg1" /> The optional external cache module is 64 KB or 128 KB.<ref name="sg1" /> The graphics controller's four SIMM sockets take 1 MB or 4 MB SIMMs and move with the controller if it is replaced.<ref name="sg1" />

== Power supply ==
The 105 W supply powers the board and the 3.5-inch drives; the 2.5-inch disk is powered from the board.<ref name="sg1" /> It switches itself between 90–132 V and 180–264 V input.<ref name="trm11" /><ref name="sga" /> To remove it:<ref name="sg31" />
# Remove the outside cover, the inner cover and the intelligent graphics controller.
# Label and disconnect the supply's connectors from the drives and the system board.
# 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.
# 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.<ref name="sg31" /> DEC publishes no component list for the supply.

== Passwords and CMOS ==
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.<ref name="trm4" />

== Spare part numbers ==
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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
|}
<ref name="sg3p" />

== Related pages ==
* [[DECpc 433]]
* [[DECpc 433 Troubleshooting Guide]]
* [[DECpc 433 Documentation]]
* [[Floppy Drive Repair]]
* [[Recommended Tools]]

== References ==
<references>
<ref name="sg">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]]).</ref>
<ref name="sg1">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").</ref>
<ref name="sg3c">DEC, ER-PCW10-SV-001, p. 3-3. Warning and caution before beginning.</ref>
<ref name="sg3p">DEC, ER-PCW10-SV-001, pp. 3-1 to 3-2, Table 3-1. System box FRU part numbers.</ref>
<ref name="sg34">DEC, ER-PCW10-SV-001, pp. 3-4 to 3-8. Removing and replacing the outside cover; power cord safety loop.</ref>
<ref name="sg39">DEC, ER-PCW10-SV-001, pp. 3-9 to 3-12. Chassis inner cover.</ref>
<ref name="sg23">DEC, ER-PCW10-SV-001, pp. 3-23 to 3-24. System battery.</ref>
<ref name="sg31">DEC, ER-PCW10-SV-001, pp. 3-31 to 3-33. Power supply removal and replacement.</ref>
<ref name="sga">DEC, ER-PCW10-SV-001, p. A-1, Table A-1. Input ranges.</ref>
<ref name="trm">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]]).</ref>
<ref name="trm4">DEC, ER-PCW1A-TR, p. 4-19, Table 4-13. Password and CMOS jumpers.</ref>
<ref name="trm11">DEC, ER-PCW1A-TR, p. 11-1. Automatic input range sensing.</ref>
<ref name="trma">DEC, ER-PCW1A-TR, p. A-2, Table A-1. "Alkaline system battery, 3-year shelf life".</ref>
<ref name="photo">Photographs of DECpc 433 Workstation serial number 2B21100274, [http://bitsavers.org/pdf/dec/decpc/DECpc_433/sn_2B21100274/ bitsavers.org] ([[:File:DECpc 433 alkaline clock battery and corrosion (bitsavers).jpg]]).</ref>
</references>

[[Category:Digital Equipment Corporation]]
[[Category:Maintenance Guides]]