Editing MicroVAX II Maintenance Guide

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[[File:DEC KA630-AA MicroVAX II CPU module M7606.jpg|thumb|right|360px|KA630-AA CPU module (M7606), which always goes in backplane slot 1 (Phiarc, CC BY-SA 4.0)]]
Routine care of a '''[[MicroVAX II]]''' covers its environment, the configuration rules for the Q22-bus backplane, the power budget, the fans, the time-of-year clock battery and DEC's MicroVAX Maintenance System (MMS) diagnostics. The procedures come from DEC's ''MicroVAX II Maintenance Guide'' (AZ-GM3AA-MN), the owner's manual and the ''KA630-AA CPU Module User's Guide''.<ref name="mg" /><ref name="om" /><ref name="ka" /> Supply work is on [[MicroVAX II Power Supply Guide]] and fault finding on [[MicroVAX II Troubleshooting Guide]].

== Environment ==
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+ '''MicroVAX II 630QB environmental limits (owner's manual, appendix B)'''
! !! Operating !! Non-operating
|-
| Temperature || 10–40 °C || −40 to 66 °C
|-
| Temperature change || 11 °C per hour || –
|-
| Relative humidity || 20–80% || 10–95%
|-
| Altitude || 2.4 km || 4.9 km
|}
<ref name="omb" />
Reduce the maximum operating temperature by 1.8 °C for each 1,000 m of altitude.<ref name="omb" /> The 630QB takes 88–128 V or 176–256 V at 47–63 Hz, 8.8 A typical and 12 A maximum at 120 V, and up to 690 W.<ref name="omb" /> Use a grounded wrist strap (DEC 29-11762-00) and grounded work surface inside the enclosure.<ref name="mg8" />

== Configuration rules ==
The order of modules in the backplane matters:<ref name="mg52" />
* The KA630-A CPU always goes in slot 1 (slot 1 of the upper BA23 frame in an H9642).
* MS630-B memory modules go in the slots whose CD rows are interconnected with slot 1: slots 2 and 3 in the BA23-A, 2 to 4 in the BA123-A. MS630-AA modules go in the CD rows of those slots.
* No other dual-height module may go in the CD rows of the slots reserved for memory. Leave them empty if no memory or quad-height option is fitted.
* Total bus loads must not exceed 38 AC or 20 DC loads.<ref name="mg54" />

=== Power budget ===
Add up the +5 V and +12 V current of every module and drive with DEC's figures before adding options. A BA23 supply, or each regulator of a BA123, may deliver up to 36 A at +5 V and 7 A at +12 V, and no more than 230 W in total.<ref name="mg54" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''Power used by MicroVAX II options (DEC Table 5-4, extract)'''
! Option !! +5 V (A) !! +12 V (A) !! Power (W)
|-
| KA630-AA CPU (M7606) || 6.2 || 0.14 || 32.7
|-
| MS630-BB memory (M7608) || 1.8 || 0 || 9.0
|-
| RQDX3 controller (M7555) || 2.48 || 0.06 || 13.2
|-
| TQK50 controller (M7546) || 2.9 || 0 || 14.5
|-
| DEQNA Ethernet (M7504) || 3.5 || 0.5 || 23.5
|-
| DHV11 multiplexer (M3104) || 4.5 || 0.55 || 29.1
|-
| RD53 disk || 0.9 || 2.5 || 34.5
|-
| RX50 diskette || 0.85 || 1.8 || 25.9
|-
| TK50 tape || 1.35 || 2.4 || 33.55
|}
<ref name="mg54" />
In the BA23 only one RD5x fixed disk and one removable drive (RX50 or TK50) fit, and two full-height fixed disks cannot be installed because of the power limit.<ref name="chw" />

== Fans and cooling ==
The H7864 runs the BA23's front and rear fans from +10 V outputs, which a supply jumper raises to +12 V; DEC's thermal and acoustic figures assume 10 V.<ref name="mg14" /> The fans are DEC 12-17556-01, the same part front and rear.<ref name="mg8" /> Restorers find the BA23 fans noisy even at 10 V, with whine from the motors; Warner Losh noted on the cctalk list that noise can come from lubrication and that a quieter fan moving less air is a risk to components that rely on the air flow.<ref name="cc1" /><ref name="cc2" /> When refitting the BA23 rear fan, its cable is not keyed: match the curve of the connector to the curve of the fan housing.<ref name="mg86" /> The BA123 has a 12.7 cm card-cage fan and an 11.4 cm mass-storage fan, both fed with +12 V separate from the main supply outputs, and a temperature sensor above the card cage.<ref name="mg9" /><ref name="mg14c" />

== Time-of-year clock battery ==
The battery backup unit (DEC 12-19245-01) sits in a plastic holder on the CPU distribution insert at the rear. It keeps the KA630's time-of-year clock running with the power off, and the clock chip's RAM holds the console language. When it fails, the console stops and zeroes the clock at power-up, and the operating system finds the clock stopped and needs the time setting again.<ref name="mg3" /><ref name="ka" /><ref name="mg8" /> To replace it in a BA23:<ref name="mg81" />
# Unplug the machine.
# Remove the rear cover and the console cable from the CPU distribution insert.
# Loosen the two screws of the rear I/O panel assembly, swing it open and remove the ground strap screws.
# Disconnect the CPU cables from the insert, noting the red stripe on each.
# Disconnect the battery unit from the insert, spread the plastic holder and pop it out.
In the H9642 the insert is removed first and the battery's red and black leads are disconnected from it.<ref name="mg10" /> Check the old pack and the insert for electrolyte; see [[Battery Explosion, Capacitor or Corrosion Damage]].

== MMS diagnostics ==
DEC's MMS diagnostics load from diskette or tape. Main menu selection 1, "Test the system", is a quick, non-destructive test that DEC suggests anyone can run; selection 2 lists every option the CPU recognises, with ROM revision levels, so a device that is fitted but missing from the list is at the wrong address, faulty or badly connected. The service menu (service version only) includes tests that can destroy data, and DEC reserves it for service staff after the non-destructive tests have failed to find a fault.<ref name="mg6" />

== Preventive maintenance checklist ==
# Check the room against the environmental limits above.<ref name="omb" />
# Clean the fans and check they turn; refit the rear fan cable the right way round.<ref name="mg86" />
# Check the TOY clock battery and the insert for leakage.<ref name="mg81" />
# Check the module order and the power budget after any change.<ref name="mg52" /><ref name="mg54" />
# Run MMS selections 1 and 2.<ref name="mg6" />

== Related pages ==
* [[MicroVAX II]]
* [[MicroVAX II Power Supply Guide]]
* [[MicroVAX II Troubleshooting Guide]]
* [[MicroVAX II Documentation]]
* [[Battery Explosion, Capacitor or Corrosion Damage]]
* [[Hard Drive Maintenance and Repair]]

== References ==
<references>
<ref name="mg">Digital Equipment Corporation, ''MicroVAX II Maintenance Guide'', AZ-GM3AA-MN, first edition October 1985 ([[:File:MicroVAX II Maintenance Guide (AZ-GM3AA-MN).pdf]]).</ref>
<ref name="mg14">DEC, AZ-GM3AA-MN, section 1.4.1, p. 1-23. Fan outputs and jumper.</ref>
<ref name="mg14c">DEC, AZ-GM3AA-MN, section 1.4.2, p. 1-28. BA123 fan and temperature sensor supply.</ref>
<ref name="mg3">DEC, AZ-GM3AA-MN, section 3.2.3, p. 3-11. CPU distribution insert battery backup unit.</ref>
<ref name="mg52">DEC, AZ-GM3AA-MN, sections 5.1 and 5.2. Configuration rules and module physical priority.</ref>
<ref name="mg54">DEC, AZ-GM3AA-MN, sections 5.4 and 5.5, Table 5-4, pp. 5-10 to 5-13.</ref>
<ref name="mg6">DEC, AZ-GM3AA-MN, chapter 6, sections 6.3.1 to 6.3.4.</ref>
<ref name="mg8">DEC, AZ-GM3AA-MN, section 8.1 and Table 8-1, BA23-A FRUs and ESD caution.</ref>
<ref name="mg81">DEC, AZ-GM3AA-MN, chapter 8, time of year clock battery backup removal, Figures 8-35 to 8-37.</ref>
<ref name="mg86">DEC, AZ-GM3AA-MN, section 8.6 and Figure 8-24, rear fan cable.</ref>
<ref name="mg9">DEC, AZ-GM3AA-MN, Table 9-1, BA123-A FRUs.</ref>
<ref name="mg10">DEC, AZ-GM3AA-MN, section 10.3.1, p. 10-4. H9642 battery backup unit removal.</ref>
<ref name="om">Digital Equipment Corporation, ''MicroVAX II 630QB Owner's Manual'', AZ-GLCAA-MN, updated May 1986 ([[:File:MicroVAX II 630QB Owner's Manual (AZ-GLCAA-MN).pdf]]).</ref>
<ref name="omb">DEC, AZ-GLCAA-MN, appendix B, pp. B-3 to B-4. Electrical and environmental requirements.</ref>
<ref name="ka">Digital Equipment Corporation, ''KA630-AA CPU Module User's Guide'', EK-KA630-UG-001, February 1986, section 3.2.4 ([[:File:KA630-AA CPU Module User's Guide (EK-KA630-UG-001).pdf]]).</ref>
<ref name="chw">"BA23 Enclosure", ''Computer History Wiki'', [https://gunkies.org/wiki/BA23_Enclosure gunkies.org/wiki/BA23_Enclosure]. Mass storage limits.</ref>
<ref name="cc1">Mark G. Thomas, "BA23 fan noise", cctalk mailing list, 31 January 2016, [https://www.mail-archive.com/cctalk@classiccmp.org/msg11020.html mail-archive.com].</ref>
<ref name="cc2">Warner Losh, "Re: BA23 fan noise", cctalk mailing list, 1 February 2016, [https://www.mail-archive.com/cctalk@classiccmp.org/msg11035.html mail-archive.com].</ref>
</references>

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