Editing PDP-11/44 General Maintenance

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[[File:PDP-11-44 BA11-A mounting box with H7140 power supply (DEC Figure 1-2).png|thumb|right|360px|BA11-A mounting box: air filter behind the bezel, fan assembly and the H7140 supply at the rear (DEC)]]
Routine care of the '''[[PDP-11/44]]''', from DEC's ''PDP-11/44 System User's Guide'' (EK-11044-UG-003) and ''BA11-A Mounting Box and Power System Technical Manual'' (EK-BA11A-TM-003).<ref name="ug" /><ref name="ba" /> The power supply is covered in [[PDP-11/44 Power Supply Guide]].

== Safety ==
The DC OFF position of the keyswitch removes DC power and stops the fans but leaves AC in the system; only unplugging the line cord removes it.<ref name="ugfp" /> The H7140 holds a high DC voltage after power-off: wait five minutes and confirm less than 20 V across TB1 pins 1 and 2 before working inside it.<ref name="baH" /> The BA11-A box weighs about 34 kg (75 lb); lift it with care.<ref name="ba21" />

== Air flow ==
The BA11-A has three fans on a slide that cool the modules and the power supply, and an open-cell foam air filter directly behind the front bezel that can be removed for cleaning.<ref name="ug12" /> Keep the filter clean and the vents clear: the H7140 has an overtemperature sensor on its output heat sink that shuts the supply down, and in a PDP-11X44 cabinet the power controller's control bus carries an overtemperature shutdown from any unit.<ref name="ba33" /><ref name="tmac" /> DEC's operating range for the mounting box is 5 to 50 °C, 10 to 95 % relative humidity; a system with magnetic tape, disc drives or card readers is limited to the PDP-11X44 cabinet's range of 10 to 40 °C and 10 to 90 %.<ref name="ugspec" />

== Fans ==
The fan assembly slides out of the box (DEC's paragraph 5.3) and is powered from connectors J2 and J3 on the power supply board; it must be removed before the H7140 can come out.<ref name="ugrem" />

== Module checks ==
* Keep modules in their slots: DEC's procedures ask for module positions to be noted before the backplane is removed, so that they go back in the same place.<ref name="ba425" />
* Check the M7090 console interface jumpers against the terminal in use, and jumper W10, which enables monitoring of the ±12 V memory supplies.<ref name="ugcim" />
* The line time clock can be enabled or disabled on the M7096 multifunction module.<ref name="ugmfm" />

== Module current ==
Adding options draws on the H7140's +5.1 V output, rated at 120 A less 5 A for every ampere of ±15 V load above 1 A on each.<ref name="ug38" />
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+ '''Module current at +5.1 V (EK-11044-UG-003, Table 3-7)'''
! Module !! +5.1 V
|-
| M7090 console interface || 0.5 A
|-
| M7094 data path || 7.5 A
|-
| M7095 control || 7.5 A
|-
| M7096 multifunction || 5.0 A
|-
| M7098 Unibus interface || 7.0 A
|-
| M7097 KK11-B cache || 6.5 A
|-
| M7093 FP11-F || 7.0 A
|-
| M7091, M7092 KE44-A || 3.1 A, 6.0 A
|-
| M8722 MS11-MB memory || 4.8 A (plus 1 A at +12 V, 50 mA at −12 V and 1.5 A at +5 B)
|-
| M9302 Unibus terminator || 1.5 A
|}
<ref name="ug37" />

== Battery backup ==
If an H7750 battery backup unit is fitted, check the BATT indicator: on when the battery is at least 90 % charged, slow blink while charging.<ref name="ugfp" /> DEC's installation procedure ends with the H7750's front toggle switch on and both DC ON and BATT lit.<ref name="ugbat" />

== Related pages ==
* [[PDP-11/44]]
* [[PDP-11/44 Power Supply Guide]]
* [[PDP-11/44 Troubleshooting Guide]]
* [[PDP-11/44 Documentation]]
* [[Recommended Tools]]

== References ==
<references>
<ref name="ug">Digital Equipment Corporation, ''PDP-11/44 System User's Guide'', EK-11044-UG-003, July 1981 ([[:File:PDP-11-44 System User's Guide (EK-11044-UG-003).pdf]]).</ref>
<ref name="ug12">DEC, EK-11044-UG-003, p. 1-3, section 1.2.1.</ref>
<ref name="ugspec">DEC, EK-11044-UG-003, pp. 1-7 to 1-8, Tables 1-4 and 1-5.</ref>
<ref name="ugfp">DEC, EK-11044-UG-003, pp. 2-1 to 2-2, Table 2-1.</ref>
<ref name="ug37">DEC, EK-11044-UG-003, p. 3-9, Table 3-7.</ref>
<ref name="ug38">DEC, EK-11044-UG-003, p. 3-9, section 3.2.2.</ref>
<ref name="ugcim">DEC, EK-11044-UG-003, pp. 3-12 to 3-13, section 3.3.1.</ref>
<ref name="ugmfm">DEC, EK-11044-UG-003, p. 3-13, section 3.3.2.</ref>
<ref name="ugrem">DEC, EK-11044-UG-003, pp. 5-10 to 5-15, sections 5.3 and 5.4.</ref>
<ref name="ugbat">DEC, EK-11044-UG-003, p. 5-34, section 5.6, steps 21 to 23.</ref>
<ref name="ba">Digital Equipment Corporation, ''BA11-A Mounting Box and Power System Technical Manual'', EK-BA11A-TM-003, August 1983 ([[:File:BA11-A Mounting Box and Power System Technical Manual (EK-BA11A-TM-003).pdf]]).</ref>
<ref name="ba21">DEC, EK-BA11A-TM-003, p. 2-1, section 2.1.1, caution.</ref>
<ref name="baH">DEC, EK-BA11A-TM-003, pp. 2-20 to 2-21, caution and TB1 measurement.</ref>
<ref name="ba33">DEC, EK-BA11A-TM-003, p. 3-12, section 3.2.2.5, temperature sensing.</ref>
<ref name="ba425">DEC, EK-BA11A-TM-003, p. 4-27, section 4.2.5, backplane removal note.</ref>
<ref name="tmac">Digital Equipment Corporation, ''PDP-11/44 System Technical Manual'', EK-KD11Z-TM-001, December 1980, pp. 4-22 to 4-23, power checks ([[:File:PDP-11-44 System Technical Manual (EK-KD11Z-TM-001).pdf]]).</ref>
</references>

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