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PDP-11/44 General Maintenance

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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).[1][2] The power supply is covered in PDP-11/44 Power Supply Guide.

Safety

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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.[3] 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.[4] The BA11-A box weighs about 34 kg (75 lb); lift it with care.[5]

Air flow

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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.[6] 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.[7][8] 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 %.[9]

Fans

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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.[10]

Module checks

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  • 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.[11]
  • Check the M7090 console interface jumpers against the terminal in use, and jumper W10, which enables monitoring of the ±12 V memory supplies.[12]
  • The line time clock can be enabled or disabled on the M7096 multifunction module.[13]

Module current

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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.[14]

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

[15]

Battery backup

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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.[3] DEC's installation procedure ends with the H7750's front toggle switch on and both DC ON and BATT lit.[16]

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References

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  1. ↑ 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).
  2. ↑ 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).
  3. ↑ 3.0 3.1 DEC, EK-11044-UG-003, pp. 2-1 to 2-2, Table 2-1.
  4. ↑ DEC, EK-BA11A-TM-003, pp. 2-20 to 2-21, caution and TB1 measurement.
  5. ↑ DEC, EK-BA11A-TM-003, p. 2-1, section 2.1.1, caution.
  6. ↑ DEC, EK-11044-UG-003, p. 1-3, section 1.2.1.
  7. ↑ DEC, EK-BA11A-TM-003, p. 3-12, section 3.2.2.5, temperature sensing.
  8. ↑ 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).
  9. ↑ DEC, EK-11044-UG-003, pp. 1-7 to 1-8, Tables 1-4 and 1-5.
  10. ↑ DEC, EK-11044-UG-003, pp. 5-10 to 5-15, sections 5.3 and 5.4.
  11. ↑ DEC, EK-BA11A-TM-003, p. 4-27, section 4.2.5, backplane removal note.
  12. ↑ DEC, EK-11044-UG-003, pp. 3-12 to 3-13, section 3.3.1.
  13. ↑ DEC, EK-11044-UG-003, p. 3-13, section 3.3.2.
  14. ↑ DEC, EK-11044-UG-003, p. 3-9, section 3.2.2.
  15. ↑ DEC, EK-11044-UG-003, p. 3-9, Table 3-7.
  16. ↑ DEC, EK-11044-UG-003, p. 5-34, section 5.6, steps 21 to 23.
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